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.

Magnetochemistry doi: 10.3390/magnetochemistry12020018

Authors: Xiaoying Li Li Wei Lianqi Li Junying Suo Shuai Li Honggang Jiang

In this work, four different magnetic Fe3O4 nanoparticles are prepared via solvothermal method. According to the morphology, the products can be divided into flower-like Fe3O4 (F-Fe3O4), solid spherical Fe3O4 (S-Fe3O4), hollow spherical Fe3O4 (HO-Fe3O4), and hexahedral Fe3O4 (HE-Fe3O4). A set of measurements is performed to confirm the structure, composition, and pore properties of the obtained materials. The catalytic activities of the prepared materials are examined and compared. The results prove that the four materials have an intrinsic catalytic property. HO-Fe3O4 ranks first in the catalytic activity mainly due to its large surface area and reasonable element composition. The maximum specific saturation magnetization and specific surface area of HO-Fe3O4 are 72.94 emu/g and 42.60 m2/g. Fe2+/Fe3+ in HO-Fe3O4 is 51.5%. It is found that HO-Fe3O4 possesses fantastic stability and perfect reproducibility as it is used as a catalyst several times without significant loss in its activity.

Magnetochemistry doi: 10.3390/magnetochemistry12020017

Authors: Jimei Niu Zhigang Zheng Hongyu Wang

To enhance the wide-temperature-range magnetocaloric performance of (Mn,Fe)2(P,Si) alloys, the effects of Mg-Co co-doping on their structural and magnetocaloric properties were systematically investigated. Mn1.05−yCoyFe0.9P0.5Si0.48Mg0.02 alloys were prepared by the arc melting method. The results show that Mg-Co co-doping can tune the lattice parameters and ferromagnetic coupling between Mn and Fe atoms. The Mn1.03Co0.02Fe0.9P0.5Si0.48Mg0.02 alloy exhibited an effective refrigeration capacity of 425.4 J·kg−1 and an effective working temperature span of 52 K. During the temperature-induced ferromagnetic transition, coupling between the magnetic moment of Fe-Si layers and the crystal lattice drives a magnetoelastic transition, leading to a giant magnetocaloric effect. The Mg-Co co-doping strategy effectively tunes the crystal structure and local electron density distribution of the Fe-Si layer, thereby influencing the total magnetic moment and magnetothermal properties of the alloys.

Magnetochemistry doi: 10.3390/magnetochemistry12020016

Authors: Carolina Otonelo Carla Layana Elisa de Sousa Luciana Juncal Melina D. Ibarra Constanza Toledo Alejo Melamed Karen L. Salcedo Rodríguez Patricia L. Schilardi Lucia Poleri Carlos Golijow Sheila Ons Pedro Mendoza Zélis Claudia Rodríguez Torres

In this work, we evaluate the efficiency of a DNA purification protocol from gynecological samples using locally synthesized Fe3O4@SiO2 magnetic microparticles and a low-cost, guanidinium thiocyanate (GITC)-free lysis buffer. The microparticles were characterized by SEM, EDS, FTIR, and magnetic measurements, confirming the formation of compact silica-coated aggregates with suitable magnetic responsiveness for rapid and complete capture. Using this material in combination with a simple, GITC-free lysis buffer, we achieved DNA extraction yields comparable to those obtained with standard methods based on chaotropic salts. The purified DNA showed high compatibility with molecular assays for the detection of Chlamydia trachomatis, Ureaplasma urealyticum, Mycoplasma hominis, and human papilloma virus. Clinical validation demonstrated excellent diagnostic performance, with only a few discrepancies observed in samples near the detection threshold of qPCR, a limitation shared with commercial kits. Overall, the method represents a low-cost, safe, and sustainable alternative for routine clinical and epidemiological applications, compared to methods based on chaotropic salt buffers. Furthermore, it reduces reliance on imported commercial consumables and minimizes the handling of hazardous reagents.

Magnetochemistry doi: 10.3390/magnetochemistry12010015

Authors: Shu-Ping Chen Sandra M. Taylor Sai Huang Baoling Zheng

Based on our deconvolution result of the Tetraphenyl porphyrin nuclear magnetic resonance (NMR) spectrum, we initiated a goodness-of-fitting evaluation by overlaying the third-order derivatives of the native NMR spectrum and the entire reconstructed spectrum to appraise the accuracy of the reverse curve fitting method. Then, the same NMR overlapping band was deconvoluted by even-order derivatives and Fourier self-deconvolution, respectively. The reverse curve fitting demonstrated its superior achievements to the other two methods in the comparative assessment. Meanwhile, three traditional window functions (Bessel, Hamming, and 3-term Blackman–Harris) were examined for their apodization effects which will benefit reverse curve fitting performance.

Magnetochemistry doi: 10.3390/magnetochemistry12010014

Authors: Seong-Hyeon Kang Jun-Young Chung Youngjin Lee for The Alzheimer’s Disease Neuroimaging Initiative for The Alzheimer’s Disease Neuroimaging Initiative

Brain magnetic resonance imaging (MRI) is highly susceptible to motion artifacts that degrade fine structural details and undermine quantitative analysis. Conventional U-Net-based deep learning approaches for motion artifact reduction typically operate only in the image domain and are often trained on data with simplified motion patterns, thereby limiting physical plausibility and generalization. We propose Sim-DDNet, a simulation-data-based dual-domain network that combines k-space-based motion simulation with a joint image-k-space reconstruction architecture. Motion-corrupted data were generated from T2-weighted Alzheimer’s Disease Neuroimaging Initiative brain MR scans using a k-space replacement scheme with three to five random rotational and translational events per volume, yielding 69,283 paired samples (49,852/6969/12,462 for training/validation/testing). Sim-DDNet integrates a real-valued U-Net-like image branch and a complex-valued k-space branch using cross attention, FiLM-based feature modulation, soft data consistency, and composite loss comprising L1, structural similarity index measure (SSIM), perceptual, and k-space-weighted terms. On the independent test set, Sim-DDNet achieved a peak signal-to-noise ratio of 31.05 dB, SSIM of 0.85, and gradient magnitude similarity deviation of 0.077, consistently outperforming U-Net and U-Net++ across all three metrics while producing less blurring, fewer residual ghost/streak artifacts, and reduced hallucination of non-existent structures. These results indicate that dual-domain, data-consistency-aware learning, which explicitly exploits k-space information, is a promising approach for physically plausible motion artifact correction in brain MRI.

