Magnetochemistry doi: 10.3390/magnetochemistry12100118

Authors: Suliman Mubarak Alshammari H. M. Hamouda Muath Alkadi Mohamed F. Abouelenein Muhna Alshammari Khaled Alharbi Khater A. E. Gad A. E. Elmeshneb Abdalrahman M. Rayan Mahrous R. Ahmed

Herein, high-entropy ferrites (HEFs) represent a transformative frontier in solid-state chemistry and materials physics, shifting design paradigms from conventional mono- or co-substituted ceramics toward multi-component, single-phase solid solutions. Stabilized by a massive configurational entropy (ΔSconf > 1.5 R), these systems incorporate five or more principal cations into a single crystalline matrix, such as cubic spinel (Fd3̅m), perovskite, or hexagonal structures. This comprehensive review systematically evaluates recent breakthroughs in HEF design, tracing the continuous lineage from advanced synthesis methodologies, including modified Pechini sol–gel and hydrothermal routes, to local coordination environments and macroscopic functional expressions. We detail how intense local lattice distortions and polyhedral buckling alter metal–oxygen ligand bond parameters, disrupting traditional collinear A-O-B superexchange pathways to induce quantum magnetic frustration, low-temperature spin-glass behavior, and spontaneous exchange bias effects. Beyond fundamental physics, this work highlights the multi-cation “cocktail effect” across cutting-edge applications, emphasizing its role in high-frequency electromagnetic interference (EMI) shielding, multi-redox heterogeneous catalysis, and high-capacity electrochemical energy storage. Finally, we address current computational bottlenecks in Density Functional Theory (DFT+U) simulations and propose a roadmap for accelerating phase stability predictions and magnetic footprint tuning through the integration of high-throughput workflows and closed-loop, data-driven machine learning architectures. By bridging the gap between thermodynamic theory and targeted application, this review provides a foundational framework for the next generation of entropy-stabilized functional devices.

Magnetochemistry doi: 10.3390/magnetochemistry12100117

Authors: Jaspreet Kaur Grewal Manpreet Kaur Rajeev K. Sharma Aderbal C. Oliveira Vijayendra Kumar Garg Virender K. Sharma

The journal retracts the article titled “Structural and Photocatalytic Studies on Oxygen Hyperstoichiometric Titanium-Substituted Strontium Ferrite Nanoparticles” [...]

Magnetochemistry doi: 10.3390/magnetochemistry12100116

Authors: Nicolaza Pariona Joaquin Garcia Ecson Flores Luz Esmeralda Román Mendoza Noemi Raquel Checca Huaman José L. Solís Monica M. Gómez Marco A. Morales

Efficient water disinfection remains a critical challenge due to the persistence of waterborne pathogens. This study reports the synthesis and characterization of magnetically recoverable Fe3O4-Cu composite nanoparticles designed for efficient water disinfection. The particles consist of magnetite nanoparticles functionalized with metallic copper (Cu0) nanoparticles. The nanoparticles were synthesized via oxidative coprecipitation and characterized using x-ray diffraction, Mössbauer spectroscopy, DC magnetometry and transmission electron microscopy (TEM). Antibacterial assay was conducted against Staphylococcus aureus and Escherichia coli. Rietveld refinements confirmed lattice parameters and crystallite sizes of 8.40 Å (102 nm) for Fe3O4 and 3.62 Å (101 nm) for Cu. The 57Fe Mössbauer spectrum for Fe3O4, at 300 K, exhibited two sextets with isomer shifts and hyperfine magnetic fields of 0.61 mm/s (45.3 T) and 0.34 mm/s (48.9 T), corresponding to Fe2.5+ at octahedral sites and Fe3+ at tetrahedral sites, respectively. The isothermal magnetization at 300 K for Fe3O4 showed hysteretic behavior with saturation magnetization of 80.2 emu/g, remanence of 17.9 emu/g and coercivity of 197 Oe. Antibacterial efficacy was evaluated against Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative) using both the poisoned food method and batch removal assays. Results demonstrated a significant strain-dependent sensitivity; Fe3O4-Cu NPs inhibited S. aureus growth at concentrations as low as 0.1 mg/mL while E. coli required 0.5 mg/mL for similar effects. In batch experiments, 0.5 mg/mL of NPs achieved 100% bacterial removal for S. aureus, whereas 0.75 mg/mL was necessary for E. coli. Furthermore, the magnetic core facilitated rapid separation and reusability; the NPs maintained high efficiency against both strains in a second cycle, showing no significant loss of antibacterial activity. These findings highlight the potential of Fe3O4-Cu nanocomposites as high-performance, reusable biocides for targeted water treatment applications.

Magnetochemistry doi: 10.3390/magnetochemistry12100115

Authors: Xiaogang Yu Fang Yang Peiyan Pei Bao Yang Wenming Xiong Zhuang Li

Self-regulating magnetic induction hyperthermia (SMIH) represents a localized tumor therapeutic modality that utilizes the Curie temperature (Tc) of magnetic nanoparticles (MNPs) to realize the automatic control of the hyperthermia temperature, which has attracted extensive research attention. Although various low-Tc MNPs have been fabricated, three critical challenges hinder the clinical translation of SMIH. Regarding thermal performance parameters, the threshold values of Tc and heating efficiency for effective SMIH remain undetermined. In terms of intratumoral retention, rapid loss and redistribution of intratumoral MNPs severely weaken long-term thermal stability during repeated hyperthermia cycles. From the perspective of manufacturing, large-scale fabrication of well-dispersed low-Tc MNPs is still a technical challenge. This review systematically elaborates on the above three challenges and proposes future research directions to accelerate the clinical transformation of SMIH.

Magnetochemistry doi: 10.3390/magnetochemistry12100114

Authors: Joan-Josep Suñol

Soft magnetic materials are promising candidates for a wide range of applications, including components and devices for energy conversion, filtering, resonance, and magnetic shielding, because of their high-power density and favorable magnetic properties [...]

Magnetochemistry doi: 10.3390/magnetochemistry12100113

Authors: Jiyong Zhang Junchi Lu Zhendong Yin Hongxia Ouyang

Accurate magnetic core loss prediction is important for efficiency evaluation and thermal design in high-frequency power electronic converters. Under varying temperature and frequency conditions, core loss exhibits strong nonlinear behavior, making conventional fixed-parameter Steinmetz-type models difficult to maintain stable accuracy. To address this problem, this work proposes a temperature–frequency-dependent core loss prediction method under triangular-wave excitation by combining the improved Generalized Steinmetz Equation (iGSE), dynamic Fitness–Distance Balance Teaching-Learning-Studying-Based Artificial Bee Colony (dFDB-TLSABC), and a gated recurrent unit (GRU) network. The dFDB-TLSABC algorithm identifies iGSE parameters under different operating conditions, and GRU maps temperature and frequency to the corresponding parameters for dynamic loss calculation. Based on triangular-wave data for N87, 3C90, and 77 ferrites from the MagNet database, the proposed model reduces the average prediction error by at least 61.87% and 61.60% relative to the conventional iGSE model and the Improved Steinmetz Equation (ISE) model, respectively. Compared with Long Short-Term Memory Network (LSTM), Random Forest (RF), Support Vector Machine (SVM), Multi-Layer Perceptron (MLP), and polynomial regression (PR) models, the reductions are 5.91%, 28.50%, 32.26%, 3.80%, and 2.64%, respectively. These results indicate improved prediction accuracy under temperature–frequency variations.

Magnetochemistry doi: 10.3390/magnetochemistry12100112

Authors: Irina E. Stas Olga V. Slatinskaia Natalia N. Rodionova

The structural dynamics of the aqueous hydrogen-bond network under external fields re-main a subject of significant scientific interest. These subtle molecular rearrangements directly dictate macroscopic fluid behavior, bridging network geometry and bulk properties. This study investigates the effects of high-frequency electromagnetic fields (EMFs) in the 30–200 MHz range on the physicochemical properties of ultrapure water and the long-term stability of the induced alterations. The physicochemical modifications of electromagnetically treated water (EMTW) depended more heavily on the treatment frequency than on exposure duration, with the most pronounced changes occurring at 30, 110, and 160 MHz. Specific electrical conductivity (SEC) emerged as the most sensitive indicator of EMF exposure. Notably, the study reveals a durable after-effect, as shifts in SEC persist for up to seven days in pure EMTW, as well as in its mixtures with ultrapure water (1:99, 1:9, and 1:1 by volume). Furthermore, non-contact exposure to EMTW induced a “distant effect,” increasing the SEC of untreated water by up to 36% over a seven-day period. These findings suggest that EMF exposure perturbs localized hydrogen bonding and cluster dynamics, thereby altering hydration shells and ion mobility. Consequently, EMF treatment serves as a powerful method for the targeted modification of aqueous systems.

Magnetochemistry doi: 10.3390/magnetochemistry12100111

Authors: Mehmet Firat Baran Vedat Tümen Serdar Ekinci Mizgin Özaydin Aziz Eftekhari Abdulkadir Levent Fevzi Yaşar Taras Kavetskyy Ondrej Šauša Evgeny Katz Bożena Zgardzińska Davut Izci Rovshan Khalilov Oleh Smutok

The growing demand for sustainable and high-performance energy storage systems has stimulated the development of biomass-derived electrode materials for supercapacitors. In this study, activated carbon (Cm-AC) was synthesized from Crataegus monogyna seeds and combined with magnetic iron oxide (Fe3O4) nanoparticles to fabricate a hybrid Cm-AC@Fe3O4 electrode. The incorporation of iron oxide into the activated carbon matrix altered the charge-storage mechanism from predominantly electrical double-layer capacitance to a hybrid process with a significant faradaic (diffusion-controlled) contribution. Electrochemical measurements in 1 M Na2SO4 showed that the specific capacitance increased from 145.92 to 270.68 F g−1 at a scan rate of 5 mV s−1. Dunn kinetic analysis revealed that diffusion-controlled faradaic processes accounted for up to 87.82% of the total capacitance at low scan rates, consistent with a dominant contribution from reversible Fe2+/Fe3+ redox reactions. Galvanostatic charge–discharge analysis yielded a specific capacitance of 351.51 F g−1 at 0.5 A g−1, while electrochemical impedance spectroscopy demonstrated reduced internal and charge-transfer resistances after Fe3O4 incorporation. A symmetric Cm-AC@Fe3O4 supercapacitor retained 87.5% of its initial capacitance after 10,000 charge–discharge cycles and delivered a maximum energy density of 10.35 Wh kg−1 at a power density of 396 W kg−1. These findings demonstrate that biomass-derived Cm-AC@Fe3O4 is a promising and sustainable electrode material for high-performance supercapacitor applications.

Magnetochemistry doi: 10.3390/magnetochemistry12100110

Authors: Bahram Jalili Hassan Roshani Payam Jalili

Magnetic regulation of ferrofluid transport can modulate heat and fluid motion without mechanical actuation, but the combined effect of field strength and an orientable internal obstacle remains insufficiently resolved. This study numerically examines laminar natural convection of a 1.3 vol% Fe3O4/SWCNT (Single-Walled Carbon Nanotube)–water hybrid ferrofluid in a square cavity containing a rotatable elliptical barrier under a vertical magnetic field. Eight barrier orientations (0–315° in 45° increments) are evaluated at Ra = 103 and Ha = 20 and 80 using the finite element method in COMSOL Multiphysics. The governing formulation was corrected to use a symmetric viscous operator and the Lorentz term associated with a vertical magnetic field; the base-fluid Prandtl number calculated from the tabulated properties is 6.07. An independent, differentially heated square-cavity benchmark reproduced the reference values for maximum horizontal and vertical velocities and the average Nusselt number with relative errors below 0.76%. The computed fields show that barrier orientation controls the locations and signs of the velocity extrema and the pressure range, whereas the reported temperature profiles change comparatively little between the two Hartmann numbers. The 90° orientation gives the minimum reported Bejan number, while 45° gives the maximum. Because Be is a ratio, these extrema identify changes in the relative contribution of thermal irreversibility and do not, by themselves, establish a minimum or maximum of total entropy generation. The results demonstrate a coupled geometric–magnetic redistribution of the local thermohydrodynamic fields and identify 90° as the preferred orientation only under the Bejan-number criterion adopted here.

Magnetochemistry doi: 10.3390/magnetochemistry12100109

Authors: Roman Boča Alina Bieńko Ján Titiš Cyril Rajnák

This study investigates field-supported slow relaxation of magnetization in 48 diverse Co(II) compounds, encompassing 0D, 1D, and 2D systems with coordination numbers 4, 5, and 6. Using AC susceptometry, out-of-phase susceptibility (χ″) was analyzed as a function of frequency, temperature, and DC field. Deconvolution via an extended Debye model reveals three distinct relaxation components: low-frequency (τLF ≈ 1 s), intermediate-frequency (τIF ≈ 1 ms), and high-frequency (τHF ≈ 1 μs) modes. While most complexes follow standard thermal behavior, the research highlights anomalous reciprocating thermal behavior (RTB), where relaxation times unexpectedly shorten upon cooling. By utilizing ln(τ) vs. ln(T) plots, the study points to relaxation mechanisms based on the power law expressed as 1/τ = CTn, including Raman (typically n = 5–9), direct (n = 1, field dependent), phonon bottleneck (n = 2), RTB (n = −1), Orbach (possibly n > 9), and quantum tunneling (n = 0) processes. Findings indicate that the Orbach mechanism is less common than traditionally assumed and that the retrieved experimental barrier (Ueff) is often a fictitious parameter. This study provides a critical reanalysis of the magnetic properties of a selected set of Co(II) complexes, with focus on slow magnetic relaxation.

Magnetochemistry doi: 10.3390/magnetochemistry12100108

Authors: Shuhan Ma Xu Lu Xijiu Sun Yuxi Liu Hongjing Li

Waxy crude oils exhibit poor low-temperature flowability due to wax crystallization and the formation of a three-dimensional gel network, leading to operational challenges in production and transportation. In this work, a series of Fe3O4@ethylene–vinyl acetate (EVA) nanocomposite pour point depressants (F-NPPDs) with different Fe3O4 particle sizes were synthesized via hydrothermal preparation, surface modification, and solution blending. The effects of Fe3O4 particle size on the physicochemical properties, wax crystallization behavior, and low-temperature rheology of a 20 wt% wax model oil were systematically investigated. Results show that all F-NPPDs significantly improve flowability compared to neat EVA. Among the samples prepared, F2-NPPD exhibits the best overall performance, reducing the pour point to 20 °C and markedly decreasing apparent viscosity and gelation temperature. Rheological and DSC analyses confirm that F-NPPDs effectively lower wax crystallization temperature, weaken gel strength, and reduce both storage and loss moduli. Polarized light microscopy reveals that the addition of Fe3O4@EVA transforms wax crystals from dense needle-like structures into dispersed spherical or flower-like morphologies, thereby disrupting the interconnected wax network. The enhanced performance is primarily attributed to Fe3O4-induced heterogeneous nucleation, which increases nucleation density and refines wax crystal size. Particle size is identified as the dominant factor governing performance, while magnetic interactions play a secondary role. Overall, this study demonstrates that tailoring Fe3O4 particle size is an effective strategy to optimize EVA-based nanocomposite pour point depressants for the improved low-temperature flow assurance of waxy crude oils.

Magnetochemistry doi: 10.3390/magnetochemistry12090107

Authors: Jun-Feng Li Qian Chen Lei Zhou Yang Du Zhen Liang

Reliable magnetic-materials screening requires more than a model that performs well within one computational catalogue. We develop and audit a composition-anchored library residual (CALR) protocol for transferring density-functional-theory (DFT) magnetic-moment information across heterogeneous databases. CALR harmonizes moment percentiles within each library, fits a composition-only ridge anchor, and admits a bounded moment residual only when a nested, composition-disjoint bridge test supports improved rank correlation. AFLOW and JARVIS moments are evaluated against experimental Curie temperatures from NEMAD, with a frozen Materials Project snapshot as a third source. On 484 AFLOW-JARVIS bridge compositions, neither directional gate opens: cross-fitted changes in Spearman correlation are +0.0079 (95% interval −0.0027 to 0.0187) and +0.0060 (−0.0125 to 0.0238). The Materials Project-to-JARVIS bridge gives Δrho = 0.0101 (−0.0036 to 0.0250), also returning the composition anchor. Ungated transfer improves one direction but produces negative transfer in the reverse; CORAL and density-ratio weighting underperform the anchor. A fixed-hash semi-synthetic control shows that CALR can activate for a known transferable residual and close for zero, non-transferable, or reversed residuals, although finite-sample false openings remain. CALR is therefore an auditable diagnostic for cross-library magnetic screening and negative-transfer risk, not formal risk control or validated permanent-magnet discovery. We re-ran the Materials Project analysis with current cell atom counts (nsites), traced every aligned key to a selected DFT identifier and experimental DOI, froze a percentile map on common compounds before gating, held out chemical families from training, resampled element-set groups through the full fit/select pipeline, and compared CALR with same-budget target-domain models. The MP gate remains closed after the nsites correction. We state a single protected deployment estimand: Spearman ρ of the frozen ranking versus experimental Tc on composition-disjoint target-library keys. Structure-resolved and aggregation sensitivities leave the headline |M|–Tc Spearman near 0.43. Family-grouped cross-validation lowers the composition-ridge OOF ρ from 0.697 to 0.461. The 484-key bridge is underpowered for the observed residual (forward 80% power requires Δρ ≈ 0.015–0.020). Materials Project reuses 100% of the NEMAD labels already seen in the AFLOW/JARVIS workflow. CALR still equals the composition ridge on every real direction; we state quantitative conditions under which its extra cost would be justified, and the independent library experiment that would be required to claim a practical benefit.