Magnetochemistry doi: 10.3390/magnetochemistry12010013

Authors: Mehmet Emre Aköz Frowin Dörr Ahmet Yavuz Oral Yasser Shokr

Perpendicular magnetic tunnel junctions (p-MTJs) rely on synthetic antiferromagnets (SAFs) as reference layers to achieve strong perpendicular magnetic anisotropy (PMA) together with stable interlayer exchange coupling. In this study, we present a comparative materials study of buffer and spacer layer engineering in Co/Pt-based perpendicular synthetic antiferromagnets (p-SAFs). The influence of buffer layer selection, number of multilayer repeats, and annealing at 330 °C for 30 min on PMA and interlayer exchange coupling is systematically examined. Co/Pt multilayers with four and six repeats were grown on Ta/Ru and Ta/CuN buffer layers separately, followed by the fabrication of SAF structures incorporating Ru spacers with thickness between 0.60 and 0.80 nm. Magnetic measurements show that Ta/Ru-buffered structures exhibit squarer hysteresis loops, higher remanence, and greater tolerance to annealing at 330 °C for 30 min compared to Ta/CuN-buffered counterparts. The SAF structures display clear two-step magnetization reversal and robust antiferromagnetic coupling across the investigated Ru thickness range, with large exchange fields and bias fields in the deposited state. Although annealing reduces the absolute coupling strength, a Ru spacer thickness of 0.60 nm retains the strongest antiferromagnetic response within the studied thermal budget. These results underscore the importance of comparative buffer and spacer layer engineering and provide materials insights into the design of Co/Pt-based p-SAF reference stacks that may inform future p-MTJ structures.

Magnetochemistry doi: 10.3390/magnetochemistry12010012

Authors: Włodzimierz Makulski

High-resolution NMR spectroscopy is the leading method for determining nuclear magnetic moments. It is designed to measure stable nuclei, which can be investigated in macroscopic samples. In this work, we discuss the progress in research into light nuclei from the first three periods of the Periodic Table and several selected heavy nuclides. The 1H and 3He nuclear magnetic moments, established using the new double Penning trap facility, are also considered. Both nuclei can be used as references in gaseous mixtures. Gas-phase NMR spectroscopy enables precise measurements of the frequencies and shielding constants of isolated single molecules. They can be used to determine new, accurate nuclear magnetic moments of nuclides in stable, gaseous substances. Particular attention is paid to the importance of diamagnetic corrections for obtaining accurate results. Finding precise diamagnetic corrections—shielding factors —even for light nuclei in molecules is a significant challenge. To date, nuclear moments have been obtained primarily from experimental data. The theoretical approach is mostly unable to predict these values accurately. Some remarks are also made on pure theoretical treatments of nuclear moments.

Magnetochemistry doi: 10.3390/magnetochemistry12010011

Authors: Yuxi Lin Chen Chen Wei Xu

The increasing energy crisis demands sustainable functional materials. Wood, with its natural three-dimensional porous structure, offers an ideal renewable template. This study demonstrates that microstructural engineering of wood is a decisive strategy for enhancing magnetothermal conversion. Using eucalyptus wood, we precisely tailored its pore architecture via delignification and synthesized Fe3O4 nanoparticles in situ through coprecipitation. We systematically investigated the effects of delignification and precursor immersion time (24, 48, 72 h) on the loading, distribution, and magnetothermal performance of the composites. Delignification drastically increased wood porosity, raising the Fe3O4 loading capacity from ~5–6% (in non-delignified wood) to over 14%. Immersion time critically influenced nanoparticle distribution: 48 h achieved optimal deep penetration and uniformity, whereas extended time (72 h) induced minor local agglomeration. The optimized composite (MDW-48) achieved an equilibrium temperature of 51.2 °C under a low alternating magnetic field (0.06 mT, 35 kHz), corresponding to a temperature rise (ΔT) > 24 °C and a Specific Loss Power (SLP) of 1.31W·g−1. This performance surpasses that of the 24 h sample (47 °C, SLP = 1.16 W·g−1) and rivals other bio-based magnetic systems. This work establishes a clear microstructure–property relationship: delignification enables high loading, while controlled impregnation tunes distribution uniformity, both directly governing magnetothermal efficiency. Our findings highlight delignified magnetic wood as a robust, sustainable platform for efficient low-field magnetothermal conversion, with promising potential in low-carbon thermal management.

Magnetochemistry doi: 10.3390/magnetochemistry12010010

Authors: Shuaibing Chang Feng Li Jiewen Deng

The tokamak is a toroidal device that utilizes magnetic confinement to achieve controlled nuclear fusion. One of the major technical challenges hindering the development of this technology lies in effectively dissipating the generated heat. In this study, the inner blanket structure of a tokamak is selected as the research object, and a multi–physics numerical model coupling magnetic field, temperature field, and flow field is established. The effects of background magnetic field strength, blanket channel width, and inlet velocity of the liquid metal coolant on the thermal–flow characteristics of the blanket were systematically investigated. The results indicate that compared with the L-shaped channel, the U-shaped channel reduces flow resistance in the turning region by 6%, exhibits a more uniform temperature distribution, and decreases the outlet–inlet temperature difference by 4%, thereby significantly enhancing the heat transfer efficiency. An increase in background magnetic field strength suppresses coolant flow but has only a limited impact on the temperature field. When the background magnetic field reaches a certain strength, the magnetic field has a certain hindering effect on the flow of the working fluid. Increasing the thickness of the blankets appropriately can alleviate the hindering effect of the magnetic field on the flow and improve the velocity distribution in the outlet area.

Magnetochemistry doi: 10.3390/magnetochemistry12010009

Authors: Serge L. Smirnov

In recent years, research in the areas of Biological Chemistry and Medicine has been advancing along many directions including those centered around NMR spectroscopy and imaging [...]

Magnetochemistry doi: 10.3390/magnetochemistry12010008

Authors: Guorong Sha Liang Jiang Chao Yang Zenglu Song Yasushi Takemura

The Wiegand effect is a nonlinear magnetic phenomenon observed in specially processed Wiegand wires, representing a macroscopic manifestation of the Barkhausen effect. It is characterized by a large, sharp Barkhausen jump in the wire’s magnetization curve under an external alternating magnetic field. However, the underlying magnetic structure of these wires and the precise mechanism responsible for the Wiegand effect remain inadequately understood. In this study, we propose a conceptual model for the magnetic structure of Wiegand wires. Experimental samples with varying diameters were prepared through FeCl3 solution etching. The magnetic properties of individual layers within the wire were systematically investigated using the surface magneto-optic Kerr effect, Wiegand pulse measurements, and minor hysteresis loop analysis. By correlating these experimental results with JMAG simulations based on the proposed magnetic structure model, we elucidate the layer-by-layer magnetization reversal processes under alternating magnetic fields and clarify the fundamental mechanism that triggers the large Barkhausen jump.

Magnetochemistry doi: 10.3390/magnetochemistry12010007

Authors: Xiaoyan Shen Hongkui Zhong Ruiqing Han

Magnetic core loss is an important indicator for describing the performance of magnetic elements. The traditional physical model has an insufficient performance for predicting the magnetic core loss of magnetic elements under complex conditions such as high temperature, non-sinusoidal waveform, and high frequency. To address this issue, this study proposes a physics-informed neural network (PINN)-based model for magnetic core loss prediction. In particular, this PINN-based model is constructed with a hybrid network architecture as a baseline algorithm, which combines a convolutional long short-term memory network (Conv-LSTM), power spectral density (PSD), and an ensemble learning method (including extreme gradient boosting (XGB), gradient boosting regression (GBR), and random forest (RF)). This design aims to address the complexity of magnetic core loss prediction. Moreover, the Steinmetz equation (SE) is improved to enhance the adaptability under complex conditions, and this improved Steinmetz equation (ISE) is integrated as physical constraints embedded in the neural network for magnetic core loss prediction. Based on the traditional data-driven loss term, the physical residual term is introduced as a regularization constraint to enable the prediction to satisfy both the observed data distribution and physical law. The experimental results show that the PINN-based model has a good prediction performance of magnetic core loss under complex conditions.

Magnetochemistry doi: 10.3390/magnetochemistry12010006

Authors: Jingwen Zhang Cunhao Lu Jian Chen Yaoji Deng

Predicting core loss under high-frequency non-sinusoidal excitation is crucial for power electronics equipment design. Temperature significantly affects core loss, and traditional core loss prediction models typically incorporate temperature corrections to enable accurate loss estimation across varying temperatures. Based on the Modified Steinmetz Equation (nonT-MSE) model, this study considers the temperature effect by employing a combination of the Tanh function and a linear term to modify the three empirical parameters, with the Tanh function capturing the nonlinear saturation of the loss coefficient k with increasing temperature. This leads to the establishment of the temperature-corrected non-TMSE (T-MSE) model for predicting magnetic core loss under high-frequency non-sinusoidal excitation. During model derivation, training data undergo logarithmic transformation processing. Subsequently, with T-MSE empirical parameters as variables and the minimum mean squared error between T-MSE predicted values and experimental values as the objective function, a single-objective optimization model is established. Finally, the empirical parameters of T-MSE are calculated using the training data and the single-objective optimization model. Comparing the core loss experimental results of the four materials, the average MSE values for the T-MSE model, the nonT-MSE model, and the square-root temperature-corrected non-TMSE model proposed by Zeng et al. (Zeng) are 0.0082, 0.0459, and 0.0110, respectively; with average MAPE of 1.57%, 1.87%, and 2.17%, respectively; and average R2 of 0.9862, 0.9807, and 0.9731. Compared to the nonT-MSE model and the Zeng model, the T-MSE model demonstrated higher prediction accuracy.

Magnetochemistry doi: 10.3390/magnetochemistry12010005

Authors: Iosif Malaescu Paul C. Fannin Catalin N. Marin Madalin O. Bunoiu

For the study, we used four kerosene-based ferrofluid samples containing magnetite nanoparticles stabilized with oleic acid. Starting from the initial sample (A0), the other three samples were obtained by dilution with kerosene. The complex magnetic permeability measurements were performed in the microwave region (0.5–6) GHz, for different H values of the polarizing magnetic field, between (0–115) kA/m. These measurements revealed the ferromagnetic resonance phenomenon for each sample, allowing the determination of the anisotropy field (HA) and the effective anisotropy constant (Keff) of nanoparticles, depending on the volume fraction of particles (φ). At the same time, the measurements allowed the determination of the specific magnetic loss power (pm), effective heating rate (HReff), intrinsic loss power (ILP), and specific absorption rate (SAR) as functions of the frequency (f) and magnetic field (H), of all investigated samples, using newly proposed equations for their calculation. For the first time, this study evaluates the maximum limit of the applied polarizing magnetic field (Hmax ≈ 80 kA/m) and the minimum limit volume fraction of nanoparticles (φmin ≈ 3.5%) at which microwave heating of the ferrofluid remains efficient. At the same time, the results obtained show that the temperature increase of the ferrofluid samples, upon interaction with a microwave field, can be controlled by varying both H and φ, pointing to possible applications in magnetic hyperthermia.

Magnetochemistry doi: 10.3390/magnetochemistry12010004

Authors: Wenhui Ping Juan Yang Xiaohong Cheng Weibing Zhang Yilan Shi Qinghua Yang

The contamination of water bodies by polycyclic aromatic hydrocarbons (PAHs) poses a significant concern for the ecological systems, along with public health. Magnetic adsorption stands out as a green and practical solution for treating polluted water. To make the process more efficient and economical, it is important to create materials that not only absorb contaminants effectively but also allow for easy recovery and reuse. This study proposes a simple yet effective method for coating Fe3O4 nanoparticles with hydroxypropyl-β-cyclodextrin polymer (HP-β-CDCP). The physicochemical properties of the synthesized sorbent were characterized using a transmission electron microscope (TEM), Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and Vibrating Sample Magnetometer (VSM) analysis. The adsorption performance of HP-β-CDCP/Fe3O4 nanoparticles was well-described by the pseudo-second-order kinetic model, thermodynamic analysis, and the Freundlich isotherm model, indicating multiple interaction mechanisms with PAHs, such as π–π interactions, hydrogen bonding, and van der Waals forces. Using HP-β-CDCP/Fe3O4 nanoparticles as the adsorbent, the purification rates for the fifteen representative PAHs were achieved within the range of 33.9–93.1%, compared to 15.3–64.8% of the unmodified Fe3O4 nanoparticles. The adsorption of all studied PAHs onto HP-β-CDCP/Fe3O4 nanocomposites was governed by pH, time, and temperature. Equilibrium in the uptake mechanism was obtained within 15 min, with the largest adsorption capacities for PAHs in competitive adsorption mode being 6.46–19.0 mg·g−1 at 20 °C, pH 7.0. This study points to the practical value of incorporating cyclodextrins into tailored polymer frameworks for improving the removal of PAHs from polluted water.