Magnetochemistry doi: 10.3390/magnetochemistry12090106

Authors: Cunhao Lu Fanjie Meng Jian Chen

Core loss is governed by coupled factors, strong nonlinear behavior, and excitation waveform; traditional empirical models often fail to deliver high accuracy under complex operating conditions. Data heterogeneity across waveforms also limits the generalization ability of data-driven models. To address these issues, this paper proposes a waveform-classified Bayesian-optimized artificial neural network (WC-BOANN) core loss prediction model, which combines Random Forest waveform classification with a Bayesian-optimized artificial neural network. Features including form factor, skewness, total harmonic distortion, and differential variance are first extracted from magnetic flux density time series. The Random Forest waveform classification then identifies sinusoidal, triangular, and trapezoidal waveforms automatically. Separate artificial neural network models are built for each excitation waveform, and Optuna-based Bayesian optimization is used to tune the network structure and hyperparameters. The results show that the unclassified Bayesian-optimized artificial neural network (UC-BOANN) performs unevenly across materials, with MAPE values of 9.46%~19.65% and R2 values of 0.9737~0.9857. By contrast, WC-BOANN improves prediction accuracy: on the test sets of four magnetic materials, all R2 values exceed 0.99, all MAPE values are below 3%, the 95-percentile prediction errors are below 7.5%, and the ±10% prediction accuracy (±10% PA) exceeds 99%.

Magnetochemistry doi: 10.3390/magnetochemistry12090105

Authors: Daniel Ramírez-de-Alba José Antonio Pérez-Tavares Pablo Eduardo Cardoso-Avila Luis H. Quintero Merced Martínez-Rosales Jairo Francisco Juárez-Vera Mario Eduardo Cano-González Israel Águila-Martínez Rita Patakfalvi

Magnetite-type iron oxide nano-assemblies are widely investigated because of their strong magnetic response, chemical stability, and tunable surface chemistry. However, the lower-temperature threshold for crystalline spinel formation in polyethylenimine-assisted solvothermal systems remains insufficiently defined. In this work, an FeCl3·6H2O–ethylene glycol–sodium acetate–branched polyethylenimine system was systematically investigated between 150 and 200 °C to determine the onset of magnetite-type spinel formation and its associated physicochemical evolution. Rietveld refinement identified the crystalline fraction of the product synthesized at 150 °C as 60.1 wt.% hematite and 39.9 wt.% goethite, whereas the materials obtained at 160–200 °C were satisfactorily described using a cubic Fd3¯m magnetite-type spinel model. This structural transformation was accompanied by an abrupt increase in saturation magnetization from 0.806 emu g–1 at 150 °C to 62.86 emu g−1 at 160 °C, reaching 79.99 emu g−1 at 200 °C. Temperature-dependent zero-field-cooled and field-cooled magnetization (ZFC–FC) measurements revealed an anomaly within 99–104 K, with a representative derivative maximum near 101 K, assigned to a Verwey-type transition and supporting the presence of magnetite-containing domains. Brunauer–Emmett–Teller surface-area (BET) analysis, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) revealed a concurrent consolidation process involving goethite dehydroxylation, progressive removal or transformation of organic species, reduction in accessible surface area, and the emergence of spherical nano-assemblies from 160 °C onward. Additional PEI-free control syntheses at 160, 180, and 200 °C showed that a well-developed cubic spinel diffraction pattern was not obtained at 160 °C in the absence of PEI, whereas clear spinel reflections emerged at 180 and 200 °C. These results identify 160 °C as the lowest tested temperature for reproducible magnetite-type spinel formation under the investigated PEI-assisted solvothermal conditions and demonstrate that phase transformation, ferrimagnetic ordering, and nano-assembly consolidation are closely coupled.

Magnetochemistry doi: 10.3390/magnetochemistry12090104

Authors: Jundong Guo

Artificial spin ice provides a versatile platform for investigating geometrical frustration and emergent collective phenomena. However, direct visualization and manipulation of individual magnetic moments remain challenging in conventional nanoscale systems. Macroscopic magneto-mechanical analogs offer an alternative approach by enabling direct observation of individual magnetic elements and flexible control of their interactions. Here, we construct a visible frustrated square lattice composed of mechanically confined permanent magnets and investigate the evolution of collective configurations by varying the intra-unit gap l. We find a non-monotonic order–disorder–order evolution as l is varied. This behavior is associated with the competition between intra-unit and inter-unit magnetic interactions, together with the dissipative and metastable nature of the mechanical system. Vertex statistics, spatial correlations, domain-size distributions, and reciprocal-space magnetic structure factors consistently characterize the evolution of the collective states. Positional-uncertainty analysis further shows that the observed evolution is robust against the experimental positioning accuracy. Our results demonstrate that local interaction engineering provides an effective route for controlling collective states in a macroscopic frustrated magneto-mechanical lattice and establish a directly visible platform for exploring interaction competition and metastability in frustrated systems.

Magnetochemistry doi: 10.3390/magnetochemistry12090103

Authors: Selcuk Atalay

Magnetoelectric materials couple magnetic and electrical order parameters and can convert remotely applied magnetic fields into localized electrical responses. At the nanoscale, this functionality is commonly pursued through core–shell architectures in which a magnetostrictive or magnetic core is mechanically coupled to a piezoelectric or ferroelectric shell. The resulting strain-mediated transduction is attractive for biomedical and bioelectronic applications because magnetic fields penetrate biological tissue with comparatively low attenuation, whereas the generated electrical signals can interact directly with charged biomolecules, cell membranes, ion channels, and electroactive tissues. This review critically evaluates magnetoelectric core–shell nanoparticles from a broad biomedical and bioelectronic perspective. The physical basis of direct and converse magnetoelectric coupling is first discussed, with emphasis on nanoscale boundary conditions, magnetic-domain state, ferroelectric polarization, interfacial strain transfer, ionic screening, and nonlinear field dependence. Representative magnetic-core/piezoelectric-shell material families, including ferrite-based, multiferroic-oxide, lead-free piezoelectric, PZT-containing, and polymer-integrated architectures, are compared in terms of magnetic response, piezoelectric activity, chemical stability, biocompatibility, toxicity, and processability. Particular attention is given to CoFe2O4–BaTiO3 (CFO-BTO) as a benchmark magnetoelectric core–shell system, while alternative material combinations are comparatively discussed to reflect the broader diversity of the field. Synthesis and processing strategies, structural and physicochemical characterization, surface engineering, and local or macroscopic magnetoelectric measurement methods are examined together with the artifacts that can complicate quantitative interpretation. Particular attention is paid to particle size, shell thickness, crystallinity, aggregation, colloidal stability, surface chemistry, biomolecular functionalization, and their influence on magnetoelectric performance and biological interactions. The available literature demonstrates substantial progress in magnetically triggered drug delivery and cancer therapy, wireless neural and cardiac stimulation, tissue engineering, immunomodulation, wound healing, multimodal imaging, and related bioelectronic applications. Biosensing is also considered an important emerging direction; however, direct quantitative detection of proteins, nucleic acids, pathogens, and cancer biomarkers using isolated core–shell magnetoelectric nanoparticles remains comparatively underdeveloped. The review therefore distinguishes experimentally established biomedical and bioelectronic functionalities from less mature biosensing concepts and identifies the measurement, safety, clinically relevant magnetic-field exposure, scalable manufacturing, device-integration, and regulatory challenges that must be addressed for translation. A practical roadmap is proposed for developing reproducible, lead-free, biologically stable, and quantitatively characterized magnetoelectric nanoparticle platforms for next-generation wireless biomedical and bioelectronic technologies.

Magnetochemistry doi: 10.3390/magnetochemistry12090102

Authors: Irmak Dulundu Bugra Ayan

Magnetic cell assembly has emerged as a powerful biofabrication strategy that uses externally applied magnetic fields to manipulate and organize living cells with spatial control, enabling the fabrication of scaffold-free multicellular constructs while preserving cell viability and function. Advances in magnetic nanoparticles, cell labeling techniques, and magnetic field engineering have expanded its applications from rapid spheroid formation to the assembly of complex, spatially organized tissues. This review provides a comprehensive overview of the fundamental principles governing magnetic cell assembly, including the generation of magnetically responsive cells, magnetic force-mediated manipulation, and the biological processes driving tissue formation after magnetic assembly. We discuss the major assembly strategies, including magnetic aggregation, levitation, patterning, alignment, and modular tissue assembly, highlighting their underlying mechanisms, representative studies, engineering advantages, and current limitations. Recent progress in musculoskeletal, cardiovascular, neural, and vascular tissue engineering, as well as organoid and assembloid technologies, disease modeling, and drug discovery, is critically evaluated with an emphasis on experimental outcomes and remaining challenges. Particular attention is given to how magnetic cell assembly has evolved from a technique for manipulating individual cells into a programmable platform for organizing living building blocks with increasing structural and biological complexity. Finally, we discuss the key obstacles to clinical translation, including vascularization, tissue maturation, scalability, reproducibility, and standardization, together with future opportunities arising from the integration of magnetic cell assembly with bioprinting, stem cell engineering, microphysiological systems, and artificial intelligence. This review highlights the potential of magnetic cell assembly as an enabling technology that bridges magnetism and biofabrication to engineer next-generation living tissue models.

Magnetochemistry doi: 10.3390/magnetochemistry12090101

Authors: Anton Anikin Anna Motorzhina Stanislav Pshenichnikov Israfil Shamanov Daniya Zinnyatullina Vitalii Salnikov Valeria Rodionova Victor Belyaev Kateryna Levada Larissa Panina

Hybrid magnetic–plasmonic nanoparticles offer a promising platform for cancer therapy by combining localized photothermal heating with nanoscale mechanical stimulation under remote laser irradiation and low-frequency alternating magnetic fields. However, the therapeutic potential of combining these effects remains insufficiently explored. In this study, we investigated the individual and combined effects of photothermal therapy (PTT) and magnetomechanical therapy (MMT) on the viability of Huh7 hepatocarcinoma cells in vitro using two types of layered Au–Fe microdisks (~1000 nm in diameter) with different layer sequences, i.e., Au(10)/Fe(70)/Au(10) (AFA) and Fe(50)/Au(10)/Fe(50) (FAF), where the values in parentheses denote the layer thicknesses in nanometers. The photothermal conversion efficiencies of the AFA and FAF microdisks in agarose were 35% and 53%, respectively, exceeding the values measured in aqueous solutions. After 24 h of incubation, both types of microdisks exhibited low intrinsic cytotoxicity up to concentrations of 100 µg/mL, at which the cell viability was reduced by no more than 7%. Application of either PTT or MMT enhanced cytotoxicity for both microdisk types. PTT was more effective for AFA microdisks, resulting in 29% cell death, whereas MMT showed greater efficacy for FAF microdisks, inducing 17% cell death. Notably, simultaneous PTT and MMT produced the strongest and synergistic therapeutic effect, leading to approximately 50% cell death. These findings demonstrate the potential of hybrid Au–Fe microdisks as multifunctional agents for combined photothermal and magnetomechanical cancer therapy.

Magnetochemistry doi: 10.3390/magnetochemistry12090100

Authors: Zhongxin Li Chengyan Lin Peng Chi

Shale reservoirs are characterized by high tightness and strong heterogeneity; determining the lower limit of movable pore throats is a core scientific issue for reservoir evaluation and development optimization. Targeting shale in the Jiyang Depression, Bohai Bay Basin, this study employed mercury injection capillary pressure (MICP), nuclear magnetic resonance (NMR) combined with centrifugal experiments, and simulated elastic depressurization production tests to investigate the pore throat structure and fluid mobility of three types of dominant lithofacies. The dominant lithofacies in the study area are laminated cryptocrystalline argillaceous limestone, bedded cryptocrystalline argillaceous limestone, and laminated cryptocrystalline calcareous mudstone, with significant differences in mineral composition among the three lithofacies. Laminated cryptocrystalline calcareous mudstone exhibits the smallest average pore throat radius, yet possesses optimal pore throat connectivity and fluid mobilization capability, with uniform pore throat distribution concentrated in the small pore-size range. The two argillaceous limestone lithofacies develop multi-modal pore systems. Elastic depletion production simulation indicates that the lower limit of movable pore throats for the bedded cryptocrystalline argillaceous limestone lithofacies is 34.6 nm under the tested depletion conditions, demonstrating that stress sensitivity can elevate the actual lower limit of movable pore throats by approximately one order of magnitude; this threshold is lithofacies- and condition-specific and requires validation before generalization. The lower limits of movable pore throats for different lithofacies follow the order: bedded cryptocrystalline argillaceous limestone > laminated cryptocrystalline argillaceous limestone > laminated cryptocrystalline calcareous mudstone.

Magnetochemistry doi: 10.3390/magnetochemistry12090099

Authors: Catalin N. Marin

Magnetic fluids, or ferrofluids, occupy a distinctive position at the interface of magnetism, colloid science, fluid mechanics, materials science, and engineering [...]

Magnetochemistry doi: 10.3390/magnetochemistry12090098

Authors: Nadia El Alouani Dahmouni Rafael Ruiz-García Miguel Julve Francesc Lloret José Martínez-Lillo Joan Cano Salah-Eddine Stiriba

The design and the synthesis of molecule-based crystalline salts made up of simple cationic and/or anionic building blocks with multiple, occasionally stimulus-responsive, chemical (host–guest, catalytic, acid–base, or redox) and physical (optical, magnetic, or conducting) properties constitute two major goals in inorganic, organic, organometallic, and coordination chemistries. A deep knowledge of the basic features of molecular and supramolecular interactions that occur in the solid state is needed to progress along these tasks to obtain new advanced multifunctional materials. Inspired by the outstanding research of several groups on magnetic molecular salts from the mid-1970s to the present day, this review offers a personal portrayal of the history of molecular magnetism and molecular electronics and its current evolution toward molecular spintronics and quantum computing. We focus on the well-known families of molecular salts based on paramagnetic tetrathiafulvalenium/tetraselenafulvalenium or tetracyanoethenide/tetracyanoquinodimethanide organic radicals, cyclopentadienide/cyclooctatetraenide metallocenium complexes, and polyhalide/polycyanide, porphyrin/phthalocyanine, oxalate/dithiooxalate, or dithiolene/dithiolate metal complexes with first-, second-, or third-row transition metal (nd, n = 3–5) and lanthanide (4f) ions. This old but evergreen class of magnetic molecular salts provides illustrative “textbook” examples of advanced multifunctional materials such as molecular magnets and conductors, molecular magnetic conductors, molecular nanomagnets, and molecular quantum bits with potential nanotechnological applications in quantum information storage and processing.

Magnetochemistry doi: 10.3390/magnetochemistry12090097

Authors: Dongxia Ren Hua Wei Wenda Fu Shijie Mu Wenting Wang Longfei Yang

Bacterial contamination remains a critical safety concern in platelet transfusion, and there is an urgent demand for decontamination technologies that eliminate contaminating bacteria without damaging platelet viability and physiological function. Herein, Fe3O4-QCS-PEI-Cu-apt microparticles with enlarged magnetic cores were rationally fabricated to improve aptamer immobilization, aiming at targeted bacterial elimination via near-infrared (NIR) irradiation while maintaining platelet function. Fluorescence assays confirmed their specific targeting capability toward Staphylococcus aureus (S. aureus) without binding to platelets. Magnetic separation experiments demonstrated that the aptamer-functionalized microparticles could efficiently capture and remove 91.35% of S. aureus from platelets. NIR irradiation of the Fe3O4-QCS-PEI-Cu core induced marked bactericidal activity against S. aureus in suspension, as determined by plate counting and LIVE/DEAD staining. This antibacterial ability originated from the intrinsic photo-responsive property of the composite rather than from aptamer-mediated recognition, and could be easily extended to bacteria captured by aptamer-functionalized particles. Comprehensive biocompatibility evaluations, including morphological observation, hematological parameter analysis, CD62P expression detection, and thromboelastography (TEG) were performed. And the results demonstrated that there were no significant changes in platelet morphology, count, activation state, or overall hemostatic function, apart from an increase in the α angle. This platform achieves efficient targeted NIR-triggered antibacterial efficacy while maintaining excellent platelet compatibility, offering a promising strategy to enhance the safety of platelet transfusion.

Magnetochemistry doi: 10.3390/magnetochemistry12090096

Authors: Jun Cai Yu Xia Wenliang Hu Guodong Zhang Yubing Liu Gong Zhang

Oil-based mud filtrate (OBMF) invasion significantly alters the petrophysical response of nuclear magnetic resonance (NMR) logging, severely compromising the accuracy of reservoir fluid identification and petrophysical evaluation. However, the NMR relaxation behavior of OBMF under elevated temperatures (up to 100 °C) and low-frequency (<2 MHz) conditions remains poorly understood. In this study, temperature-dependent NMR experiments were conducted from 30 °C to 100 °C at a fixed frequency of 21 MHz, while frequency-dependent experiments were performed from 1 MHz to 21 MHz at 30 °C. Using combined analysis of T2 spectra and T2-T1 two-dimensional spectra, the effects of temperature and magnetic field frequency on the relaxation characteristics of OBMF were investigated under the conditions of this study. The results show that increasing temperature shifts the T2 distribution toward longer relaxation times, with the T2 geometric mean increasing from 35 ms to approximately 113 ms, exhibiting an exponential relationship (R2 = 0.996). T1 values increase from 368 ms to 589 ms, while the T1/T2 ratio decreases from 11.2 to 5.8. In contrast, decreasing frequency prolongs T2 relaxation times, with the T2 geometric mean following a power-law relationship with frequency. Based on these experimental findings, a dual-parameter model incorporating both temperature and frequency was established for OBMF. The proposed model serves as a theoretical reference for the analysis and correction of NMR logging data acquired under oil-based mud invasion conditions.

Magnetochemistry doi: 10.3390/magnetochemistry12090095

Authors: Zhen Yang Zhenze Zhang Xuecheng Sun Chong Lei

Multilayer graphene-coated Co-based amorphous wires were fabricated by repeated PMMA-assisted transfer processing. Torsional deformation was introduced at different stages of shell construction to investigate the influence of fabrication sequence on the giant magnetoimpedance (GMI) effect. For the non-torsion series, the maximum GMI ratio increased from 165% for the as-spun wire to 302% after three graphene-coating cycles. A further enhancement to 353% was achieved when torsion was introduced after partial shell formation, whereas only a marginal improvement was observed when torsion was applied to bare amorphous wires. Magnetic measurements revealed concurrent reductions in coercivity and peak field together with a systematic evolution of the optimal operating frequency. These correlated changes suggest that progressive shell construction modifies the near-surface magnetic state via electromagnetic boundary modulation, while torsion introduced after partial shell formation provides additional interfacial strain tuning of the graphene-modified near-surface magnetic state, further optimizing low-field circumferential permeability. The results indicate that fabrication-sequence control provides an effective approach for tailoring the GMI response of composite amorphous wires and offers potential for the development of high-sensitivity magnetic sensing devices.