Magnetochemistry doi: 10.3390/magnetochemistry12010003

Authors: Sicheng Zhai Xiaoqiang Li Changkuan Zheng Qun Wang

Ball milling treatment facilitates the transformation of carbonyl iron powders from a spherical to a flaky morphology, while simultaneously introducing numerous defects that approach the nanometer scale in one dimension. Flaky iron nitride was synthesized via the gas nitridation in an NH3/N2 atmosphere. The microstructure, morphology, and magnetic properties of the samples nitrided at different temperatures were characterized using XRD, SEM, TEM, and VSM. The formation of γ′-Fe4N and ε-Fe3N phases impedes domain wall movement, resulting in a slight increase in the Hc of the samples. Notably, γ′-Fe4N positively influences the magnetic properties of iron nitride. As the nitriding temperature rises, the content of the γ′-Fe4N phase initially increases before subsequently declining. Consequently, the flaky iron nitride synthesized at 610 °C exhibits excellent soft magnetic properties with a high Ms value reaching up to 177.1 emu/g and a low Hc value, indicating its potential applications in the field of magnetic materials.

Magnetochemistry doi: 10.3390/magnetochemistry12010002

Authors: Yongfei Guo Mao Yang Yan Wang Zhigang Tian Tongguo Si

Developing precise tumor-targeting delivery systems while minimizing off-target toxicity continues to pose significant challenges in medicine application. The integration of two different functional materials has emerged as a promising strategy in current biomedical research. Herein, a hybrid nanocomposite consisting of Fe3O4 and ZnO was synthesized via a simple approach and employed as a nanoscale drug delivery system to explore the loading capacity and stimuli-responsive release characteristics of the anticancer agent doxorubicin (DOX). Results show that the synthesized nanoparticles (NPs) exhibit a multi-scale nanostructure consisting of the spindle-like ZnO nanorods with a mean length of 280 nm, on which the Fe3O4 NPs with a diameter of around 16 nm are uniformly dispersed. The ZnO@Fe3O4 NPs possess superparamagnetic behavior and a fast response to the external magnet and demonstrate exceptional near-infrared (NIR) photothermal conversion efficiency. In drug release studies, the ZnO@Fe3O4 NPs achieve the controlled DOX release in the simulated acidic tumor microenvironment as well as NIR laser irradiation. Further, the ZnO@Fe3O4-DOX composites significantly suppress the viability of human cervical cancer cells (HeLa) upon laser activation. These findings suggest that ZnO@Fe3O4 NPs are promising candidates for combined photothermal therapy, magnetic-targeted drug delivery, and stimuli-responsive controlled release applications.

Magnetochemistry doi: 10.3390/magnetochemistry12010001

Authors: Tetyana Prokopiv Galina Gayda Roman Serkiz Viacheslav Zagorodnii Oleh Smutok Evgeny Katz Mykhailo Gonchar

There is a growing demand for biocompatible, non-toxic nanomaterials with specific functional properties, including catalytic activity. In this study, magnetic iron oxide nanoparticles were synthesized via chemical co-precipitation in the presence of polyethylene glycol (PEG). PEG was used as a coating agent to reduce particle agglomeration. Comprehensive characterization of the synthesized nanocomposites was performed using scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDX) and vibrating sample magnetometry (VSM). SEM studies confirmed the nanosized structure of the particles with an average diameter of 20–60 nm. The saturation magnetization values were 57.37 emu·g−1 for nFe3O4-PEG6000, 11.95 emu·g−1 for nFe3O4-PEG4000 and 3.97 emu·g−1 for nCo0.5Ni0.5Fe2O4-PEG4000. In addition to their high magnetic properties, ferrofluids exhibited peroxidase-like activity, which makes them highly suitable for bioanalytical and biomedical use. The Michaelis–Menten constant (KM) for hydrogen peroxide ranged from 1.15 to 4.98 mM. Transmission electron microscopy (TEM) proved the penetration of the nano-ferrofluids into the yeast cells of Ogataea polymorpha. The studied nano-ferrofluids were found to be non-toxic at concentrations up to 0.2 mg·mL−1 for both prokaryotic and eukaryotic cells, showing no inhibitory effect on the growth of the bacterium Escherichia coli, the yeast Ogataea polymorpha, or animal and human cell lines. These results indicate that the advantages of synthetic nano-ferrofluids—including peroxidase-like activity, strong magnetic properties, cost-effective synthesis, stability, and low toxicity—make the synthesized nano-ferrofluids highly promising for future biomedical and bioanalytical applications.

Magnetochemistry doi: 10.3390/magnetochemistry11120111

Authors: Nikolaos Maniotis Antonios Makridis

This study aims to identify optimal parameters for the clinical implementation of magnetic fields in therapeutic contexts, with a particular focus on in vitro magneto-mechanical actuation in biological systems. This approach relies on the transduction of magnetic energy into mechanical stress at low frequencies (<<100 Hz). Accordingly, the investigation centers on evaluating the magnetic field gradients responsible for initiating the motion of intracellular magnetic nanoparticles and the resulting mechanical forces acting upon them. To achieve this, a novel, custom-built, and highly adaptable three-dimensional turntable system was designed, calibrated, and implemented. This apparatus allows the generation of magnetic fields with precisely tunable amplitude and frequency, enabling controlled activation of magneto-mechanical mechanisms. In vitro experiments using this device facilitated the exposure of cancer cells to well-characterized magnetic fields, thereby inducing mechanical stimulation in the presence of nanoparticles distributed within intracellular or extracellular environments. Quantitative measurements of magnetic field intensities were performed, providing estimations of the forces exerted by magnetic nanoparticles with diverse physical characteristics (phase, size, and shape) under varying magnetic field gradients.

Magnetochemistry doi: 10.3390/magnetochemistry11120110

Authors: Jiawen Zhang Ning Luo Long Chao Nan Liu Zheng Lian Bin Liu Lijian Yang

Stress detection is an effective way to prevent pipeline failure, but stress recognition alone can hardly meet the safety and maintenance requirements of pipelines. Rather, improving the accuracy of stress detection and quantification has long been a top priority in the engineering sector. In the present study, stress detection models for pipelines were developed under varying magnetic excitation intensities, and the influence of a changing magnetic excitation field on stress recognition capacity was investigated. The variation law of the accuracy of stress detection under different excitation intensities was determined and validated experimentally. The results showed that at an excitation intensity of 2.5 of kA/m, the polarity of weak magnetic signals flipped when used to detect stress below 40 MPa, making the stress quantification difficult. The stress recognition capacity was the greatest under an excitation intensity of 7.5 kA/m for the stress below 40 MPa and the greatest under an excitation intensity of 5 kA/m for the stress of 40–160 MPa. Our research findings offer theoretical clues for choosing an appropriate excitation intensity for stress detection. The findings provide technical support for pipeline integrity assessment and risk warning, playing an important role in ensuring the safe operation of oil and gas transportation systems.

Magnetochemistry doi: 10.3390/magnetochemistry11120109

Authors: Fang Chen Yuchen Liu Qinkui Guo Yangjie Xiao Yuan Dong Sihan Yue Yichao Huang Zhenggui Li

A series of high-viscosity ferrofluids with variations in particle concentration and carrier liquid molecular weight were synthesized in a fluoroether oil base by the chemical coprecipitation method. The microstructure, surface coating, and magnetic properties of the nanoparticles were characterized, and the rheological properties of the corresponding ferrofluids were systematically investigated to elucidate their governing mechanisms and underlying mechanisms. The results indicate that the synthesized zinc-doped ferrite particles are spherical with a size of less than 50 nm and are chemically coated with a fluoroether acid. Moreover, the saturation magnetization of the ferrofluids increases with rising particle concentration. With the increase in particle concentration, the zero-field viscosity and shear stress of the ferrofluids increase significantly. The zero-field viscosity and shear yield stress of the ferrofluid increase significantly with the molecular weight of the carrier liquid, due to the strengthened entanglement of its molecular chains. At a carrier liquid molecular weight of 4600 g/mol, the 50 wt.% ferrofluid displayed a liquid character, in contrast to the gel-like character displayed by the 60 and 70 wt.% samples. The 60 wt.%-7480 g/mol sample demonstrated superior elasticity to its 60 wt.%-4600 g/mol counterpart. Furthermore, the application of a 100 mT magnetic field induced a transition from a liquid to a gel state in the 50 wt.%-4600 g/mol sample. This transition, driven by the formation of magnetic field-induced chain-like structures, significantly enhanced the magnetoviscous effect. This study provides the theoretical basis and experimental support for the development of high-viscosity ferrofluid sealing materials suitable for high-pressure, liquid environments and corrosive working conditions.

Magnetochemistry doi: 10.3390/magnetochemistry11120108

Authors: Rajat Kumar Yogesh Sharma Amit Kumar Goyal

Recent advancements in nanotechnology have intensified research efforts to address security concerns like hardware trojans and intellectual property (IP) piracy, particularly by exploring novel alternatives to traditional MOSFET devices. Spin-based devices, known for their low power consumption, non-volatility, and seamless integration with silicon substrates, have emerged as promising candidates. This research proposes a novel approach to enhance the security of integrated circuits using spin-based devices known as magnetic tunnel junctions (MTJs). A Non-volatile Polymorphic Logic (NPL) is optimized and designed to perform multiple operations, effectively concealing its true functionality. The analytical studies conducted on the Cadence Virtuoso platform using TSMC 65 nm MOS technology demonstrate the feasibility and efficacy of the proposed approach. The proposed NPL circuit enables polymorphism by allowing the circuit to perform all one- and two-input Boolean logic operations, including NOT, AND/NAND, OR/NOR, and XOR/XNOR, through adjustments of applied keys. This dynamic functionality makes it challenging for attackers to determine the circuit’s true operation. The proposed design exhibits similar timing characteristics for different logic operations, which further complicates the tampering attempts. Additionally, the circuit’s layout is designed to be symmetric, ensuring the execution of all possible operations by the same physical layout. This provides post-manufacturing security from reverse engineering and finds its applications in securing custom IC designs against the evolving landscape of hardware-based threats.

Magnetochemistry doi: 10.3390/magnetochemistry11120107

Authors: Andrew Pyataev Dilyara Kuzina Jérôme Gattacceca Carine Sadaka Razilia Muftakhetdinova

During their stay at the surface of the Earth, meteorites undergo terrestrial weathering. In particular, the iron-nickel alloys and iron sulfides that are abundant in many types of meteorites transform into oxides and oxihydroxides (magnetite, maghemite, akaganeite, etc.). Mössbauer spectroscopy is a powerful tool to identify these weathering products. However, distinguishing signals from different phases summed up in the Fe3+ paramagnetic doublets in the central part of the spectrum remains challenging. This study focuses on a detailed investigation of meteorite weathering products to separate signals from different secondary minerals formed on Earth in a series of weathered meteorites. We carried out a room-temperature Mössbauer spectroscopy study on seventy ordinary chondrites collected in the Atacama Desert, Chile, in order to make a comparative qualitative analysis of the mineralogy of their terrestrial weathering products. Based on these results, three samples showing a variety of weathering products (Catalina 146, Catalina 535, and El Médano 070) were selected for a detailed study and two of them for low-temperature Mössbauer study. We found that, above 200 K, most meteorites exhibit superparamagnetic magnetization dynamics attributable to strong dispersed maghemite–magnetite phase formed as a weathering product. On the other hand, other iron-bearing weathering products (goethite, akaganeite, hematite) demonstrate line shapes of the corresponding partial components that are close to the shapes of the bulk samples. Only two of the 70 measured meteorites showed no superparamagnetic behavior at room temperature.

Magnetochemistry doi: 10.3390/magnetochemistry11120106

Authors: Tian-Ge Zhai Jia-Meng Yuan Zhan-Bo Li Ding Ding Lei Xia

The magnetocaloric response of an amorphous Er69Ni31 alloy was studied in the present work. The eutectic Er69Ni31 alloy was successfully melt-spun into an amorphous ribbon. The formability and magnetocaloric performance of the Er69Ni31 amorphous alloy were studied. The amorphous sample exhibits good glass formability and a remarkable magnetocaloric effect with a magnetic entropy change peak of ~16.65 J/(kg × K) near 10 K under 5 Tesla. The magnetization and magnetocaloric behaviors were investigated to reveal the effect of spin-glass-like behaviors on the magnetocaloric response of the binary amorphous sample.