Magnetochemistry doi: 10.3390/magnetochemistry12090094

Authors: Xichun Zhong Zhongyuan Hao Xuan Huang Dongling Jiao Cuilan Liu Juan Cheng Raju V. Ramanujan

La0.8Ce0.2Fe9.2Co0.6Si1.2/Fe bulk composites were fabricated via spark plasma sintering (SPS), and the effects of Fe powder content on the phase composition, microstructure, magnetic properties, mechanical properties, and thermal conductivity of the composites were investigated. The Fe powder content alters the α-Fe phase content in the composites. During SPS, atomic diffusion occurs between the Fe powder and the La0.8Ce0.2Fe9.2Co0.6Si1.2 matrix, which reduces the compositional homogeneity of the desired 1:13 phase and induces the formation of thermal decomposition (TD) structures in particles adjacent to the Fe powder. As Fe powder content increases from 0 wt% to 15 wt%, the maximum magnetic entropy change ((−ΔSM)max) of the composites decreases from 8.11 to 5.78 J∙kg−1∙K−1 under 2 T. Interestingly, the α-Fe phase significantly enhances the mechanical strength and thermal conductivity (λ) of the composites. The composite with 15 wt% Fe (S15) forms a continuous α-Fe network structure and possesses the best mechanical and thermal properties: the (σbc)max reaches 1463 MPa, and the λ at 300 K is 20 W·m−1·K−1. Owing to their balanced magnetic, mechanical, and thermal performances, the La0.8Ce0.2Fe9.2Co0.6Si1.2/Fe composites exhibit distinctive and balanced properties, making them promising candidates for near-room-temperature magnetic refrigeration applications.

Magnetochemistry doi: 10.3390/magnetochemistry12080093

Authors: Juan C. Buitrago Diaz Edwin G. Castro Rodas Carolina Ortega-Portilla Juan E. Bedoya-Rodriguez Daniel Salazar Manuel G. Forero Jeferson Fernando Piamba

Magnetic shape memory alloys based on the Ni–Mn–Ga system are of strategic interest for aerospace and robotics applications due to their ability to respond to both thermal and magnetic stimuli. However, the NASA Shape Memory Materials Database a key resource for the community exhibits significant gaps in functional parameters, with up to 93.7% of records missing critical properties such as the Curie temperature, and over 88% lacking complete magnetic data. To address this limitation, this study proposes a data imputation strategy based on a stacking ensemble comprising twelve machine learning models (LGBM, XGBoost, CatBoost, GradientBoosting, RandomForest, MLP, BayesianRidge, KNN, SVR, GPR, MICE, and AutoEncoder), optimized via Optuna and evaluated using ten random seeds with 10 repetitions each. The approach was applied to reconstruct missing entries in NASA’s database. For heat treatment 1, the method achieved coefficients of determination (R2) of 0.95 for duration (h) and 0.88 for temperature (°C), respectively. For the phase transformation temperatures (Mf, Ms, As, and Af), the method yielded R2 values of 0.83, 0.82, 0.79, and 0.80, respectively. Magnetic properties saturation magnetization and maximum magnetic field were imputed with an R2 of 0.92. In contrast, the Curie temperature exhibited limited predictive performance (R2 = 0.15–0.35), primarily due to insufficient data availability. Overall, the proposed methodology integrates machine learning based imputation with physically supported constraints, providing a viable alternative to enhance the completeness and utility of materials databases.

Magnetochemistry doi: 10.3390/magnetochemistry12080092

Authors: Andy D. Zapata-Escobar Alejandro F. Maldonado Gustavo A. Aucar

We studied the electronic origin of the NMR nuclear magnetic shieldings (σ) of compounds containing the following transition metal atoms: M= Zn, Cd, Hg, Co, Rh, Cr, Mo, W. The electronic mechanisms that underlie the relativistic effects on those shieldings were assessed with the LRESC–Loc model, which permits one to quantify the set of leading relativistic electronic mechanisms responsible for such effects in terms of well-known non-relativistic operators, and also allows for the determination of which molecular orbitals (MOs) are involved in each of those mechanisms. These MOs are such that the chemist’s intuition associated with core, lone-pair (LP), and bonding MOs is satisfied. The LRESC model is a reliable semi-relativistic methodology that has been shown to reproduce, in a semiquantitative manner, the magnetic shieldings and experimental chemical shifts of transition metals in a large set of molecules. Several new features appear in the shieldings analyzed. Trends in the total shieldings within a given family of compounds depend on relativistic effects—the spin-orbit mechanism is one of the most involved—though, within it, one must consider the Fermi contact (FC) and the spin-dipolar (SD) mechanisms. We found that the contributions that are due to partially filled d atomic orbitals (AOs) become too large when the electron correlation is not properly included. This is overcome in our case using density functional theory. A large influence of lone-pairs of π-type on σ(M) is also seen in some of the molecules studied.

Magnetochemistry doi: 10.3390/magnetochemistry12080091

Authors: Shuang Chen Zhongqiu Fu Kang Wang Gongyu Ji Cheng Liu

Pure Fe soft magnetic composites (SMCs) hold a prominent position in cost-sensitive 10–100 kHz medium-to-low-frequency power devices owing to their low raw-material expenditure and high saturation magnetisation. Nevertheless, the inherently poor interparticle electrical resistivity permits the formation of contiguous conduction paths under alternating magnetic fields, giving rise to marked eddy-current dissipation and localised thermal accumulation. To surmount this limitation, the present work introduces γ-mercaptopropyltriethoxysilane (KH580)-functionalised silicon nitride (Si3N4) nanosheets as a multifunctional interfacial regulating layer that simultaneously establishes an electrically insulating barrier and a thermally conductive network on the surface of Fe particles. The structural integrity, surface chemical speciation and deposition behaviour of Si3N4-s nanosheets on Fe particles were systematically examined, and correlations among lamellar coverage completeness, interfacial bonding robustness and the coupled electrical–magnetic–thermal response were elucidated. The findings reveal that KH580 silanisation introduces a surface functional layer while preserving the parent α-Si3N4 crystal structure, and XPS analysis suggests possible local N–Fe and Fe–S interfacial interactions between Si3N4-s and the Fe surface. At a loading of 4 wt.% Si3N4-s, a comparatively continuous and uniform lamellar coating develops on the Fe particle surfaces. The corresponding Fe/Si3N4 SMCs exhibit the highest volume resistivity and a peak thermal conductivity of approximately 12.1 W·m−1·K−1, while maintaining a core loss of approximately 600.2 kW·m−3 at 50 mT and 100 kHz. These results indicate that the 4 wt.% specimen provides the most favourable overall balance among electrical insulation, magnetic response, core-loss suppression and thermal transport within the investigated composition range, furnishing a functionalised lamellar interfacial engineering strategy for performance advancement of low-cost Fe-based SMCs.

Magnetochemistry doi: 10.3390/magnetochemistry12080090

Authors: Emilio Escrivà José Martínez-Lillo

Two diastereoisomers of bis(mepirizole)bis(isothiocyanato-κ,N)cobalt(II) (1 and 2) are isolated from the reaction of cobalt(II) thiocyanate and mepirizole, depending on the crystallization solvent (ethanol, 1; acetonitrile, 2). In both crystal structures, the Co(II) ions exhibit distorted octahedral [CoN4N′2] environment. The analysis of the packing frameworks shows a cooperative relationship between non-classical H-bonds C(sp3)-H···X (X = N, O, S, π) and π-hole bonds, which control the arrangement of the supramolecular 3D networks. The values of the shortest intermolecular metal–metal separation are 8.584(2) Å in 1 and 8.249(1) Å in 2. Both diastereoisomers exhibit magnetic behavior typical of mononuclear Co(II) systems with significant zero-field splitting (ZFS) values, with D being 75.8(1) and 52.9(2) cm−1 for 1 and 2, respectively. Q-band EPR studies confirm the positive value for the D parameters for both compounds. Alternating current dynamic susceptibility measurements show that 1 and 2 exhibit field-induced slow relaxation of the magnetization, which is reminiscent of single-ion magnet (SIM) behavior.

Magnetochemistry doi: 10.3390/magnetochemistry12080089

Authors: Tianyang Cao Yiyue Cheng Ziwu Wang Chao Zhou Chun Zhang

The helical-channel magnetohydrodynamic (MHD) thruster is a silent underwater propulsion device free of rotating mechanical components, which fundamentally eliminates the inherent mechanical noise induced by blades and shaft systems in conventional propeller-driven thrusters. Taking a 10 T-class superconducting helical-channel MHD thruster as the research object, this work establishes a three-dimensional numerical simulation model with bidirectional electromagnetic-fluid coupling via Maxwell–Fluent, filling the research gap of systematic optimization of helical pitch angles in existing low-magnetic-field numerical investigations. A composite magnetic circuit configuration consisting of main coils and compensation coils is adopted, achieving a magnetic field uniformity of 90.13% within the effective working section and markedly alleviating magnetic field attenuation at both ends of the flow channel. Three schemes with helical pitch angles of 23.00°, 17.66°, and 14.29° are quantitatively compared to analyze the effects of helical pitch angle on current density, static pressure, total pressure, radial/axial flow velocities and three-dimensional helical streamlines. Under the rated design mass flow rate of 15.5 kg/s, the scheme with the small pitch angle of 14.29° delivers a thrust of 262.56 N and an electromagnetic efficiency of 7.23%; compared with the large pitch angle scheme of 23.00°, its thrust is improved by 28% and electromagnetic efficiency rises by 53%. Reducing the helical pitch angle extends the effective coupling distance between seawater and the electromagnetic field, optimizes the uniformity of radial current distribution, suppresses eddy currents and Joule heat loss, converts more electromagnetic energy into fluid pressure energy, and thus greatly improves the energy utilization efficiency of the propulsion system. This study provides quantitative design references for the structural optimization and engineering prototype development of low-noise superconducting underwater propulsion equipment, and supports the engineering application of helical-channel magnetohydrodynamic thrusters.

Magnetochemistry doi: 10.3390/magnetochemistry12080088

Authors: Rengang Shi Xinmin Ge Ju Ge Yiren Fan Yiguo Chen Falong Hu Cheng Zhai

Low-field nuclear magnetic resonance (NMR) is widely used for nondestructive characterization of petroleum-related porous media, including pore-structure evaluation, fluid identification, relaxation analysis, wettability assessment, and displacement monitoring. Conventional NMR signal models usually rely on the quasi-static approximation, in which the detected magnetic field is assumed to respond instantaneously to Bloch-governed nuclear magnetization. However, classical electrodynamics requires electromagnetic fields generated by time-dependent magnetization sources to depend on the source state at a retarded time. In this study, a retarded magnetic-dipole formulation is developed to evaluate finite-propagation-time effects in low-field NMR signal modeling. The analysis shows that the correction appears mainly as a phase shift governed by the dimensionless parameter ϵ=ω0L/v, where ω0 is the Larmor angular frequency, L is the characteristic source–receiver distance, and v is the effective electromagnetic propagation velocity, with v=c in free space. Relaxation-induced amplitude corrections are generally smaller. Numerical examples demonstrate that the quasi-static approximation is well justified when ϵ≪1, as typically satisfied in laboratory core NMR. For extended-scale configurations, including unilateral, borehole, underground, and surface NMR, larger propagation paths and medium-dependent electromagnetic properties may increase \epsilon and produce systematic phase deviations. This work provides a theoretical criterion for assessing the validity range of the quasi-static approximation in low-field NMR applications for petroleum-related porous media.

Magnetochemistry doi: 10.3390/magnetochemistry12080087

Authors: Mingjing Gui Xuewen Shi Maojie Liao Dongjun Zhang Yingying Ma Gong Zhang

To study the effect of particle size on nuclear magnetic resonance (NMR) pore characterization of sandstone, core samples were gradually crushed into five particle sizes and the transverse relaxation time (T2) spectrum and NMR response characteristics of the crushed samples were measured. The experimental results show that within the particle size range of 2.4 mm, the T2 spectrum position, T2 mean value, and NMR porosity of sandstone cuttings are basically consistent with the core samples. When the particle size is 1.2 mm, the right peak amplitude of the T2 spectrum increases significantly, and the T2 mean value representing the T2 spectrum characteristics becomes larger, which is presumed to be related to the increase in particle surface water. A comparative analysis suggests that cuttings with particle sizes larger than 2.4 mm can accurately characterize the NMR response characteristics of core samples.

Magnetochemistry doi: 10.3390/magnetochemistry12080086

Authors: Roberta Sorhaia Samayara Sousa Rocha de França Rosangela Maria Ferreira da Costa e Silva Ângela Leão Andrade Daniel de Lima Silva Rubens Lucas de Freitas Filho Vinicius Veríssimo de Carvalho Guilherme Oliveira Siqueira Guilherme Jorge Brigolini Silva Thiago Maturana Ribeiro Diana Quintão Lima José Agenor Carvalho Junior Claudia Andrea Lima Cardoso Vinicius de Oliveira Ribeiro Leila Cristina Konradt-Moraes Rozanna Marques Muzzi

Techniques such as adsorption have been widely adopted to remove residual microplastics (MPs) because they are efficient at removing contaminants from aqueous environments. In this study, we report a novel, low-cost, biodegradable, and scalable biocomposite (LCMAG NaOH) derived from Luffa cylindrica fruit (LC) and micrometric natural magnetite (MAG), prepared without organic solvents, for the removal of MPs. The performance of LCMAG NaOH was evaluated for the removal of polystyrene (PS) and polyethylene terephthalate (PET) MPs, with particle sizes ranging from 75 to 600 µm in three distinct aqueous media: drinking water, simulated seawater, and water collected from the eutrophic lake of Dourados, MS, Brazil. The material was also evaluated for capture capacity and for reutilization in drinking water over three cycles, using a neodymium magnet. The biocomposite exhibited maximum removal capacities of 163 mg g−1 and 158 mg g−1 for PS and PET, respectively, in drinking water. Additionally, it demonstrated high magnetic recovery efficiency (>90% of the initial mass) and good reusability after immersion (10 and 20 min) and a dry step during the first cycle.

Magnetochemistry doi: 10.3390/magnetochemistry12080085

Authors: Hai Liu Jinhua Zhu Xinglian Song Wenju Liao Yu Liu Ke Sun

Spin-spray deposition is a low-temperature route for preparing crystalline ferrite films, but the actual liquid-film temperature has not been isolated from the nominal heater temperature. NiZn ferrite films were deposited at liquid-film temperatures of 87.6, 90.1, 92.7, and 95.0 °C. As the temperature increased, the (222) Lotgering factor fL decreased from 0.32 to 0.01, the triangular morphology weakened, and the growth rate declined. Ms remained nearly constant at 429–442 kA m−1, whereas μ′max increased from 44 to 83 and fr decreased from 465 to 260 MHz. The structural and magnetic trends are consistent with a shift from surface-confined (222)-oriented growth toward less-oriented growth and a corresponding permeability–frequency trade-off. Unlike our previous studies of substrate and oxidant effects, this work isolates the measured liquid-film temperature and establishes its quantitative relationship with texture and dynamic magnetic response. This parameter provides a practical means of selecting the operating window of spin-sprayed NiZn ferrite cores for integrated high-frequency inductors.

Magnetochemistry doi: 10.3390/magnetochemistry12080084

Authors: Yao Ying Yihao Zhu Jingwu Zheng Jing Yu Liang Qiao Juan Li Naoki Wakiya Shenglei Che

In this work, the SiO2-added MnZn power ferrites have been prepared by the conventional ceramic method, and the effect of stress on initial permeability and power loss has been investigated. With increasing SiO2 content, initial permeability firstly increases and then decreases, whereas power loss firstly decreases and then increases. The sample with 50 ppm SiO2 additive exhibits optimal magnetic performance, including the highest initial permeability and the lowest power loss. This optimal sample also exhibits the wide-temperature characteristics of power loss. Initial permeability decreases and power loss increases under the applied stress. The sample with 75 ppm SiO2 additive exhibits the best stress insensitivity of initial permeability and power loss. Through the loss separation method, it is revealed that magnetic hysteresis loss is more sensitive whereas eddy current loss remains almost unchanged with stress. An appropriate addition of SiO2 reduces the stress sensitivity of the initial permeability and power loss of MnZn ferrites.

Magnetochemistry doi: 10.3390/magnetochemistry12080083

Authors: Xu Dong Wenqi Shi Xueying Shi Peidong Liu Jiahui Zhang Zhiyuan Chen Jingjie Zhang

Fracture size governs fluid mobility in shale, yet its direct quantification remains challenging. Nuclear Magnetic Resonance (NMR) transverse relaxation time (T2) offers a unique, non-destructive probe of fracture size distributions; however, a physically grounded conversion from transverse relaxation time to pore radius r (T2−r) is essential to translate NMR signals into quantitative geometric constraints on fluid mobility. This study introduces a capillary-constrained experimental method for T2−r transformation into shale fractures. The workflow uses computed tomography (CT) scanning to extract fracture geometry. The gas-displacing-water process is precisely controlled by integrating the pore capillary pressure and back-pressure feedback algorithm. The NMR-CT conversion method performed in this study differs significantly from the T2−r transformation based on conventional MICP. Differential spectral analysis isolates fracture-specific T2 responses, and least-squares fitting derives the T2−r conversion. Constraining displacement pressure and controlling segmental pressure are effective methods for ensuring the accuracy of fracture displacement. By emphasizing the governing role of capillary pressure during displacement, this method achieves accurate fracture-targeted displacement and reliable T2−r mapping. The results significantly advance the use of NMR for quantifying fracture size and evaluating fluid transport in shale.