Magnetochemistry doi: 10.3390/magnetochemistry11120105

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

Magnetic flux leakage (MFL) testing is a widely used non-destructive method for detecting defects in ferromagnetic pipelines. However, demagnetizing fields in ferromagnetic materials can distort MFL signals, reducing detection accuracy. This study integrates demagnetizing components into the classical magnetic charge model using magnetic charge and dipole theories to assess the impact of demagnetization on MFL signals. The behavior of MFL signals under demagnetization, particularly for rectangular defects, is analytically characterized. The generation mechanism of the demagnetizing field is examined, and explicit expressions for triaxial demagnetizing components in cylindrical pipelines are derived. The effects of geometric parameters, such as inner and outer diameters and pipeline length, on demagnetizing components are systematically studied. The influence of demagnetization on MFL signal transmission is also explored. MFL scanning experiments on rectangular defects of different sizes validate the theoretical model, revealing that demagnetization attenuates the axial and radial components while enhancing the circumferential component. The proposed model improves prediction accuracy, reducing errors in the axial and radial components by 14.9% and enhancing the circumferential signal by 15%. Experimental MFL waveforms align closely with the model, confirming its validity and effectiveness.

Magnetochemistry doi: 10.3390/magnetochemistry11120104

Authors: Nozomi Tada Natsumi Yano Makoto Handa Yusuke Kataoka

Two diruthenium(II,II) naphthyridine complexes coordinated with 4-trifluoromethylbenzoate (O2CPh-4-CF3) and 3,5-bis(trifluoromethyl)benzoate (O2CPh-3,5-diCF3) ligands, formulated as [Ru2(npc)2(O2CPh-4-CF3)2] (4; npc = 1,8-naphthyridine-2-carboxylate) and [Ru2(npc)2(O2CPh-3,5-diCF3)2] (5), respectively, were synthesized and structurally characterized. Single-crystal X-ray diffraction analysis revealed that both 4 and 5 form a direct metal–metal bond between the two Ru ions (2.2893(8) and 2.2896(7) Å, respectively) and adopt a paddlewheel-type structure in which two npc and two trifluoromethyl-substituted benzoate ligands are coordinated to a Ru24+ core with a cis-2:2 arrangement. The temperature dependence of the magnetic susceptibility measurements of 4 and 5 exhibited very large zero-field splitting (D = 242 and 246 cm−1, respectively) of the triplet ground state of the Ru24+ core, similar to that of [Ru2(npc)2(O2CPh)2] (3; D = 238 cm−1). Owing to the effects of the trifluoromethyl substituents, compared with 3, 4 and 5 showed (i) a significant blue shift of the absorption bands in the visible region and (ii) a positive shift of the redox potentials, with both shifts becoming more pronounced as the number of trifluoromethyl substituents increased. These experimental results are in good agreement with the electronic structure results obtained from density functional theory calculations.

Magnetochemistry doi: 10.3390/magnetochemistry11120103

Authors: Petr Kharitonskii Andrei Krasilin Nadezhda Belskaya Svetlana Yanson Nikita Bobrov Andrey Ralin Kamil Gareev Nikita Zolotov Dmitry Zaytsev Elena Sergienko

A comprehensive study of the magnetic properties of baked clays containing ferrimagnetic particles in various magnetic states, including superparamagnetic, has been carried out in this work. The phase composition of the magnetic fraction of laboratory and industrial samples made from the same clay is mainly represented by iron (III) oxide polymorphs and possibly non-stoichiometric magnetite. Experimental methods included magnetic granulometry, Mössbauer spectroscopy, scanning electron microscopy, X-ray phase analysis, and pulsed electromagnetic measurements. A theoretical model of magnetostatically interacting particles with a lognormal volume distribution was used to interpret the experimental data, allowing the contribution of superparamagnetic grains to be taken into consideration. It is shown that the firing mode significantly affects the composition of iron oxide phases and their magnetic characteristics. Laboratory samples are characterized by approximately twice the proportion of superparamagnetic particles. At sufficiently low concentrations of ferrimagnet in samples <0.1%, the concentration of superparamagnetic particles is even two orders of magnitude lower. It is the use of pulse methods that provides a more reliable diagnosis of their presence. The complex application of experimental methods with theoretical modeling makes it possible to reveal and quantitatively describe the microheterogeneous nature of the magnetic state of baked clays, which is applicable to a wide range of magnetic materials, and to analyze more deeply the thermal and phase history of archaeological and geological objects.

Magnetochemistry doi: 10.3390/magnetochemistry11120102

Authors: Ye-Hui Qin Qian-Qian Su Song-Song Bao Li-Min Zheng

Lanthanide-based single-molecule magnets (Ln-SMMs) showing stimuli-responsive changes in photoluminescence (PL) and magnetic properties are attractive for their potential applications in information storage and molecular devices. In this work, we report two mononuclear complexes, namely, Dy(SCN)2(NO3)(Cl-depma)2(4-hpy)2 (Dy-Cl) and Dy(SCN)2(NO3)(Br-depma)2(4-hpy)2 (Dy-Br), where X-depma represents 10-X-9-diethylphosphinomethylanthracene (X = Cl, Br) and 4-hpy is 4-hydroxypyridine. Both contain face-to-face π-π-interacted anthracene rings and exhibit yellow-green excimer emission. Unlike the other related Dy–anthracene complexes without a halogen substituent, Dy-Cl and Dy-Br cannot undergo photocycloaddition reaction under UV-light irradiation. However, they exhibited remarkable grinding-induced changes in luminescence. Magnetic studies revealed that Dy-Cl and Dy-Br show SMM behavior under zero dc field with the effective energy barriers (Ueff/kB) of 259 K and 264 K, respectively. We also investigated the effect of pressure on the magnetic properties of Dy-Br and observed a reduction in the magnetization value, narrowing of the butterfly-shaped hysteresis loop, and acceleration of the magnetic relaxation under 1.09 GPa. The results demonstrate that introducing a halogen substituent into an anthracene group may pose significant influences on the photophysical and photochemical properties of the complexes. In addition, pressure may be a promising external stimulus to modulate the PL and SMM behaviors of Dy–anthracene complexes.

Magnetochemistry doi: 10.3390/magnetochemistry11110101

Authors: Zhihao Liao Xichun Zhong Xuan Huang Cuilan Liu Jiaohong Huang Dongling Jiao Raju V. Ramanujan

Rare earth-rich NaZn13-type La-Fe-Si-based alloys are promising candidates for near-room-temperature magnetocaloric applications. However, their poor corrosion resistance limits practical applications. The microstructure, corrosion behavior and magnetic entropy change of La0.8Ce0.2Fe9.2Co0.6Si1.2 alloys after annealing were systematically investigated. Annealing treatments were conducted at 1423 K for durations of 4–24 h. As annealing time increased, the α-Fe phase content decreased monotonically from ~7.81wt% to ~2.92wt%, accompanied by significant microstructural evolution. For the 4 h-annealed sample, extensive and large corroded spots were observed, attributed to micro-galvanic corrosion where the α-Fe phase (cathode) and 1:13 matrix phase (anode) formed active electrochemical pairs. Prolonged annealing reduced the corrosion current density by ~50%, directly correlating with the α-Fe phase reduction and improved microstructural homogeneity. Notably, corrosion exhibited a negligible effect on the magnetic entropy change of the alloys. This study confirms that optimizing annealing time to decrease α-Fe content and enhance microstructural uniformity represents an effective strategy to improve corrosion resistance without compromising magnetocaloric performance.

Magnetochemistry doi: 10.3390/magnetochemistry11110100

Authors: Pengfei Xu Jichang Zhang Jie Zeng Yulin Wang Xinyu Dou Yiling Fan Thomas Meersmann Chengbo Wang

Oxygen-enhanced magnetic resonance imaging (OE-MRI) enables non-invasive assessment of lung function by measuring longitudinal relaxation time (T1) changes induced by alternating inhalation of room air and pure oxygen. In this study, the pulmonary T1 and its reduction after breathing pure oxygen were quantified by using the free-breathing three-dimensional (3D) Look-Locker technique based on a stack-of-stars acquisition scheme. This method applied a continuous acquisition model to collect signals during both room-air and pure oxygen conditions without the need for breath-holding or respiratory gating. Comparative evaluations were conducted between the proposed 3D Look-Locker method and the conventional two-dimensional (2D) Look-Locker approach, using both phantom and in vivo experiments. The results demonstrate that the 3D technique yields more pronounced and reproducible T1 reductions between air and oxygen conditions compared to the 2D method. Additionally, the T1 of the average respiratory phase obtained by the 3D approach was compared with the T1 at end-expiration and end-inspiration measured by the 2D approach. A consistent decline in T1 across respiratory phases was demonstrated, from end-expiration to end-inspiration, as well as the average respiratory phase under free-breathing. These findings suggest that the proposed OE-MRI T1 measurement based on the 3D Look-Locker method provides a robust and clinically feasible approach for quantitative lung imaging.

Magnetochemistry doi: 10.3390/magnetochemistry11110099

Authors: Simona Gabriela Greculeasa Ovidiu Crișan

Efficient permanent magnets that are concomitantly economically viable are of paramount importance for allowing industrial stakeholders to maintain a growing and competitive advantage. This study provides a comprehensive overview of recent developments in the field of rare-earth-free nanocomposite permanent magnets based on hexaferrites. The basic phenomenology of exchange-spring-coupled nanocomposites, comprising hard and soft magnetic components, is thoroughly explained. The use of hexaferrites as a hard phase, serving as a viable alternative to rare-earth-based permanent magnets, is extensively discussed, taking economical, accessibility-related, and environmental aspects into consideration. State-of-the-Art architectures of hard–soft magnetic nanocomposites based on hexaferrites as the hard magnetic phase, ranging from typical nanocomposites to nanowire arrays and special core–shell-like morphologies, are explored in detail. The maximum energy product (BH)max, representing the quality indicator for permanent magnets, is investigated by taking into consideration various degrees of freedom, such as substitutions, geometry, size, shape, preparation, and processing conditions (annealing), volume fraction of magnetic phases, and interfaces. Promising strategies to overcome the present challenges (e.g., size control, coercivity–remanence trade-off, and optimization for large-scale production) are provided within the framework of future permanent magnet design.

Magnetochemistry doi: 10.3390/magnetochemistry11110098

Authors: Chao Wang Zheng Tan Dan Jia Xin Xin Li Meng Tao Liu Likui Ning Song Ma Enze Liu

In this study, a modified Curie–Weiss model was established for the magnetic susceptibility of high-purity molybdenum and Mo–La alloy powders. The elemental composition was analyzed by GDMS, and combined with the M–T and M–H data measured by SQUID, the temperature-independent contributions of weakly magnetic elements such as La and the paramagnetic contributions of impurity ions such as Fe, Co, and Ni were distinguished. Based on the parameters obtained from the nonlinear least squares fitting, the deviation between the magnetic susceptibility at room temperature calculated by the model and the experimental value was within 5%. The results show that this model can reasonably describe the influence of trace impurities on the magnetic susceptibility of the system and provides an effective method for the magnetic prediction of high-purity metal powders.

Magnetochemistry doi: 10.3390/magnetochemistry11110097

Authors: Ran Deng Min Sun Zhou Zhou Meng Zhou Lu Han Jiong Wang Yiyang Bai Limeng Peng Junyu Chen Guang Zhang Min Tang Zhong Zhang

This study systematically investigates the complex nonlinear rheological behavior of magnetorheological fluids (MRFs) and greases (MRGs) through comparative experiments under two shear modes (steady-state shear and large-amplitude oscillatory shear) at room temperature. Results demonstrate that during steady-state shear tests, the apparent viscosity of both materials decreases with the increasing shear rate, exhibiting shear-thinning behavior at high shear rates that aligns with the Herschel–Bulkley constitutive model. Throughout the logarithmically increasing shear rate range, the viscosity and shear stress of MRF consistently exceed those of MRG. Under low-frequency, large-amplitude oscillatory shear (LAOS) conditions, both materials display pronounced viscoelasticity and hysteresis. At higher current levels, the maximum shear stress of MRF surpasses MRG, but its hysteresis loops exhibit reduced smoothness. The Bouc–Wen model accurately characterizes the nonlinear hysteresis of both materials, with model parameters successfully identified via a genetic algorithm. This work establishes a universal framework for the dynamic mechanical response mechanisms of magnetorheological materials, providing theoretical guidance for designing and predicting the performance of smart damping devices.