Magnetochemistry doi: 10.3390/magnetochemistry12080082

Authors: Kawtar Khattab Abdellah El Boukili Lahcen Boudad Jacem Zidani Naji AlDahoudi Arash Jamali Mimoun El Marssi Mohamed Saadi M’hamed Taibi Abdelilah Lahmar

This study analyzes the structural and magnetic properties of a new composite material with a lithium borate glass matrix loaded with electric arc furnace slag, with a composition of 50Li2O-50B2O3-80 wt.% slag. The amorphous nature of the obtained glass is confirmed by X-ray diffraction analysis (XRD). Differential scanning calorimetry (DSC) indicates that the material has an extremely high thermal stability as evidenced by its high glass transition temperature which is due to the reinforcing role of the slag metallic oxides. Additionally, magnetic studies reveal a highly frustrated magnetic state in the disordered system. The significant addition of mixed-valence iron ions (Fe2+/Fe3+) in the slag forms antiferromagnetic interactions in the system. These factors result in the stabilization of the spin-glass-like state. The incorporation of slag within the lithium borate matrix is a promising route to valorize this industrial by-product and to develop new functional materials.

Magnetochemistry doi: 10.3390/magnetochemistry12080081

Authors: Muhamad Fouad

The Zeta-Minimizer Theorem provides a fully deductive variational foundation for the hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR) in proton exchange membrane fuel cells. Starting from three primitive thermodynamic axioms and the helical geometry of the phase functional, a multi-extent dynamical system is constructed that simultaneously treats the electrochemical reaction coordinates and the adsorption extents of the participating species at the solid–electrolyte interface. The combined Hessian of the phase functional yields a complete spectrum of relaxation rates whose eigenvalues and eigenvectors emerge directly from the solid blackbox constants Ck and the helical partition functions of the reactive species. Adiabatic elimination of the fast surface modes produces an effective single-extent description in which voltage (or overpotential) appears as the conjugate variable, exactly analogous to the role of pressure in the corresponding gas-phase ammonia synthesis framework. The resulting nonlinear rate law is thermodynamically consistent at all conditions, recovers the Butler–Volmer and Tafel forms as well-defined limiting cases, and incorporates the effects of temperature, dilution, and catalyst-specific interface constants without empirical activation energies or adjustable reaction orders. The framework therefore unifies equilibrium, kinetics, and modal dynamics of HOR and ORR within a single variational structure, offering a parameter-light, first-principles alternative to classical empirical electrocatalytic rate expressions while preserving transparent contact with established limiting laws.

Magnetochemistry doi: 10.3390/magnetochemistry12070080

Authors: Elena V. Fomenko Yuriy V. Knyazev Galina V. Akimochkina Leonid A. Solovyov Natalia N. Anshits Sergey V. Semenov Andrey A. Dubrovskiy Anna V. Lukyanenko Andrey V. Tsarenko Elena V. Mazurova Ekaterina D. Smorodina Oleg A. Bayukov

Dispersed ferrospheres (FSs) are a valuable component of coal fly ash, whose application potential is determined by their microspherical design, fine particle size, and high concentration of magnetic iron compounds. This study proposes an efficient technological scheme for extracting dispersed FSs from high-calcium fly ash, comprising (i) aerodynamic classification and (ii) dry magnetic separation. The isolated fractions were characterized, including determination of the particle-size distribution, morphology, chemical and phase composition, Mössbauer parameters, magnetic properties, and surface distribution of magnetic phases. It was shown that the average particle diameters of the FS narrow fractions are 3 and 8 µm. The major chemical components are FeO, CaO, and SiO2, whose total content amounts to 81–83 wt %. Regarding the phase composition, Fe-spinel and calcium ferrites are predominant, accounting for 38–46 and 13–16 wt %, respectively. The efficiency of the proposed process for extracting FSs reaches the level achieved by conventional wet magnetic separation. The saturation magnetization of the dispersed FS samples increases by more than an order of magnitude (up to 23–28 emu/g) compared to the initial fly-ash fractions (1.7–1.8 emu/g). For the first time, magnetic topography investigation of single microspheres directly demonstrates that the surface of the aluminosilicate matrix is enriched with magnetic microcrystals formed during coal combustion. The obtained results may prove useful in the design of functional materials with magnetically active surfaces for advanced applications.

Magnetochemistry doi: 10.3390/magnetochemistry12070079

Authors: Jiawen Xu Yanlu Hu Juan Li Jie-Xiang Yu Rujun Tang

In this work, gradient-sized Pr6O11 powders were fabricated via a wet ball-milling method with variable milling durations. The microstructural evolution and temperature-dependent magnetic properties of different Pr6O11 powders were systematically investigated. The results reveal that wet ball-milling effectively refines powder particle size and introduces controllable lattice defects without altering the intrinsic crystal structure. Magnetic measurements over a temperature range of 3–300 K demonstrate that the unmilled powder exhibits typical paramagnetic behavior. However, milling-induced particle refinement significantly enhances the low-temperature magnetic moments of Pr6O11, accompanied by characteristic superparamagnetic hysteresis at 3 K. Furthermore, the fitted paramagnetic Curie temperature θp and Curie constant C confirm that the magnetic regulation is milling-affected and dependent on milling time. Prolonged milling above 1 day cannot continuously increase low-temperature magnetic moments. The above temperature-dependent magnetic properties of milled Pr6O11 can possibly be attributed to milling-induced grain refinement and lattice distortion, as supported by the microstructure analysis. This work provides valuable physical insights into the low-temperature magnetic properties of Pr6O11 and offers guidance for its magnetic functional applications.

Magnetochemistry doi: 10.3390/magnetochemistry12070078

Authors: Xu Dong Yu Zeng Jiawei Tang Xueying Shi Wenqi Shi Wenting Liu

Pixel-level identification of whole-rock mineral components in shale scanning electron microscopy (SEM) images is essential for characterizing shale-reservoir microstructures and quantifying mineral contents. Existing mineral identification algorithms generally cannot identify all whole-rock mineral components within a unified framework. Their overall accuracy is also limited by class imbalance, and fine-grained minerals and mineral boundaries remain difficult to segment in complex lithological backgrounds. To address these limitations, shale samples from the Lianggaoshan Formation in the Sichuan Basin were investigated, and a dynamic attention Transformer (DAM-Transformer) was developed for whole-rock mineral component identification in shale SEM images. The proposed method (1) integrates the matrix and associated minerals into a unified segmentation framework; (2) employs a hybrid loss function tailored to the feature distribution of shale SEM images to mitigate class imbalance and improve training stability and model generalizability; and (3) introduces a dynamic attention mechanism that adaptively optimizes window attention weights, focuses on mineral target regions, enhances boundary detail features, and suppresses background noise. The DAM-Transformer achieved a pixel-level mean accuracy (mAcc) of 78.12% across ten mineral classes, outperforming Mask2Former, FCN, UPerNet, DeepLabV3+, and other benchmark methods by 1.51–8.92%. Visual comparisons further demonstrated that the proposed method preserves the continuity of major mineral regions and substantially improves the identification of fine-grained minerals and complex mineral boundaries. In addition, application analysis of shale plug samples showed that the mineral contents identified by the DAM-Transformer exhibited clear response relationships with saturation–centrifugation NMR parameters, providing quantitative support for interpreting shale pore structure, fluid occurrence, and reservoir properties.

Magnetochemistry doi: 10.3390/magnetochemistry12070077

Authors: Haitian Xu Yutong Chi Hujun Wang Shengjie Zhang Jiahao Dong Yijian Wei Hongchao Cui Yanwen Li Zhenkun Li

Integrating the “programmable” characteristics of smart materials with 3D printing technology enables the integration of structural design and manufacturing, showing broad application prospects in flexible electronics, aerospace, biomedicine, and other fields. Magnetically controlled smart fluids are characterized by flexible solid–liquid conversion, high driving efficiency, and high safety. By harnessing the distinctive characteristics of this material, manufacturing and actuation approaches for intelligent structures can be further diversified. Inspired by the sol–gel transformation mechanism of protoplasm, this paper proposes a composite 3D printing method for magnetic and non-magnetic materials. A magnetically controllable binary suspension system with strong thixotropic properties was constructed, and its microscopic self-assembly structure was characterized. The yield behavior, linear viscoelastic properties, and thixotropic recovery performance of the magnetic thixotropic fluid (MTF) were investigated through steady and dynamic rheological measurements, and the optimal rheological parameters for printing were determined. A 3D printing platform with coordinated control of a magnetic field and a motion system was built to further study and optimize the printing process. The supporting characteristics of the MTF on a silicone film and the deformation of the printed composite structure under a gradient magnetic field were studied. The composite 3D printing and its application in soft robotics may provide new insights for space exploration, biomedicine, military reconnaissance, and many other fields.

Magnetochemistry doi: 10.3390/magnetochemistry12070076

Authors: Ruyun Ding Jiayu Qin Weihan Wang Shijie Yang Rui Wu Hui Zheng Liang Zheng

Multicomponent ferrite oxides with mixed valence states and tunable oxygen-defect chemistry are promising active materials for low-power memristive synapses. In this work, Ag/Ni0.3Cu0.2Zn0.5Co0.005Mn0.005Fe1.99O/Ag memristors were fabricated by pulsed laser deposition, and the effects of post-deposition annealing at 700–900 °C on film structure, chemical states, magnetic behavior, resistive switching, and synaptic performance were investigated. The film annealed at 800 °C exhibited a dense surface morphology, improved crystallinity, and uniform elemental distribution. X-ray photoelectron spectroscopy confirmed the coexistence of Fe2+/Fe3+ states and oxygen-related defect components, indicating the presence of oxygen vacancies. Room-temperature magnetic hysteresis measurements revealed ferrite-type magnetic behavior in the annealed films, with the 800-annealed sample showing a relatively well-defined normalized hysteresis response. The optimized device exhibited representative bipolar resistive switching within ±0.5 V, distinguishable high- and low-resistance states, Ohmic conduction in the low-resistance state, and Schottky-emission-dominated transport in the high-resistance state. These results suggest that reversible oxygen-vacancy migration and interfacial barrier modulation govern the switching process. The device showed preliminary synaptic-like transient current responses. Further systematic reliability and conductance-modulation measurements are still required to fully evaluate endurance, reproducibility, and synaptic weight-update behavior. This study demonstrates that annealing-controlled multicomponent ferrite oxides offer a feasible route for energy-efficient memristive synaptic devices.

Magnetochemistry doi: 10.3390/magnetochemistry12070075

Authors: Xiaohan Duan Junkai Zheng Xuebai Guo Yongkui Wang Qianqian Xie Qiuyue Yin Muyao Chen Jingxi Tie

Cr(VI) has become an urgent environmental concern due to its high toxicity. Adsorption is regarded as an effective technique for Cr(VI) removal, and high-performance adsorbents remain in great demand. In this study, waste-derived magnetic biochar (Fe0-Fe3O4 MB) was synthesized via synchronous pyrolysis combined with liquid-phase reduction, using Chinese medicinal residue as biomass feedstock and iron-based sludge as the sole iron source instead of traditional chemical agents. Mössbauer spectroscopy (MS) results confirmed the feasibility and high efficiency of synthesizing Fe0 using iron sludge as the iron source; meanwhile, in situ generated Fe3O4 and biochar effectively restrained particle aggregation and the surface passivation of Fe0. Cr(VI) adsorption fitted well with pseudo-second-order kinetics and Langmuir isotherm models, which suggests a predominant monolayer chemisorption process. The Fe0-Fe3O4 MB possessed excellent superparamagnetism, with a saturation magnetization of 66.74 emu/g. Rapid Cr(VI) adsorption was achieved within 30 min at pH 2 and 35 °C, with a maximum adsorption capacity of 128.36 mg/g. The main adsorption mechanisms may involve multiple pathways, including physical adsorption, electrostatic attraction, chemical reduction, and surface complexation. This study provides a feasible strategy for solid waste resource utilization and the fabrication of stabilized functional zero-valent iron materials, realizing the efficient adsorption treatment of Cr(VI)-containing wastewater.

Magnetochemistry doi: 10.3390/magnetochemistry12070074

Authors: Bin Chen Ge Gao Yuhua Liu Wei Ding Hong Li

Conventional water treatment relies on sequential flocculation and disinfection, which inflates infrastructure costs and heightens the risk of disinfection byproduct formation. Here, we report a magnetic lignin-based flocculant (LS-DMC-AM@Fe3O4) that integrates flocculation, sterilization, and rapid magnetic separation within a single material. The composite was synthesized by thermally initiated graft copolymerization of methacryloyloxyethyl trimethylammonium chloride (DMC) and acrylamide (AM) onto sodium lignosulfonate (LS), followed by incorporation of Fe3O4 nanoparticles (NPs) at 15 wt% loading; the product exhibited a saturation magnetization of 12.8 emu g−1. LS-DMC-AM@Fe3O4 achieved 98.2% kaolin turbidity removal at 1 mg L−1 and 98.6% E. coli removal at 8 mg L−1, and displayed a markedly broader effective dosage window than its non-magnetic analog. We attribute this broadened window to Fe3O4-enhanced membrane disruption, which liberates anionic intracellular contents that buffer excess cationic charge and thereby suppress restabilization. The bactericidal efficiency reached 90% at 18 mg L−1, 1.6-fold higher than LS-DMC-AM, governed by a synergistic dual mechanism: quaternary ammonium contact-killing coupled with Fe3O4 NP-induced intracellular reactive oxygen species (ROS) accumulation. Under an external magnetic field, flocs underwent rapid phase separation and displayed enhanced shear-regrowth capacity (E. coli floc recovery factor: 53% vs. 26%); Fe3O4 NPs were recovered at >95% efficiency over two cycles. Despite higher unit production costs, LS-DMC-AM@Fe3O4 delivers competitive per-unit-volume treatment economics through its ultralow effective dosage and magnetic seed recyclability. These results establish a viable strategy for engineering multifunctional, recyclable flocculants from industrial lignin waste.

Magnetochemistry doi: 10.3390/magnetochemistry12070073

Authors: Mihaela Sofronie Monica Enculescu

Melt-spun Fe70−xPd30Gax ribbons (x = 1 and 3 at.% Ga) were heat-treated at 1223 K for 1 h and 2 h and characterized by X-ray diffraction, scanning electron microscopy, differential scanning calorimetry, magnetometry, and magnetoelastic measurements. Increasing Ga content decreases thermodynamic equilibrium temperature from 292.0 K (1 at.% Ga) to 283.5 K (3 at.% Ga) in as-prepared ribbons. Extended heat treatment then shifts it to 288.0 K and 264.5 K, respectively, and promotes Fe-rich precipitation. Fine precipitates at 1 h preserve a large transformable matrix fraction and introduce microstructural heterogeneity that governs variant mobility and domain-wall pinning; prolonged annealing triggers coalescence, depleting the matrix and reducing both the transformation heat and the magnetoelastic response. Kissinger analysis yields apparent activation energies of 338 kJmol−1 (1 at.% Ga) and 228 kJmol−1 (3 at.% Ga), confirming that higher Ga content lowers the transformation energy barrier. The magnetostrictive response depends on annealing: 1 h-annealed samples exhibit field-induced variant reorientation and saturation magnetostriction of ~60 ppm at 200 K, whereas 2 h-annealed samples approach volume-conserving behavior. Coercivity scales with precipitate density, with Ga3-2h showing anomalously soft magnetic behavior following coalescence. Thermally induced precipitation thus emerges as a route to simultaneously control microstructure, transformation kinetics, magnetoelastic response, and magnetic behavior in ferromagnetic shape memory alloys.

Magnetochemistry doi: 10.3390/magnetochemistry12070072

Authors: Ziqiang Qiao Juan Liu Zhenzhong Wang

With the rapid development of communication technologies, electromagnetic pollution has become increasingly serious, driving the urgent demand for high-performance low-frequency microwave absorbers. This work focuses on Nd-Fe-C powders prepared by high-energy ball milling, aiming to explore low-cost, mass-producible absorbing materials with excellent low-frequency microwave absorption performance. The Nd10.2Fe84.6C5.2 alloy was synthesized via arc melting, and its powders were subsequently fabricated by high-energy ball milling for different milling durations. X-ray diffraction, scanning electron microscopy, and vector network analysis were employed to investigate the effect of high-energy ball milling on the microwave absorption properties of the Nd10.2Fe84.6C5.2 alloy. As the ball milling time increased, the particle size decreased, and the minimum reflection loss shifted to a lower frequency. Additionally, increasing the thickness of the absorbing coating also moved the minimum reflection loss toward the low-frequency region. The Nd10.2Fe84.6C5.2 alloy after 12 h of ball milling had good performance in the C (4.0–8.0 GHz) band when the coating thickness was in the range from 1.4 to 2.2 mm. A minimum reflection loss of −19.2 dB was achieved at 5.2 GHz, and the effective absorption bandwidth (RL < −10 dB, corresponding to a microwave absorption efficiency of 90%) reached 1.8 GHz at a matching thickness of 2.2 mm.

Magnetochemistry doi: 10.3390/magnetochemistry12070071

Authors: Hui Peng Yutong Xie Daode Zhu Longqin Wang Leihao Han Yumeng Cai

Iron powder cores are widely used in cost-sensitive low- to medium-frequency applications because of their high saturation magnetisation, low cost and favourable formability. However, the low electrical resistivity of iron powders favours continuous conductive pathways between adjacent particles, leading to high-frequency eddy-current loss and heat accumulation. To combine electrical insulation, interfacial stability, magnetic-property retention and thermal diffusion in a single coating, a synergistic insulation/thermal-conduction coating based on thiol-functionalised boron nitride was designed for iron-based magnetic powder cores. Hexagonal boron nitride was surface-modified through ultrasonic activation followed by grafting with a mercaptosilane coupling agent, forming covalent linkages on the boron nitride surface. The resulting functionalised nanosheets were deposited onto water-atomised iron powders through interfacial interactions between nitrogen- and sulfur-containing functional groups and the iron surface. A coating content of 5 wt.% produced a relatively continuous and uniform interfacial layer with limited agglomeration, enabling the magnetic powder cores to combine interparticle insulation, loss reduction, magnetic-property retention and thermal transport. The optimised core exhibited a volume resistivity of 58.7 Ω·m and a total core loss of 81.2 kW/m3 at 10 mT and 100 kHz, corresponding to a 20.8% reduction relative to the pure iron core. The sample retained a saturation magnetisation of 201.4 emu/g and an effective permeability of 67.5 at 100 kHz, while achieving a thermal conductivity of 55.2 W/(m·K) and a thermal impedance of 0.215 K·m2/W. Loss-separation analysis indicates that the continuous insulating layer restricts interparticle induced-current pathways and suppresses high-frequency eddy-current loss, while the two-dimensional boron nitride framework promotes internal thermal diffusion.

Magnetochemistry doi: 10.3390/magnetochemistry12070070

Authors: Gayoung Seo Yeon Ju Shin Sangdoo Ahn

Low-field benchtop nuclear magnetic resonance (NMR) spectroscopy has emerged as an accessible analytical platform for rapid, routine, and application-oriented analysis. However, its broader analytical adoption remains constrained by intrinsic limitations, including reduced spectral resolution, severe signal overlap, and lower sensitivity compared with conventional high-field instruments. To address these limitations, artificial intelligence (AI), including machine learning and deep learning approaches, has increasingly been explored alongside conventional chemometric strategies to enhance information extraction from low-field spectral data. This review examines recent developments in AI-assisted benchtop NMR across three major application domains: classification and authentication, quantitative analysis, and spectral processing or automated interpretation. Current evidence suggests that classification and authentication currently represent the most mature application area, whereas quantitative analysis shows promising but often condition-dependent performance. In contrast, spectral reconstruction and automated interpretation remain comparatively early-stage and exploratory, despite their potential long-term relevance for addressing intrinsic information limitations. Key challenges, including limited dataset diversity, poor model transferability, validation pitfalls, limited interpretability, and the lack of benchmarking and standardized workflows, are critically discussed. Future progress will likely depend not only on advances in AI algorithms, but also on the development of robust, reproducible, and analytically meaningful workflows. Overall, AI-assisted benchtop NMR is evolving from proof-of-concept applications toward a more structured analytical framework for extracting chemically meaningful information from spectrally constrained low-field data.

Magnetochemistry doi: 10.3390/magnetochemistry12060069

Authors: Mahmoud AlGharram Tariq AlZoubi Yahia Makableh Jestin Mandumpal

Nickel ferrite (NiFe2O4) is one of the most studied inverse-spinel ferrites because it combines moderate saturation magnetization, comparatively high electrical resistivity, chemical stability, and broad synthesis flexibility. Yet the literature shows that the measured structure and magnetism of NiFe2O4 are not intrinsic constants; they evolve strongly with dimensionality, size, thickness, strain state, cation distribution, surface spin disorder, and synthesis pathway. This review develops a unified theoretical and literature-based interpretation of how dimensionality reshapes the structural and magnetic behavior of NiFe2O4 across bulk ceramics, nanoparticles, one-dimensional nanostructures, polycrystalline thin films, and ultrathin epitaxial films. The review is anchored in the two uploaded nickel ferrite attachments and expanded using internet-sourced journal literature on spinel inversion, surface effects, mechanochemical synthesis, sputtered and pulsed laser deposited thin films, and epitaxial ultrathin-film anomalies. The central novelty of this article is the formulation of a dimensionality-dependent framework in which the observed magnetic response is governed by a competition among three coupled factors: (i) the cation-distribution function, which controls the A–B superexchange balance and therefore the net ferrimagnetic moment; (ii) the microstructural coherence function, which measures how crystallinity, strain, defects, and anti-phase boundaries preserve or degrade exchange continuity; and (iii) the surface/interface spin-order parameter, which quantifies the loss or reconfiguration of magnetic order at free surfaces and buried interfaces. Within this framework, bulk NiFe2O4 behaves as a near-equilibrium inverse spinel with relatively stable magnetization, whereas nanoscale NiFe2O4 experiences strong spin canting and finite-size suppression due to the growing fraction of disordered surface spins. Thin films introduce a distinct regime in which strain, texture, anti-phase boundaries, substrate mismatch, and growth kinetics determine both anisotropy and magnetization. In ultrathin epitaxial films, off-equilibrium cation redistribution and interface-controlled electronic reconstruction may even generate magnetization values far above bulk expectations. The review also compares major synthesis routes—solid-state reaction, sol–gel, co-precipitation, hydrothermal growth, reactive milling, combustion, pulsed laser deposition, and radio-frequency sputtering—and explains why each route biases the final dimensionality-dependent properties differently. A set of word-style equations is provided to formalize spinel inversion, finite-size suppression, anisotropy scaling, coercivity trends, and superparamagnetic crossover. Beyond summarizing the field, the review proposes a regime map linking dimensionality to characteristic structural defects and magnetic signatures, and it identifies unresolved questions concerning the true origin of enhanced magnetization in ultrathin NiFe2O4, the interplay between anti-phase boundaries and strain, and the distinction between intrinsic inversion changes and extrinsic substrate artifacts. The resulting article offers a submission-ready, originality-focused review that positions dimensionality as the master variable governing structure–magnetism correlations in nickel ferrite.

Magnetochemistry doi: 10.3390/magnetochemistry12060068

Authors: Yubing Liu Chenyu Xu Gong Zhang

Understanding the proton relaxation mechanism of hydrogen gas in porous media is critical for underground hydrogen storage. This study investigates the proton relaxation mechanisms of hydrogen gas using variable-pressure NMR experiments on idealized glass bead pack models (6.8–65.9 μm). Results indicate: (1) The proton spin–spin relaxation time (T2) of bulk H2 gas is linearly proportional to pressure, confirming the dominance of the spin–rotation (SR) interaction. (2) In pores larger than 16.4 μm, bulk relaxation prevails, rendering the T2 distribution single-peaked and pore-size independent. (3) Conversely, in 6.8 μm pores, a distinct bimodal T2 distribution emerges, separating free-gas and surface-dominated components. A theoretical critical pore size (≈11.5 μm) was estimated based on a two-phase exchange model. This work elucidates the fundamental regime transition from bulk- to surface-dominated proton relaxation in micron-scale pores.

Magnetochemistry doi: 10.3390/magnetochemistry12060067

Authors: Christian F. Pachl Jonas Braun Christopher E. Anson Karin Fink

Gd(III)-Gd(III) exchange interactions are central to a number of applications, such as the magnetocaloric effect or single molecule magnetism. Broken-symmetry density functional theory is the most widely used computational technique for these calculations, yet no comprehensive benchmark has been established. Here, we present the computational analysis of 27 binuclear Gd(III) compounds in comparison to experimental data and propose a best-practice workflow. We encourage the explicit treatment of scalar relativistic effects and the use of a combination of hybrid functionals with different amounts of exact exchange. Furthermore, we investigated this testbed for structure-property relationships and demonstrated the use of the recommended methodology on two tetranuclear Gd(III) clusters.

Magnetochemistry doi: 10.3390/magnetochemistry12060066

Authors: Mengyu Zhang Liansheng Song Wei Yu Xindi An Shuai Ren Jiongzheng Zhang Shuaida Wang Jiefei Li Junyang Li Ying Li Jianing Li Pan Liao

Magnetically controlled continuum robots (MCRs) emerge as a novel type of flexible robotic system that overcomes the physical limitations of traditional rigid-link structures, exhibiting high compliance, minimal invasiveness, and high spatial freedom. Through non-invasive, precise manipulation using magnetic fields, MCRs can achieve navigation and positioning in complex and confined microenvironments such as blood vessels and cavities in the human body. Furthermore, MCRs have attracted increasing attention for minimally invasive intervention because they combine structural compliance with remote magnetic actuation. In this study, we first introduce the driving control of MCRs, including the driving principle and driving system. Next, we discuss different types of robots, such as guiding and steering robots, variable stiffness robots, multimodal motion robots, and bio-inspired continuum robots, as well as their fabrication materials and manufacturing processes. Subsequently, we analyze the achievements of these robots in the medical field, including cardiovascular treatment, cavity diagnosis and treatment, and bone and joint treatment. The review also discusses current challenges in control accuracy, biocompatibility, system integration, and clinical translation. Finally, we briefly summarize the research and discuss the current challenges and future development directions of MCRs.

Magnetochemistry doi: 10.3390/magnetochemistry12060065

Authors: Fernando Gomes de Souza Carolina de Souza Cardoso Delfino Yuri Ranieri de Medeiros Camargo

This review offers an in-depth look at the diagnostic and therapeutic potential of MNPs as superparamagnetic and high-surface-area-to-volume entities, considering their applications in MRI, magnetic hyperthermia, and targeted drug delivery. Based on an integrative approach, which includes systematic searches in 3 main bibliographic databases, 870 articles, semantic network analysis, Retrieval-Augmented Generation (RAG), and gap classification (Miles’ taxonomy), our analysis identifies a constant gap between lab performances and in vivo applications, described through eight critical challenges. The development of MNP-based biotechnologies is largely hindered by open issues in terms of safety, standardization, and control of the nanobio interface, mainly incomplete physicochemical characterization and poor methodological harmonization, because the high sensitivity of MNPs to synthesis routes and scale is a major bottleneck for GMP-compatible translation. Moreover, the analysis of in vivo data suggests that, on average, less than 1% of the injected dose accumulates in solid tumors, whereas a substantial fraction is diverted to non-target organs, particularly those associated with the mononuclear phagocyte system, reinforcing concerns regarding off-target sequestration, incomplete clearance, and long-term safety. Other critical challenges include complex interactions with biofluids, lack of unifying conceptual frameworks, limited experimental validation, underexploited methodological integration, and geographical and biological biases. Consequently, successfully overcoming these challenges will require the early and deliberate integration of rigorous materials engineering, mechanistic biological insight, and application-oriented validation for robust, reproducible, and translatable magnetic nanoplatforms.

Magnetochemistry doi: 10.3390/magnetochemistry12060064

Authors: Fangjuan Li Yujia Zhao Baoling Ju Xiangli Meng

Magnetic materials have demonstrated considerable potential for applications in the field of energy storage. Spinel-type CoFe2O4 possesses both good redox activity and structural stability, but its magnetism may affect the electrochemical performance. During the high-temperature carbonization and activation processes, the magnetism is significantly weakened, thereby exerting only a limited effect on device performance. To address the issues of high cost and poor environmental friendliness of traditional electrode materials, two types of waste biomass, namely banana peels and sunflower seed shells, were employed as carbon sources for the preparation of Y-doped CoFe2O4/carbon composites in this study. Y-doped CoFe2O4/banana peel carbon was used as the positive electrode, while Y-doped CoFe2O4/sunflower seed shell carbon was used as the negative electrode. The results indicate that the CoFe2O4/BPC cathode doped with 0.4% Y has the best performance, with a specific capacitance of 1788 F/g at 1 A/g and a retention rate of 98% after 10,000 cycles. In addition, the SSPC anode exhibited a specific capacitance of 350 F/g and excellent cycling stability. The assembled device achieved a specific capacitance of 190 F/g at 1 A/g and a capacitance retention rate of 83.6% after 10,000 cycles at 5 A/g, demonstrating good energy density, power density and cycling stability. This research provides experimental evidence for the development of low-cost supercapacitors based on biomass.

Magnetochemistry doi: 10.3390/magnetochemistry12060063

Authors: Jie Zhang Yimin You Kaicai Zhuo Lu Zhu Dongyun Dai Jun Xiao Junxiang Liu Yong Wang

To address the issues of slow operation and high variability in traditional electromagnetic trip devices, this paper proposes a magnetic trip device based on the principle of “permanent magnet holding, spring driving, and electric reset,” thereby reducing the circuit breaker tripping time. However, its high material and manufacturing costs have limited its widespread adoption. To address this issue, this paper employs a method combining orthogonal experiments with BP-NSGA-II. Using permanent magnet dimensions, coil wire gauge, moving component mass, and spring initial force as variables, the number of simulations is reduced through orthogonal experiments, and transient electromagnetic simulation is utilized to analyze the trip mechanism’s dynamic performance; a BP neural network surrogate model was constructed to replace finite element simulation, and the NSGA-II algorithm was employed to perform weightless Pareto optimization, with the volume of the permanent magnet and the amount of copper used in the coil as the cost optimization objectives. Under the constraint of a trip time ≤ 15 ms, the permanent magnet dimensions were reduced from 8 × 44 × 5 mm to 6.5 × 44 × 5 mm (a 18.7% reduction in volume), and the coil wire diameter was optimized from 0.18 mm (2000 turns) to 0.14 mm (1400 turns) (a 22.3% reduction in copper usage). Test results show that the optimized trip time was reduced from 16.0 ms to 14.1 ms, with the prototype measuring 14.56 ms in actual testing; the discrepancy between the simulation and experiment was less than 5%. This method provides a reference for the design of a permanent magnet trip device and holds significant engineering value.

Magnetochemistry doi: 10.3390/magnetochemistry12060062

Authors: Shiyu Zhang Runxian Jiao Lichuan Zhang Qianyu Chen Yuee Xie Yuanping Chen

Van der Waals (vdW) multiferroic tunnel junctions (MFTJs) based on two-dimensional layered materials have emerged as a promising platform for next-generation non-volatile memory devices. In this work, we propose and theoretically investigate a high-performance all-vdW MFTJ consisting of a sliding ferroelectric bilayer GeC barrier sandwiched between asymmetric ferromagnetic metallic electrodes, Fe3GaTe2 and Fe3GeTe2. Using first-principles calculations combined with the non-equilibrium Green’s function (NEGF) method, we demonstrate that the bilayer GeC possesses robust vertical ferroelectricity switchable by interlayer sliding. By incorporating monolayer graphene as protective layers to mitigate metal-induced gap states, the device preserves the intrinsic ferroelectric polarization of the barrier. Our results reveal that four distinct non-volatile resistance states can be realized by independently manipulating the ferroelectric polarization and magnetization configurations. Remarkably, the device exhibits a giant Tunneling Magnetoresistance (TMR) ratio of up to 750.95% and a large Tunneling Electroresistance (TER) ratio of 322.97%. Furthermore, we observe perfect spin-filtering efficiency and a significant negative differential resistance (NDR) effect under finite bias voltage. These findings suggest that the Fe3GaTe2/graphene/bilayer-GeC/graphene/Fe3GeTe2 heterostructure is a compelling candidate for multifunctional spintronic applications in the post-Moore era.

Magnetochemistry doi: 10.3390/magnetochemistry12060061

Authors: Sean Nesbit Monique Harris Md Afzalur Rab Terence Baker Natalia Noginova

Flat and profile-modulated permalloy films have been studied by the electron magnetic resonance (EMR) method. In addition to ferromagnetic and spin-wave resonances, the structures demonstrate low-field EMR signals of an unusual shape, which form a hysteresis loop in sweeping fields. The low-field signals are attributed to a fast reorientation of magnetic domains. The low-field EMR behavior is comparable to the behavior in magneto-dependent photovoltage previously observed in the optical experiments. The shapes of the loops and typical values of the switching fields depend on the profile modulation parameters confirming the possibility of controlling magnetic properties and the coupling of magnetic and optical effects with nanoscale geometry.

Magnetochemistry doi: 10.3390/magnetochemistry12060060

Authors: Xuemei Lin Wei Lin Yunhong Li

In this article, Fe3O4 magnetic particles were prepared via the coprecipitation method, and composite materials (PMCTS) were prepared via a crosslinking reaction of chitosan, polyvinyl alcohol and magnetic particles with glutaraldehydel. The composition, structure, morphology, and magnetic properties of the composite materials were characterized. The effects of the materials input, initial concentration of Pb(II), adsorption time, and temperature on the adsorption performance of PMCTS were further investigated, and the recovery rate of the materials was analyzed. The experiment shows that when the Pb(II) content in water is 30 mg/L, 0.5 g PMCTS are added to the adsorption system, the reaction time is 70 min at 45 °C, and pH = 7, the Pb(II) removal rate can reach 98.9%, and the recovery rate can reach 91.6%. Therefore, PMCTS are fast and effective in adsorbing Pb(II) in water.

Magnetochemistry doi: 10.3390/magnetochemistry12050059

Authors: Sophia I. Klokishner Serghei M. Ostrovsky

A microscopic model has been elaborated for the description of charge transfer-induced spin transitions in crystals containing tetranuclear Fe2Co2 clusters as structural units. The model takes into account the energy spectrum of each Fe2Co2 cluster, formed by the states arising from its initial configuration, two low-spin FeII and two low-spin CoIII, final configuration two low-spin FeIII, and two high-spin CoII, as well as the states that originate from four intermediate configurations of the type of low-spin FeII, low-spin CoIII, low-spin FeIII, and high-spin CoII. Two different types of cooperative interactions are accounted for in the model, namely, the electron–deformational coupling arising as a result of the observed elongation of the cobalt-nitrogen bonds under the low-spin CoIII→ high-spin CoII transition and the interaction via the field of phonons that originates from the coupling of the Co-ions with the full symmetric displacements of the nearest ligand surrounding, which are modulated by crystalline vibrations. The role of cooperative interactions is discussed in detail. Different types of spin transitions are predicted, including the gradual and abrupt ones as well as those manifesting hysteretic behavior. Within the framework of the developed approach, a qualitative and quantitative explanation of the experimental data on the {[(Tp*)Fe(CN)3]2[Co(bpyMe)2]2}(OTf)2·2DMF·H2O compound recently reported oniere is given.

Magnetochemistry doi: 10.3390/magnetochemistry12050058

Authors: Xianwei Jing Ziran Feng Ju Yang Guangming Tian Zhijun Guan

This study systematically investigates the gas–liquid phase transition heat transfer characteristics and volatilization loss behavior of magnetic liquid sealing devices under high-temperature and high-speed operating conditions. A magneto-thermal flow-coupled numerical model was established using ANSYS Maxwell (2025 R1) and Fluent (2025 R1) software to simulate and analyze the influence of rotational speed, solid content, and shaft diameter on the temperature distribution and gas-phase evolution of the magnetic liquid within the sealing gap. An experimental platform was also constructed for validation. The research indicates that increasing rotational speed significantly intensifies the vaporization of magnetic liquid, with bubbles migrating towards lower-concentration regions. The influence weight of rotational speed on phase transition is greater than that of shaft diameter. Under identical temperature fields, the phase transition interface morphology and the proportion of gas–liquid two-phase regions among magnetic liquids with different solid contents are highly similar. However, high-solid-content magnetic liquid can inhibit phase transition due to dense particle packing. Increasing shaft diameter notably expands the vaporization region, easily forming through-leakage channels.

Magnetochemistry doi: 10.3390/magnetochemistry12050057

Authors: Chijiawen Fang Jie Zhang Jianwei Zheng Dongsheng Shi Wenjin Wu Jingwu Zheng Liang Qiao Wei Cai Yao Ying Juan Li Jing Yu Akihisa Inoue Shenglei Che

Annealing is a critical step in the fabrication of soft magnetic composites (SMCs), and precise coordination of annealing atmosphere and temperature is essential for optimizing their performance. In this study, FeSiCr SMCs were annealed under three different atmospheres (air, nitrogen, and argon) across a range of temperatures, and the effects of the annealing atmosphere on their microstructure and soft magnetic properties were systematically investigated. The results demonstrate that annealing in an inert atmosphere, particularly argon, within the temperature range of 450–750 °C, yields superior magnetic properties compared with air annealing. After annealing under argon at 550 °C, the effective magnetic permeability (μe) reached 47.5, and the power loss (Pcv) was 1457.3 kW/m3 at 1000 kHz and 30 mT. These improvements are primarily attributed to effective stress relaxation and the substantial retention of the polyvinyl butyral (PVB) insulating layer. With further increases in annealing temperature, the magnetic properties deteriorate rapidly due to the complete decomposition of PVB and the formation of conductive chromium carbides. Under such conditions, air annealing exhibits distinct advantages. Selective oxidation of FeSiCr occurs, leading to the formation of a dense chromium oxide insulating layer that enhances magnetic performance (after annealing at 850 °C, μe = 47.9, Pcv = 1632.0 kW/m3). Moreover, the mechanical properties were significantly improved, with the radial crush strength increasing from 22.36 N in the unannealed state to 330 N after annealing. These results indicate that the comprehensive performance of SMCs can be effectively tailored through the appropriate selection of annealing atmosphere and temperature, providing valuable guidance for the design and optimization of high-performance SMCs.

Magnetochemistry doi: 10.3390/magnetochemistry12050056

Authors: Pikesh Pal Iurii Kibalin Arsen Goukassov Thomas C. Hansen Eddy Lelièvre-Berna Yann Garcia Grégory Chaboussant

[MnIII(pyrol)3(tren)] {(Hpyrol)3tren = tris(1-(2-azolyl)-2-azabuten-4-yl)amine)} is a mononuclear spin-transition compound switching between high spin (HS, S = 2) and low spin (LS, effective S = 1) around 47 K, preserving I4¯3d symmetry. Its magnetic anisotropy is studied by calculating the atomic susceptibility tensor from the refinement of polarized neutron powder diffraction. The analysis reveals that the weakly prolate-type atomic magnetic anisotropy in the HS state abruptly switches to uniaxial needle-shaped/Ising-type anisotropy in the LS state. However, the overall magnetic anisotropy of the unit cell remains isotropic due to the cubic nature of the crystal symmetry. Irreversible coexistence of mixed spin states HS/LS is observed in the vicinity of the cooperative spin crossover, where the average magnetic moment of Mn3+ shows a hysteretic temperature variation. This hysteretic mixing of HS and LS at intermediate temperatures suggests complex growth and nucleation of HS and LS domains. The study demonstrates that polarized powder neutron diffraction is a unique and powerful tool for describing complex magnetic anisotropies and magneto-structural correlations in molecular-based magnetic materials.

Magnetochemistry doi: 10.3390/magnetochemistry12050055

Authors: Cătălin-Daniel Constantinescu Eros-Alexandru Pătroi Nicu-Doinel Scărișoreanu Antoniu-Nicolae Moldovan Anca-Gabriela Nedelcea Cătălin-Romeo Luculescu Cosmin Cobianu Maria-Cătălina Petrescu Lucian-Gabriel Petrescu

Cobalt/copper (Co/Cu) multilayers are prototypical systems for giant magnetoresistance (GMR)-based spintronic devices, where interfacial quality and spin-dependent scattering critically determine performance. In this work, Co/Cu multilayers were fabricated by pulsed laser deposition (PLD) on SITAL ceramics, Si(100), and BK7 substrates, with 10, 20, and 40 bilayer repetitions, in order to elucidate the interplay between microstructure, interfacial diffusion, and magnetotransport properties. Systematic characterization combining atomic force microscopy (AFM), scanning electron microscopy (SEM), SIMS/SNMS depth profiling, vibrating sample magnetometry (VSM), and Hall effect measurements reveals that PLD enables controlled multilayer growth with low background roughness and well-defined periodic structures, despite the presence of characteristic particulates. A clear dependence of the GMR response on both bilayer number and substrate type is observed. Increasing the number of repetitions enhances spin-dependent scattering at Co/Cu interfaces, leading to a progressive increase in the magnetoresistance amplitude, reaching ~−14% for 40-period multilayers on SITAL substrates. This enhancement is attributed to the higher interface density and improved interfacial coherence, as confirmed by SIMS/SNMS analysis showing reduced interdiffusion in thicker stacks. In parallel, Hall effect measurements indicate a reduction in carrier density and an increase in carrier mobility with increasing multilayer thickness, consistent with improved charge transport stability. A pronounced substrate effect is demonstrated: SITAL-supported multilayers exhibit enhanced GMR sensitivity (up to ~44%·T−1) due to increased diffuse spin-dependent scattering at rougher interfaces, whereas Si(100) substrates promote smoother growth, improved structural coherence, and more stable electronic transport. While sputtering typically enables smoother interfaces and higher GMR ratios, PLD offers enhanced flexibility in tailoring interfacial morphology and diffusion processes, which can lead to improved sensitivity under specific conditions. These results establish PLD as a versatile route for tailoring Co/Cu multilayers, enabling controlled optimization of the trade-off between sensitivity and structural quality for advanced spin-valve and magnetic sensor applications.

Magnetochemistry doi: 10.3390/magnetochemistry12050053

Authors: Jue Hou Lirong Dou Lun Zhao Yepeng Yang Xing Zeng Tianyu Zheng

Pore-throat structures in a carbonate reservoir were classified into ten petrophysical facies representing coarse, medium, or fine throat types based on Mercury Injection Capillary Pressure (MICP) data from 77 core samples, directly reflecting distinct flow capacities. Using Nuclear Magnetic Resonance (NMR) data from 20 samples, an artificial neural network (ANN) model was developed with four conventional logs, namely Gamma Ray (GR), Deep Laterolog Resistivity (RD), Density (DEN), and Compensated Neutron Log (CNL), as inputs to predict the T2 spectrum continuously. A cumulative pore-throat size distribution matching method was then used to transform predicted T2 spectra into capillary pressure curves. The resulting pore-throat parameters show excellent agreement with core measurements, with relative errors for key parameters—such as median pore-throat radius (R50) and sorting coefficient (Sp)—below 15%. This approach extends discrete core data to continuous wellbore profiles, enabling pore-throat prediction and facies classification in intervals lacking MICP data. It effectively identifies dominant flow channels and tight interlayers, with facies validated by thin-section petrography, providing a robust basis for evaluating highly heterogeneous carbonate reservoirs.

Magnetochemistry doi: 10.3390/magnetochemistry12050054

Authors: Xiulan Zhu Yanju Li Chaoqun Ren Zhanjun Chen Tai Xu Anzhao Ji Changrui Kou

The microscopic pore structure and fluid occurrence laws of tight oil reservoirs are intricate, leading to relatively low oil production rates. The T1-T2 two-dimensional nuclear magnetic resonance (2D NMR) technique presents significant advantages for fluid identification and the quantitative characterization of fluids and pore spaces in these reservoirs. Nonetheless, systematic and in-depth investigations into its experimental measurements remain scarce. A comprehensive review of both domestic and international literature on T1-T2 2D NMR measurement techniques was conducted for oil reservoirs. The fundamental principles, data acquisition and inversion mechanisms of 2D NMR technology were elucidated. Additionally, the signal distribution laws of hydrogen-containing components under varying test parameters were summarized. The relationship between NMR experimental testing and reservoir characteristics was explored, elucidating the mechanism of the T1-T2 spectra. Building upon this foundation, the strategic optimization of data acquisition and inversion methodologies, along with critical parameters for T1-T2 NMR measurements, significantly enhanced the precision of NMR datasets and the fidelity of 2D NMR spectral imaging. These advancements provide a theoretical basis and technical support for the characterization of rock and fluid in tight oil reservoirs.

Magnetochemistry doi: 10.3390/magnetochemistry12050052

Authors: Zhimin Sun Feng Ren Lan Mei Jing Wang Yuan Cheng

Polyalphaolefin (PAO)-based magnetic fluids are widely used in precision transmission systems for their excellent rheological and lubricating properties, but their stability and magnetic controllability under high-temperature and high-shear conditions remain a key challenge. In this work, a PAO2-based magnetic fluid was prepared via coprecipitation using a sequential modification strategy involving oleic acid and alkenyl succinimide. An energy competition model under multi-field coupling was established using the magnetothermal energy ratio (λ) and Mason number (Mn) to elucidate the system’s rheological behavior. The fluid shows significant shear-thinning behavior under zero magnetic field; a 60 kA/m magnetic field increases the relative viscosity by over 4 times at 5 s−1, while the magnetoviscous effect becomes weak at shear rates over 500 s−1 (corresponding approximately to Mn = 1). With increasing temperature, the field-induced viscosity enhancement decreases progressively as thermal disturbance becomes increasingly important. This work reveals the multi-field coupling rheological mechanism, and the results suggest that the OA/T154 modification strategy is a feasible route for obtaining a PAO-based magnetic fluid that remains dispersible and magnetically responsive under the tested conditions. The study provides theoretical and experimental support for the design of intelligent lubricating materials.

Magnetochemistry doi: 10.3390/magnetochemistry12050051

Authors: Coriolan Tiușan Roxana Dudric Maria Căpățînă Radu George Hațegan Romulus Tetean

The structural and magnetic properties and band structure results of HoCo3−xSix compounds are reported. First-principles GGA+U+SO calculations, compared with magnetometry experiments, provide deep insight on the magnetic properties of the HoCo3 compound. They show that HoCo3 is a robust ferrimagnet, with strongly localized Ho-4f moments in excellent agreement with neutron data and itinerant Co-3d magnetism, where inclusion of the interstitial contribution brings the Co moments into very good agreement with the experimental data. The electronic structure reveals sharp Ho-4f states well below EF, exchange-split Co-3d bands crossing EF, and noticeable Ho-5d–Co-3d hybridization that mediates the antiparallel Ho–Co coupling and explains the non-negligible interstitial moment, providing a consistent microscopic picture that supports the experimentally observed increase in magnetization upon Co-Si substitution. Metamagnetic transitions are shown in magnetization isotherms. The observed transitions are broad and can be explained by the distribution of internal magnetic fields which arises from differences in the local environments of cobalt atoms. The magnetic properties were correlated with the theoretical results. Two transitions were revealed below room temperature, one due to a transition to a noncollinear magnetic structure and the other due to a temperature-induced metamagnetic transition.

Magnetochemistry doi: 10.3390/magnetochemistry12050050

Authors: Xinwei Shi Zhichao Geng Yanfeng Sheng

Hydrogen (H2) storage in subsurface formations has recently gained attention as a promising large-scale energy storage solution. Although previous studies have revealed distinct displacement behaviors between H2 and other gases such as nitrogen (N2) and carbon dioxide (CO2) in high-permeability sandstones, the mechanisms governing H2 migration in tight formations remain largely unexplored. To provide experimental observations that may help improve the understanding of H2 migration in tight reservoirs, we conducted H2 flooding experiments on a tight sandstone sample from the Ordos Basin under pore fluid pressures of 0.5, 1, and 2 MPa. Dynamic core flooding processes were monitored using a low-field nuclear magnetic resonance (NMR) analysis system. The capillary number (Nc) in this work ranged from 1.7 × 10−9 to 3.4 × 10−9, indicating a capillarity-dominated flow. H2 saturation in the tight sandstone increased from 41.9% to 53.3% and then to 57.7% with increasing pore fluid pressure. Under a pore fluid pressure of 0.5 MPa, H2 initially displaced water in small pores (T2 < 10.5 ms), leading to prolonged fluctuations in water content over 136 min before significant displacement occurred in large pores (10.5 ms < T2 < 6579.3 ms). In contrast, at a pore fluid pressure of 2 MPa, the water in large pores was more significantly impacted, with a marked decrease in water saturation observed after 8 min of flooding. These findings provide direct experimental evidence of pressure-dependent and pore-scale selective displacement patterns of H2 in tight sandstone, offering new insights into the fluid dynamics that control hydrogen injectivity and storage efficiency in low-permeability reservoirs.

Magnetochemistry doi: 10.3390/magnetochemistry12040049

Authors: Milena A. Pereira Larissa P. N. M. Pinto Hélio F. Dos Santos Diego F. S. Paschoal

Platinum chemistry covers a wide range of applications, including homogeneous and heterogeneous catalysis as well as cancer therapy. Numerous Pt complexes have been synthesized and studied in recent years, with NMR spectroscopy serving as the primary technique for structural characterization. The 195Pt nucleus has favorable features for NMR studies, being highly sensitive to ligand type and structural environment. From a computational perspective, factors such as solvent effects, relativistic corrections, and the electronic structure of the ligands strongly influence the calculated NMR parameters. Consequently, establishing a general computational protocol for 195Pt NMR prediction remains a challenging task. In this work, we present a systematic validation and extension of our previously developed computational protocol, originally proposed for Pt(II) complexes, in studying 195Pt NMR chemical shifts in Pt(II)-Sn(II) complexes. A benchmark set of 100 Pt(II)-Sn(II) complexes was analyzed, yielding good agreement with experimental data (R2 = 0.86, MRD = 3.6%, MAD = 163 ppm), which is remarkable given the structural diversity and broad range of chemical shifts covered.

Magnetochemistry doi: 10.3390/magnetochemistry12040048

Authors: Jesús Alexis Salcedo Muciño Juan Alejandro Flores Campos Adolfo Angel Casares Duran Juan Carlos Paredes Rojas José Juan Mojica Martínez Christopher René Torres-SanMiguel

In this article, the motion control of ferromagnetic particles through varying a non-invasive magnetic field is addressed. Within an experimental test bench, three experiments are proposed to verify motion control, which consist of control of the distance between electromagnets, retention of particles over the flow, and manipulation of the direction of particle flow at a “Y”-type bifurcation emulating an “OR” gate. At each experimental stage, instrumented test benches were integrated with current, distance, and flow sensors, enabling measurement and feedback of the system’s physical variables. These benches were configured using pulse-width-modulation (PWM) and Proportional–Integral–Derivative (PID) controllers to regulate the current supplied to the electromagnets and, thereby, control the intensity of the induced electromagnetic field according to the requirements of each experiment. Different study cases were defined to analyze the operational limits of the system by varying the current influencing the electromagnetic field and the configuration of the electromagnets. The results describe the response of the magnetic field, the induced force, and the behavior of the suspended particles under each condition, providing elements to characterize the performance of the electromagnetic system in operational scenarios and contributing to the understanding of the phenomena associated with the non-invasive manipulation of ferromagnetic particles by means of controlled magnetic fields.

Magnetochemistry doi: 10.3390/magnetochemistry12040047

Authors: Ahmad M. Alsaad

The study presents a comprehensive first-principles investigation of the structural, electronic, and magnetic properties of rocksalt scandium nitride (ScN) and its Cr- and Mn-doped derivatives using spin-polarized density-functional theory within the GGA + U (UCr = 3.5 eV, UMn = 2.7 eV) and HSE06 frameworks. Pristine ScN crystallizes in the cubic Fm3–m structure and exhibits narrow-gap semiconducting behavior, with an indirect band gap of 0.82 eV obtained from hybrid-functional calculations, in excellent agreement with reported theoretical values. Substitutional doping with Cr and Mn introduces localized 3d states near the Fermi level, driving a transition toward spin-polarized metallic or half-metallic behavior accompanied by robust ferromagnetism. Density-of-states and band-structure analyses reveal that magnetism and charge transport in the doped systems are dominated by exchange-split transition-metal 3d states hybridized with N-2p orbitals. Total energy calculations confirm ferromagnetic ground states for both Cr- and Mn-doped ScN, with Mn substitution yielding stronger exchange stabilization and higher magnetic moments. Magnetocrystalline anisotropy energies, evaluated using the force-theorem approach, are found to be negligibly small, indicating weak anisotropy consistent with the moderate spin–orbit coupling strength in ScN-based nitrides. Nevertheless, symmetry breaking around dopant sites gives rise to a finite Dzyaloshinskii–Moriya interaction, leading to weak spin canting and non-collinear magnetic tendencies. The interplay between magnetic exchange coupling, spin–orbit interaction, and local inversion symmetry breaking positions of Cr- and Mn-doped ScN as promising dilute magnetic semiconductors with tunable spin polarization and chiral magnetic interactions, offering a viable platform for nitride-based spintronic and magneto-electronic applications.

Magnetochemistry doi: 10.3390/magnetochemistry12040046

Authors: Zhuoqian Xie Chenjun Xu Yunye Shi Nanxi Lin Qisheng Tu

Birefringence, arising from the low-symmetry structure in orthorhombic LaFeO3, limits the observation and utilization of magneto-optical effects. In this study, the pure-phase perovskite-typed La1−xCexFe1−xTixO3/SiO2 thin films were successfully fabricated via radio-frequency magnetron sputtering, where the co-doping of Ce3+ and Ti4+ ions effectively induced a structure transition from orthorhombic to a highly symmetric cubic phase, eliminating birefringence effect and thus reducing optical transmission loss. At the same time, the doped Ce3+ ions also effectively enhanced the magnetic and magneto-optical effects of the system due to their strong spin coupling effect and superexchange interaction with Fe3+ ions. The results show that the cubic-phase La0.5Ce0.5Fe0.5Ti0.5O3/SiO2 thin film exhibits excellent magnetic and magneto-optical performance. Their saturation magnetization reaches 180 emu/cm3 with an in-plane easy magnetic axis. And their magnetic circular dichroic ellipticity |ψF| reaches 3054 degrees/cm.

Magnetochemistry doi: 10.3390/magnetochemistry12040045

Authors: Yan-Fang Wu Zheng Huang Jing Wei Rong-Jie Hao Jia-Ying Wang Yan Peng Ning Song Zhao-Bo Hu Yu-Hui Tan Yun-Zhi Tang

Electronics evolution drives SMMs as a frontier, overcoming conventional magnetic material limits via molecular spin coupling. Two relevant Co(II) mononuclear complexes, [Co(MOP)4(N3)2] (1) and [Co(MSP)4(N3)2] (2) (MOP = 4-methoxypridine and MSP = 4-methylthiopyridine) were synthesized through changing the substituents of ligands. The Co(II) ions in the two complexes show octahedron coordination geometries. The replacement of the O to S in the equatorial plane leads to different Jahn–Teller effect because of the shorter Co(II)-N in the equatorial plane, resulting in the significantly different slow relaxation process confirmed by ab initio calculation. The results confirm the Co(II) ion is sensitive to ligand field.

Magnetochemistry doi: 10.3390/magnetochemistry12040043

Authors: Qilong Wu Zhuo Sun Anjian Pan Huidong Qian Yixing Li Jinkui Fan Jiantao Feng Lizhong Zhao Zhongwu Liu Xuefeng Zhang

Enhancing grain orientation along the <001> crystal axis in AlNiCo alloys is crucial for developing high-performance permanent magnets. Traditional directional solidification, known as the “cold plate-hot mold” method, is constrained by a low thermal gradient, leading to inadequate microstructural uniformity and crystallographic alignment, which impedes the optimization of magnetic properties. In this study, we employed a high-speed solidification process with an enhanced cooling gradient to fabricate AlNiCo magnets at various withdrawal rates. The variation in drawing rate influenced grain orientation within the alloy, thereby altering the degree of alignment of the ferromagnetic α1 phase following subsequent heat treatment, which ultimately affected the magnetic properties. The optimal magnetic performance was attained at a withdrawal rate of 50 μm/s, where the sample exhibited the most favorable oriented microstructure, with a remanence (Br) of 10.62 kGs, intrinsic coercivity (Hcj) of 1.794 kOe, and a maximum energy product (BH)max of 10.93 MGOe. Moreover, magnets at different positions exhibit excellent consistency in magnetic properties, enhancing the material utilization efficiency. This research provides valuable process parameters and a foundational basis for developing high-performance AlNiCo alloys.

Magnetochemistry doi: 10.3390/magnetochemistry12040044

Authors: Linli Wang Yongchun Liang Feng Huang Yingchao Yue Xiaoyu Luo

In order to conduct a systematic study on the influence of the copper element on the soft magnetic properties of alloys, a series of alloy ribbons with compositions of Fe90.70−xGd2.32B6.98Cux (x = 0.25, 0.5, 0.75, 1.0, 1.25, and 1.5) were fabricated via the single-roller melt-spinning method. The microstructure and magnetic properties of these ribbons were systematically characterized using X-ray diffraction (XRD), differential scanning calorimetry (DSC), and vibrating sample magnetometry (VSM). The research findings indicate that the introduction of the copper element significantly enhances the soft magnetic properties of the alloys. For the alloy ribbon with the optimized composition of Fe89.95Gd3.32B6.98Cu0.75, the saturation magnetization (Bs) attains 1.74 T. The improvement in performance is primarily attributed to the precipitation of the nanocrystalline α-Fe phase. This phase features fine grain sizes and relatively wide magnetic domain structures, which contribute to an increase in the saturation magnetization and a reduction in the coercivity, thus comprehensively optimizing the soft magnetic properties of the alloys.

Magnetochemistry doi: 10.3390/magnetochemistry12040042

Authors: Jiahao Dong Hao Lu Zhenfei Shen Zhenkun Li

Magnetic fluid sealing is an ideal solution for high-end equipment. However, traditional rectangular pole teeth suffer from low magnetic flux utilization and insufficient pressure resistance. Meanwhile, the pressure transmission mechanism of different pole teeth and the evolution law of magnetic fluid boundary morphology remain unclear, restricting structural optimization. This study investigates rectangular and trapezoidal pole teeth by adopting the Volume of Fluid model, combined with finite element simulation and experimental verification. A sealing simulation model and a dedicated experimental platform were established to systematically explore the effects of the two pole tooth types on pressure transmission efficiency and magnetic fluid boundary morphology under static and dynamic sealing conditions, as well as their pressure resistance and self-recovery characteristics. Results show that trapezoidal pole teeth exhibit superior pressure resistance to rectangular ones due to optimized magnetic field distribution: the maximum static sealing pressure resistance increases by 40.9 kPa, and the dynamic sealing pressure resistance at 8000 rpm rises by 63.2 kPa. The 2% deviation between simulation and experimental data verifies the model’s reliability. This work clarifies the intrinsic relationship between pole tooth structure and sealing performance, reveals the pressure transmission mechanism of different pole teeth, and provides theoretical and engineering references for pole tooth structural optimization, which is significant for improving the pressure resistance stability and engineering applicability of magnetic fluid sealing.

Magnetochemistry doi: 10.3390/magnetochemistry12040041

Authors: Andreas Kaidatzis María Garrido-Segovia José Miguel García-Martín Nikolaos C. Diamantopoulos Dimitrios-Panagiotis Theodoropoulos Panagiotis Poulopoulos

Composite ZnO/Fe nanostructured thin films are synthesized via physical vapor deposition using radio frequency magnetron sputtering in conventional, as well as in glancing angle deposition (GLAD) geometries. ZnO is employed as a compact nanocolumnar template to direct Fe growth in bilayer and multilayer architectures. Morphological analysis reveals well-defined ZnO/Fe interfaces for normal deposition geometry, with diminished interface clarity and reduced layer thickness in GLAD samples. Crystallographic characterization indicates clear ZnO-{002} and α-Fe-{110} texture. Magnetostatic characterization investigates the effects of morphology on coercivity and domain nucleation. GLAD-deposited Fe films exhibit clear in-plane magnetic anisotropy, with remanence to saturation magnetization (MREM/MSAT) equal to 1 for the easy axis and equal to 0.24 for the hard axis, consistent with inclined nanocolumn morphology. Our findings show that deposition geometry, rather the ZnO template, mostly affects the morphology of Fe films. The above, highlight the potential of engineered ZnO/Fe nanocomposites for magnetic, spintronic, and magnetoplasmonic applications, by tuning morphology and interface quality through deposition parameters.

Magnetochemistry doi: 10.3390/magnetochemistry12040040

Authors: Sandor I. Bernad Elena S. Bernad

Magnetic drug targeting (MDT) is commonly evaluated by peak accumulation at the target site. Under pulsatile flow, however, initial deposition does not predict sustained localisation. We introduce the Magnetic Targeting Optimisation Concept (M-TOC), a safety-constrained framework that restructures MDT evaluation by separating geometric deposition from retention stability and embedding both within a defined hemodynamic safety window. Deposition (D) was quantified by using obstruction degree at the injection end, OD(T0), and restricted by a structural admissibility limit (OD_max = 40%). Retention stability (R) was quantified using early washout at T0 + 30 s and an apparent half-life (τ1/2) derived from coverage decay under controlled pulsatile washout. These descriptors were integrated into a Unified Targeting Score (UTS), applied only within the admissible domain, thereby enforcing feasibility before optimisation. Three PEG-functionalised magnetoresponsive nanocluster formulations were evaluated under identical magnetic and flow conditions. D–R mapping identified distinct operating regimes and showed that no tested configuration simultaneously achieved admissible deposition and robust pulsatile stability. By formalising MDT as a constrained multi-objective problem, M-TOC provides an objective method for regime discrimination and a transferable design principle for stability-guided targeting under physiological flow.

Magnetochemistry doi: 10.3390/magnetochemistry12040039

Authors: Mao Liao Zhenggui Li Zhaoqiang Yan Chuanjun Han Wei Tai Xin Chen Yu Zheng

This study focuses on the reliability issue of magnetic fluid (MF) in the magnetic fluid sealing technology for the upper guide bearing (UGB) of hydro-generators and proposes selection schemes for MF suitable for different models of hydro-generators. By analyzing the performance indicators of five base fluids and MFs, including the acid value, flash point, oxidation stability, magnetorheological performance, breakdown voltage, dielectric loss factor and volume resistivity, the influencing factors of the insulating performance of MFs and their mechanism in sealing the UGBs of hydro-generators are investigated. The results show that, when the spindle speed is below 27 rpm, the viscosity of the MF is dominated by the magnetic field strength, while, when the speed exceeds 27 rpm, the viscosity of the MF is dominated by the shear rate. In addition, the addition of magnetic nanoparticles (MNPs) causes the breakdown voltage of the base carrier liquid to fluctuate in the range of 31.2–55.9 kV, the dielectric loss factor to fluctuate in the range of 2.5 × 10−4–6.7 × 10−3, and the volume resistivity to fluctuate in the range of 2.8 × 1011–2.6 × 1012 Ω·m. The research results provide a theoretical basis for the application of high-efficiency and stable magnetic fluid sealing technology.

Magnetochemistry doi: 10.3390/magnetochemistry12030038

Authors: Siyu Wei Gang Gui Cancan Yuan Ziqi Fan Qin Xu

Background: Co-delivery of two drugs with diverse physicochemical properties and a specific administration sequence holds great importance in cancer theranostics to overcome drug resistance and reduce side effects. Paclitaxel (PTX) and hydroxycamptothecin (HCPT) have long been used clinically as chemotherapeutic agents for Nasopharyn-geal carcinoma (NPC). However, their clinical application is severely restricted by low water solubility, poor stability, and systemic adverse reactions. Nanoparticle-based drug delivery systems provide a promising platform for combination cancer therapy. Methods: In this study, folic acid-modified and dual drug-loaded self-assembled HCPT/PTX@FA@p-PS-SPIONs were successfully fabricated via the emulsification–solvent evaporation method using amphiphilic phosphorylated polystyrene (p-PS). The characterization, cellular uptake, and in vivo pharmacokinetic profiles of the nanoparticles in NPC models were systematically investigated. Result: HCPT/PTX@FA@p-PS-SPIONs were successfully prepared with p-PS as the copolymer backbone. The nanoparticles exhibited a uniform particle size of 196.9 ± 5.5 nm and a zeta potential of −7.3 ± 0.7 mV. The encapsulation efficiency (EE) was 81.4 ± 2.5% for PTX and 67.6 ± 4.1% for HCPT. The drug loading (DL) efficiency was 18.4 ± 1.5% for PTX and 12.2 ± 1.0% for HCPT. HCPT/PTX@FA@p-PS-SPIONs showed favorable biocompatibility. Sustained and sequential release of the two drugs contributed to an enhanced therapeutic effect. Moreover, under magnetic field (MF) guidance, HCPT/PTX@FA@p-PS-SPIONs exhibited stronger inhibitory effects on NPC cells than single-drug, cocktail, or dual-drug groups, demonstrating the superiority of the combined therapy. Pharmacokinetic studies in rats revealed that the half-lives of PTX and HCPT were 3.9 ± 1.2 h and 4.7 ± 1.1 h, respectively, confirming that HCPT/PTX@FA@p-PS-SPIONs could resist rapid metabolism and clearance in vivo. Conclusions: The long-circulating, folic acid-targeted nanoparticles HCPT/PTX@FA@p-PS-SPIONs show great potential for the targeted therapy of nasopharyngeal carcinoma.

Magnetochemistry doi: 10.3390/magnetochemistry12030037

Authors: Tiancai Zhang Yi Yang Tao Hong

MXene-based microwave absorbers have received extensive attention owing to their high electrical conductivity, abundant interfacial polarization sites, and tunable surface terminations. However, the structure–property relationship of MXene composites remains highly nonlinear, and the design of high-efficiency absorbers still relies heavily on trial-and-error experiments. Herein, multidimensional magnetic components, including zero-dimensional (0D) Fe3O4 nanoparticles, one-dimensional (1D) Fe3O4/Co3O4 nanowires, and two-dimensional (2D) Fe3O4-based heterostructures, were rationally integrated with Fe/MXene and Fe/Co/MXene nanosheets to engineer synergistic dielectric and magnetic losses. Comprehensive electromagnetic characterization and loss mechanism analysis reveal that the structural dimensionality strongly impacts impedance matching and attenuation capability. To further enable predictive and data-driven optimization, a machine learning framework was established to correlate the microstructure, component ratio, thickness, and electromagnetic parameters with the microwave absorption performance (e.g., minimum reflection loss (RLmin), effective absorption bandwidth (EAB)). The optimized multidimensional composite achieves an RLmin of −56.4 dB at 10.2 GHz with an EAB of 8.4 GHz (9.6–18.0 GHz) at a thin matching thickness of 1.8 mm. The machine learning model demonstrates excellent accuracy (R2 = 0.947) and enables the inverse design of absorber geometries to target specific operational frequencies. This work provides a generalizable paradigm for the intelligent design of MXene-based microwave absorbers and opens up broader opportunities for the AI-accelerated discovery of advanced electromagnetic functional materials.

Magnetochemistry doi: 10.3390/magnetochemistry12030036

Authors: Sajjad Ur Rehman Zhitao Wang Ronghai Yu Qiulan Tan Munan Yang

This manuscript reports the influence of Hf substitution for Fe on the magnetic properties and microstructure of near-stoichiometric Pr-Fe-B alloys. Melt-spun ribbons with nominal compositions of Pr26.7Fe72.3B1, Pr26.7Fe71.8Hf0.5B1, and Pr26.7Fe71.3Hf1B1 (wt%) are synthesized with optimized wheel speed. Transmission electron microscopy analysis reveals that Hf addition effectively refines the grain structure in terms of grain size. Magnetic characterization at 300 K demonstrates that the partial Hf addition significantly enhances the hard magnetic performance. The pristine alloy (Pr26.7Fe72.3B1) exhibits an intrinsic coercivity (Hcj) of 11.95 kOe, a remanence (Br) of 8.23 kG, and a maximum energy product ((BH)max) of 12.6 MGOe. With 0.5% Hf addition, the properties improve to Hcj of 11.47 kOe, Br of 8.5 kG, and (BH)max of 15.33 MGOe. A further increase to 1.0% Hf leads to a slight reduction in properties, with Hcj of 11.66 kOe, Br of 8.37 kG, and (BH)max of 13.32 MGOe, though they remain superior to the pristine alloy. Furthermore, Hf addition improves the high-temperature magnetic stability. The results indicate that optimal Hf addition is a promising strategy for enhancing the magnetic properties of near-stoichiometric Pr-Fe-B ribbons through microstructural refinement and reducing the volume fraction of the soft magnetic phase.

Magnetochemistry doi: 10.3390/magnetochemistry12030035

Authors: Razvan Hirian Roxana Dudric Rareș Bortnic Florin Popa Lucian Barbu-Tudoran Teodora Radu Fran Nekvapil Ioan Botiz Raluca Lucacel-Ciceo

In this work, La0.70Ca0.25Sr0.05MnO3 perovskite nanoparticles were produced in large amounts (in a single batch) and were embedded into filaments for 3D printing alongside carbon fibers. The produced materials showed room-temperature magnetocaloric effects proportional to the quantity of encapsulated nanoparticles. Moreover, the thermal properties of 3D-printed pellets (produced using the composite filaments) were also analyzed and compared to standard filaments.

Magnetochemistry doi: 10.3390/magnetochemistry12030034

Authors: Jiawen Zhang Chisen Qin Nan Liu Zheng Lian Guangwen Sun Bin Liu Lijian Yang

A hard spot defect refers to structural defects that occur in long-distance oil and gas pipelines during the thermal processes. These defects arise from the combination of material phase changes and stress concentration, making them challenging to detect. Weak magnetic detection technology is an effective approach for identifying microscopic phase transformations and stress concentrations in materials. This study develops an ontological model linking hardness, stress, and magnetic signals at hard spots, and both simulations and real experiments are conducted to validate the model. The findings indicate a strong correlation between the model and experimental observations. The research also examined how hardness and defect shape influence magnetic signals and revealed that both the tangential and normal components of the weak magnetic signal at hard spots increase with higher hardness levels. Additionally, the peak value of the defect rises with an increasing depth-to-width ratio, and the difference between the center and peak values grows. According to the linear variation in the current constitutive model, the magnetic signal amplitude increases by approximately 35% for every 0.8% rise in hardness, with growth rates of 0.23% and 0.26% for the amplitude at the center and peak endpoint of the tangential magnetic signal, respectively. The hard spot shape parameter, Hd, is derived from the spacing of the tangential and normal peak-to-peak values, which indicates the size of the hard spot and increases consistently with the depth-to-radius ratio.

Magnetochemistry doi: 10.3390/magnetochemistry12030033

Authors: Gennadiy S. Patrin Vitaliy A. Orlov Yaroslav G. Shiyan Aleksandr V. Kobyakov

We present a study of [(CoP)soft/(NiP)am/(CoP)hard/(NiP)am]n (n ≤ 20) magnetic superlattices (tCoP = 5 nm, tNiP = 4 nm) synthesized via chemical bath deposition (CBD). Atomic force microscopy reveals that the soft magnetic layer is fine-grained (amorphous), whereas the hard magnetic layer exhibits a polycrystalline hexagonal structure. The results demonstrate a long-range interlayer interaction whose magnitude depends on the number of blocks (n). This interaction manifests as multiple resonance peaks in the magnetic resonance spectra: three peaks were observed for structures with n = 5, 10, and 15, while two peaks were identified for n = 20. Temperature dependencies of the interlayer interaction fields were obtained: the interaction between the nearest magnetically hard and soft layers is negative (HJ1 < 0), while the interaction between the soft layers (HJ2) undergoes a sign reversal from positive to negative with increasing temperature at a threshold temperature depending on n. The oscillations of the magnetization saturation field correlate with the magnetic anisotropy fields.

Magnetochemistry doi: 10.3390/magnetochemistry12030032

Authors: Vidak Raičević Niko S. Radulović Katarina Urumović Nebojša Kladar Branislava Srđenović Čonić

Equilenin is an equine estrogen constituting the basis of a highly-prescribed pharmaceutical preparation. Although routine 1H and 13C NMR data for it have been reported, complete assignments and a full analysis of the proton spin system have not been established. In the present study, equilenin was examined by solution NMR in deuterochloroform, employing conventional spectral analysis in conjunction with quantum-mechanical techniques to achieve a 1H iterative full spin analysis (HiFSA). The resulting model reproduces the experimental spectrum with high fidelity and permits the determination of true chemical shifts and scalar coupling constants for this complex spin system. In addition, the 13C NMR spectrum was fully assigned using a combination of one- and two-dimensional experiments. The obtained data constitute a robust spectroscopic reference set for equilenin and the analytical value of the Cosmic Truth software for resolving spin systems in steroids. The results provide a valuable source of data for researchers seeking to implement NMR-based assays relevant to analytical, regulatory, and forensic applications.

Magnetochemistry doi: 10.3390/magnetochemistry12030031

Authors: Liliane A. S. Angelo Alexandra A. P. Mansur Sandhra M. Carvalho Klaus Krambrock Isadora C. Carvalho Herman S. Mansur

Regrettably, glioblastoma multiforme (GBM) remains the deadliest form of brain cancer, with a very unfavorable prognosis for life expectancy for the patient. We report, for the first time, the green colloidal synthesis of cobalt-doped magnetic iron oxide nanoparticles (Co-MNPs) as aqueous ferrofluids, using two anionic polysaccharide biopolymers, hyaluronic acid (HA) and carboxymethyl cellulose (CMC), as surfactants. These ferrofluids based on magnetite nanoparticles (HA@Co-MNP and CMC@Co-MNP) demonstrated superparamagnetic properties and magnetic-to-thermal conversion upon exposure to an alternating magnetic field (AMF), with the extent of conversion dependent on surfactant type. In addition, the ferrophase acted as a nanozyme, mimicking peroxidase-like activity in response to hydrogen peroxide, which is present at higher levels in tumor cells. The coupling of magnetic-heat capabilities with biocatalytic behavior enhances glioblastoma cell elimination and suppresses 3D neurospheroid growth. The results also showed that active targeting based on the HA biopolymer shell, due to its affinity for CD44 membrane receptors overexpressed in GBM, outperformed CMC-coated ferrofluid analogs. These magnetocatalytic-responsive nanoplatforms offer a broad avenue for the diagnosis and therapy of numerous cancers, potentially improving patients’ quality of life and prognoses.

Magnetochemistry doi: 10.3390/magnetochemistry12030030

Authors: Viviana B. Daboin Julieta S. Riva Paula G. Bercoff

Magnetic-field-assisted electrocatalysis offers a powerful route to enhance the oxygen evolution reaction (OER) by coupling spin-dependent effects with magnetohydrodynamic phenomena. Here, we present a unified study of cobalt ferrite (CoFe2O4)-based nanofilms, elucidating the combined roles of rare-earth doping, nanoparticle size, film morphology, and electrode substrate magnetism on OER performance under external magnetic fields. The effect of UV-light irradiation is also investigated. CoFe2O4 and yttrium-doped CoFe2O4 nanoparticles were synthesized via thermal decomposition and self-combustion routes, yielding single-domain particles with distinct structural and magnetic properties, and assembled into homogeneous nanofilms using the Langmuir–Blodgett technique. Electrocatalytic measurements in alkaline media reveal that intrinsic OER activity is primarily governed by film compactness and charge-transfer efficiency, while the magnitude of magnetic-field-induced enhancement depends on the magnetic response of both the nanofilms and the supporting electrode. Ferromagnetic substrates promote enhanced catalytic activity under magnetic fields, whereas diamagnetic substrates can exhibit suppressed performance. Across all systems, the strongest enhancement is observed when the magnetic field is applied parallel to the electrode surface, reflecting the combined effects of spin polarization and Lorentz-force-driven mass transport. UV-light irradiation is also evaluated as an external stimulus to promote the reaction. Our findings establish a comprehensive framework for designing magnetically assisted OER electrocatalysts and demonstrate that magnetic-field effects can rival or complement rare-earth doping or UV-light irradiation, offering a sustainable pathway toward high-efficiency water oxidation.

Magnetochemistry doi: 10.3390/magnetochemistry12030029

Authors: Andrew Palii Valeria Belonovich Boris Tsukerblat

In this article, we extend the recently proposed theoretical framework for nonequilibrium magnetothermal effects induced by a sudden magnetic field quenching to anisotropic 3d-metal complexes with arbitrary spins. The formalism is applicable not only to the case of complete magnetic field switching off, but also to the case of partial field quenching. A simple and universal semiquantitative rule is formulated, which allows for the prediction of the sign of a thermal effect (that means heat absorption or heat release) from the magnetic field dependencies of the spin energy levels. In many specific cases, this rule can be used to predict the sign of the magnetothermal effect prior to calculations, based on an analysis of the field dependencies of the spin levels of the complexes under study. According to this rule, each excited state contributes to cooling or heating depending on whether it becomes destabilized or stabilized as the field decreases. The performed numerical analysis of the specific heat release, as a function of temperature and initial and final magnetic fields for complexes with spins S = 1, 3/2, 2, and 5/2, demonstrates that systems with easy-axis magnetic anisotropy (D < 0) exhibit heat absorption in cases of complete and incomplete field quenching, with the effect being strongly enhanced in the latter case. In contrast, in complexes with easy-plane-type anisotropy (D > 0), the sign of the thermal effect is shown to be dependent on the temperature, the initial and final values of the magnetic field, and also on whether the spin of the complex is integer or half-integer. These results provide clear and practical guidelines for the design of low-temperature molecular magnetic refrigerants operating in fast field-quenching regimes.

Magnetochemistry doi: 10.3390/magnetochemistry12030028

Authors: Yanzhen Han Shiyao Chong Jingjing Du Xiaolan Liu Haili Guo Ruikai Wang Mingyue Hui

Long-range hopping plays a crucial regulatory role in non-Hermitian topological systems. This paper systematically studies a non-Hermitian Su–Schrieffer–Heeger (SSH) model that incorporates both long-range hopping and spin–orbit coupling (SOC) within the framework of the generalized Brillouin zone (GBZ). We reveal that long-range hopping can not only actively suppress the non-Hermitian skin effect, but can also cooperate with SOC to jointly modulate the stability regions of topological phases. SOC controls topological transitions through real or imaginary coupling properties and enhances the robustness of edge states. By constructing the GBZ and establishing the non-Bloch bulk–boundary correspondence, we demonstrate that the topological zero modes are entirely determined by the non-Bloch winding number. This study clarifies the key role of long-range hopping as a core regulatory parameter and provides a new paradigm for achieving the synergistic control of topological states and localized properties in non-Hermitian systems through designed couplings.

Magnetochemistry doi: 10.3390/magnetochemistry12020027

Authors: Mauricio Galvis Fredy Mesa César Leandro Londoño-Calderón

This work presents a detailed micromagnetic analysis of the magnetization reversal process in hollow iron nanospheres with a shell thickness of 16 nm. Using the Ubermag computational framework coupled to the OOMMF, we demonstrate that these nanospheres exhibit high coercivity and remanence, producing elongated hysteresis loops, consistently with previous experimental findings. The reversal process is governed by the nucleation and evolution of non-collinear magnetic domains and domain walls, as revealed by magnetization mapping. A comprehensive energetic evaluation indicates a dynamic competition among anisotropy, exchange, Zeeman, and demagnetizing energies, with the latter exerting a dominant influence on the final magnetic configuration. These results enhance our understanding of the magnetic behavior in hollow nanostructures and provide a theoretical foundation for their application in spintronic and biomedical systems.

Magnetochemistry doi: 10.3390/magnetochemistry12020026

Authors: Gaihui Liu Xie Huang Shuaishuai Liu Xiangzhou Yan Nan Dong Huihui Shi Fuchun Zhang Suqin Xue

In this study, the synergistic effects of Fe doping and oxygen vacancies on the structural, electronic, and optical properties of Bi4O5Br2, as well as their influence on the photocatalytic CO2 reduction mechanism, were systematically explored through first-principles calculations. The results reveal that Fe-doped, oxygen-defective, and Fe–Vo co-modified Bi4O5Br2 systems exhibit excellent thermodynamic and dynamic stability. Oxygen vacancies introduce defect states near the Fermi level, narrowing the band gap and enhancing charge localization and CO2 adsorption, while Fe doping induces strong spin polarization and introduces Fe 3d impurity levels that effectively couple with O 2p orbitals, promoting charge transfer and visible-light absorption. The coexistence of Fe dopants and oxygen vacancies produces a significant synergistic effect, forming a continuous energy-level bridge that enhances charge separation and broadens the light absorption range. Gibbs free energy analyses further demonstrate that the Fe–Vo–BOB system exhibits the lowest energy barriers and the most favorable thermodynamics for CO2-to-CO conversion. This study provides deep insight into the defect–dopant synergy in Bi4O5Br2 and offers valuable theoretical guidance for engineering highly efficient visible-light-driven photocatalysts in solar energy conversion and environmental remediation.

Magnetochemistry doi: 10.3390/magnetochemistry12020025

Authors: Peng Cheng You Song Hui-Zhong Kou Jinkui Tang

This Special Issue of Magnetochemistry is dedicated to Professor Dai-Zheng Liao on the occasion of his 85th birthday [...]

Magnetochemistry doi: 10.3390/magnetochemistry12020024

Authors: Nuo Cheng Song-Tao Yang Ding Ding Lei Xia

In the present work, we selected an amorphous Nd60Ni40 alloy as a basic alloy and added Er with a higher effective magnetic moment and de Gennes factor to replace Nd for the purpose of improving the magnetocaloric performance of the Nd60Ni40 amorphous alloy. The formability, magnetization, and magnetocaloric behaviors of the Nd60-xErxNi40 (x = 5, 10, 15, 20) amorphous alloys were studied. It was found that Er substitution generally improved the glass formability, but simultaneously decreased the Curie temperature, coercivity, and magnetic entropy change peak of the basic alloy. The mechanism for these unexpected results was investigated, and it was supposed that the decreased Curie temperature and the deteriorated magnetocaloric properties may have resulted from the antiferromagnetic coupling between the Nd and Er atoms.

Magnetochemistry doi: 10.3390/magnetochemistry12020023

Authors: Lays da Silva Sá Gomes Daniel Ângelo Macena Maryane Pipino Beraldo Almeida Naiara Maria Pavani Iara Souza Lima Aroldo Geraldo Magdalena Oswaldo Baffa Angela Kinoshita

Sugarcane vinasse is a high-strength effluent with a high organic load and intense coloration from melanoidins and phenolic compounds, making conventional biological treatment difficult. This study presents a magnetically recoverable Fe3O4@latex-ZnO nanocomposite, synthesized using natural Hevea brasiliensis latex as a green polymeric interlayer. Transmission Electron Microscopy (TEM) shows a core–shell structure that enhances ZnO anchoring and reduces aggregation. X-ray Diffraction (XRD) confirms the coexistence of spinel Fe3O4 and wurtzite ZnO without secondary phases, while Fourier Transformed Infrared Spectroscopy (FTIR) verifies the latex layer through characteristic organic bands, indicating a stable organic–inorganic interface. Under 4 h of UV irradiation, the nanocomposite significantly reduced vinasse COD from 23,450 to 12,450–13,150 mg L−1 (≈44–47%) and BOD from 11,600 to 4800–5000 mg L−1 (≈57–59%), demonstrating substantial oxidation of the organic fraction. The magnetic core enables quick separation post-treatment, enhancing the practicality of the process. Overall, this innovative approach positions the ZnO nanocomposite as a promising option for vinasse pre-treatment and integrated agro-industrial effluent treatment.

Magnetochemistry doi: 10.3390/magnetochemistry12020022

Authors: Amit Rajput Akram Ali Himanshu Arora Akhilesh Kumar

The ligand-driven self-assembly of metal clusters offers a powerful strategy for constructing discrete molecular architectures with tunable magnetic and structural properties. By judiciously selecting appropriate multidentate ligands, researchers can direct the formation of polynuclear metal assemblies with diverse nuclearities, geometries, and topologies. Coordination-driven processes commonly stabilize such assemblies where multidentate ligands operate as templates and linkers. These will also determine how the metal centers are arranged in space and how they connect to each other. These clusters can take on shapes that range from basic bridging dimers to more complicated icosahedral and cubane-type motifs. They often have excellent symmetry and strong frameworks. Magnetically, these clusters are a great place to study exchange interactions, spin frustration, and the behavior of single-molecule magnets (SMMs). The magnetic characteristics depend on things like the type of metal ions, the bridging ligands, the overall shape, and the local coordination environment. Interestingly, a large number of ligand-assembled clusters exhibit high spin ground states and slow magnetization relaxation, which makes them attractive options for quantum information storage and molecular spintronic devices. This review connects coordination chemistry, supramolecular design, and molecular magnetism of pyridine–amine–carboxylate frameworks, offering insights into fundamental magnetic phenomena and guiding the development of next-generation functional materials. Continued exploration of ligand frameworks and metal combinations holds the potential to yield novel clusters with enhanced or unprecedented magnetic characteristics.

Magnetochemistry doi: 10.3390/magnetochemistry12020021

Authors: Thiago Tiburcio Vicente Prabu Periyathambi Ariane Franson Sanches Marina Yuki Azevedo Nakakubo Nicholas Zufelato Karina Bezerra Salomão María Sol Brassesco Theo Zeferino Pavan Koiti Araki Antônio A. O. Carneiro

The tumor microenvironment, characterized by higher acidity, hypoxia, and dense cellular structures, plays a pivotal role in cancer progression, therapeutic resistance, and treatment response. Nanoparticle-based contrast agents enable the precise delineation of solid regions within heterogeneous tumors through advanced molecular imaging techniques. Since 1956, ultrasound (US) medical imaging has provided essential anatomical and functional insights about internal organs. More recently, magnetomotive ultrasound (MMUS) has emerged as a promising imaging modality, using a modulated magnetic field to exert force on superparamagnetic iron oxide nanoparticles (SPIONs), inducing motion in the surrounding tissues through mechanical coupling. In parallel, magnetic hyperthermia (MH), which employs localized heating by alternating magnetic fields, has demonstrated significant potential in selectively destroying cancer cells while sparing healthy tissues. This review summarizes the current state of IONP-based contrast agents, with particular emphasis on their use in MH for cancer treatment, as well as their potential in multimodal imaging, including MMUS, and photoacoustic (PA) imaging. The advantages and limitations of IONPs in tumor detection and characterization are discussed, examining the development of surface-functionalized MNPs, and analyzing how material properties and environmental factors affect their diagnostic and therapeutical performance. Finally, strategies for combining MMUS and PA modalities for pre-clinical cancer imaging are proposed.

Magnetochemistry doi: 10.3390/magnetochemistry12020020

Authors: Miaotian Zhang Licong Jin Yu Feng

Magnetic fluid sealing is a novel sealing technology wherein magnetic fluids play a pivotal role in the sealing process. The yield stress of the magnetic fluid directly affectsits sealing performance and is governed by multiple interdependent factors. Conventional approaches that evaluate the effect of a single parameter while keeping other parameters constant are insufficient to fully characterize the relative contributions of each parameter to the yield stress. In this study, we investigate the preparation factors affecting the yield stress of kerosene-based magnetic fluids and propose a parameter sensitivity analysis method based on orthogonal experimental design to determine the optimal combination of factor levels within the studied range. The sensitivity of key preparation factors affecting the yield stress of kerosene-based magnetic fluids was determined via range and variance analyses of the orthogonal experimental data. The factors, ranked in descending order of sensitivity, were surfactant (C18H34O2) dosage, precipitant (NH3·H2O) dosage, and deionized water (H2O) volume. Moreover, the effects of different levels of the same factor were analyzed using multiple approaches. These findings provide a theoretical foundation for optimizing the preparation of magnetic fluids and enhancing their sealing performance.

Magnetochemistry doi: 10.3390/magnetochemistry12020019

Authors: Zayan Ahsan Ali Preeti Tewatia Oliver Waldmann

Lanthanide-based single-molecule magnets are promising candidates for potential applications. Their magnetism is governed by ligand-field splittings, which may require up to 27 ligand-field parameters for accurate modeling. Determining these parameters reliably from measured data is a major challenge, for which machine learning approaches offer promising solutions. We provide an overview of these approaches and present our perspective on addressing the inverse problem relating experimental data to ligand-field parameters. Previously, a machine learning architecture combining a variational autoencoder (VAE) and an invertible neural network (INN) showed promise for analyzing temperature-dependent magnetic susceptibility data. In this work, the VAE-INN model is extended through data augmentation to enhance its tolerance to common experimental inaccuracies. Focusing on second-order ligand-field parameters, diamagnetic and molar-mass errors are incorporated by augmenting the training dataset with experimentally motivated error distributions. Tests on simulated experimental susceptibility curves demonstrate substantially improved prediction accuracy and robustness when the distributions correspond to realistic error ranges. When applied to the experimental susceptibility curve of the complex Al2IIIEr2III, the augmented VAE–INN recovers ligand-field solutions consistent with least-squares benchmarks. The proposed data augmentation thus overcomes a key limitation, bringing the ML approach closer to practical use for higher-order ligand-field parameters.