Magnetochemistry doi: 10.3390/magnetochemistry11110096

Authors: Yue Bu Jianpeng Xu Chuanhua Li Zhixi Li Yongjing Yu Ziyong Yue

Sepsis-induced acute lung injury (SALI) is characterized by dysregulated inflammation with limited therapeutic options. Although Anemoside B4 (AB4) exhibits anti-inflammatory properties, its clinical application is hindered by poor bioavailability. To address this limitation, we developed magnetically guided gelatin microrobots (MG-AB4) for targeted AB4 delivery. The MG-AB4 system consists of a Fe3O4-loaded gelatin shell for enabling precise magnetic navigation (velocity: 110 μm/s), an AB4 core for rapid drug release which is advantageous for acute inflammatory responses, and surface modifications to enhance cellular uptake. Compared with free AB4, MG-AB4 significantly suppressed key inflammatory cytokines (Interleukin-6 (IL-6), Interleukin-1 beta (IL-1β), Tumor necrosis factor-alpha (TNF-α); p < 0.01), inhibited NF-κB activation (p < 0.01), and improved cell viability in an inflammatory model (p < 0.05). This study demonstrates that magnetically guided AB4 delivery using rapidly releasing microrobots is a promising strategy for SALI treatment, wherein the synergy of targeted delivery and potent anti-inflammatory action may effectively mitigate disease progression.

Magnetochemistry doi: 10.3390/magnetochemistry11110095

Authors: Shoujin Zhu Shuangjiu Feng Xiansong Liu Xucai Kan

Herein, we address the challenge of high core losses in soft magnetic composites (SMCs) at high frequencies by developing a FeSiAl/WS2 composite system processed under a transverse magnetic field (TMF). In this study, 200- and 600-mesh FeSiAl powders were used as base materials and combined with 2.25 wt.% two-dimensional tungsten disulfide (WS2; an insulating agent) to prepare FeSiAl/2.25 wt.%WS2 soft magnetic composites via ultrasonic mixing. The evolution of soft magnetic properties under a transverse magnetic field (TMF) was systematically investigated. The novelty of this work lies in the synergistic combination of fine FeSiAl particles and WS2 nanosheets as an interparticle insulator and the application of a TMF to simultaneously suppress eddy current and hysteresis losses—a challenge that is difficult to address using conventional approaches. Morphological analysis confirmed a uniform and continuous organic coating of WS2 nanosheets on FeSiAl particle surfaces. Permeability measurements revealed a slight decrease in effective permeability after the TMF treatment; however, the high-frequency performance was markedly enhanced. Magnetic loss analysis revealed a substantial reduction in the hysteresis loss and an increase in the quality factor under the TMF. Notably, the FeSiAl (600 mesh)/2.25 wt.% WS2 composite achieved a total magnetic loss of 234 kW/m3 under a TMF of 140 kA/m, magnetic induction of 20 mT, and frequency of 1 MHz, representing a 69% reduction compared with conventional SMCs. These results not only validate the effectiveness of the proposed synergistic approach but also highlight the potential of FeSiAl (600 mesh)/2.25 wt.% WS2 for use in high-power, high-frequency magnetic devices, with improved energy efficiency and thermal performance.

Magnetochemistry doi: 10.3390/magnetochemistry11110094

Authors: Maria J. S. Lima Fernando E. S. Silva Matheus D. Silva Kivia F. G. Araujo Marco A. Morales Uílame U. Gomes

In this work, we present the first report on the synthesis via the sol–gel method of a high-entropy (Fe0.2Co0.2Cu0.2Ni0.2Mn0.2)Nb2O6 with columbite–orthorhombic structure. Polyvinylpyrrolidone (PVP), ammonium niobium oxalate, and equimolar amounts of Fe, Co, Cu, Ni, and Mn ions were used. The refinement of the XRD pattern showed the presence of niobate crystallites with an average size of 48.4 nm and a fraction of 7.6 wt% of a spinel-like phase. At temperatures below 5 K, the DC and AC magnetometry results revealed the presence of a ferromagnetic-like phase due to the niobate phase. The Mössbauer spectrum at 300 K showed a paramagnetic and two magnetically ordered components corresponding to the niobate and the spinel-like phases, respectively. The spectral components were typical of Fe3+, indicating the presence of cation vacancies. The elemental mapping obtained from EDS measurements showed compositional homogeneity. The XRF measurements confirmed a composition consistent with nominal values. These results confirm the feasibility of synthesizing entropy-stabilized columbite oxides via the sol–gel route, opening new opportunities for the design of multifunctional ceramics with tunable structural and magnetic properties for high-performance thermal barrier coatings and energy conversion applications.

Magnetochemistry doi: 10.3390/magnetochemistry11110093

Authors: Cunhao Lu Fanjie Meng Jiajie Zhang Zeyuan Zhang

The magnitude of core loss is a crucial factor affecting the efficiency of power converters. Due to the complex mechanism of core loss, diverse influencing factors, and the strong coupling characteristics between materials and operating conditions, traditional core loss prediction models struggle to achieve high-precision prediction of core loss. Based on the Artificial Neural Network (ANN), this paper investigates core loss under high-frequency sinusoidal excitation. The core loss training data is processed using a logarithmic transformation method, and an ANN core loss prediction model is established with temperature, frequency, and magnetic flux density as features. The results show that, compared with non-logarithmic processing, logarithmic transformation of the data can effectively improve the prediction accuracy (PA) of the ANN model. Within the ±10% error range, the maximum PA of the ANN prediction model reaches 98.48%, and the minimum Mean Absolute Percentage Error (MAPE) can be as low as 2.58%. In addition, a comparison with the Steinmetz Equation (SE) and K-nearest neighbor (KNN) prediction models reveals that, for four materials, within the ±10% error range of the true core loss values, the minimum PA of the ANN model is 93.33% with an average of 95.38%; the minimum PA of the KNN model is 43.94% with an average of 62.07%; and the minimum PA of the SE model is 14.91% with an average of 19.83%. Furthermore, the MAPE of the ANN model is within 5%.

Magnetochemistry doi: 10.3390/magnetochemistry11110092

Authors: Hexiang Huang Dazhao Yu Hongjun Zhao Aiguo Gao Yanan Li Jiantao Qi

This study investigates the influence of magnetic fields on the electrochemical corrosion behavior of aerospace-grade H62 brass alloy in 3.5 wt% NaCl solution and its underlying 10 mechanisms. Employing electrochemical testing techniques combined with surface characterization methods, we explored the effects of magnetic field intensity (25–100 mT) and orientation (parallel and perpendicular to electrode surface) on the corrosion kinetics and corrosion product evolution of H62 brass alloy. Results demonstrate that magnetic fields significantly accelerate the corrosion process of H62 brass alloy. Under parallel magnetic field (100 mT), the corrosion current density increased from 0.49 μA/cm2 to 3.66 μA/cm2, approximately 7.5 times that of the non-magnetic condition, while perpendicular magnetic field increased it to 1.73 μA/cm2, approximately 3.5 times the baseline value. The charge transfer resistance decreased from 3382 Ω·cm2 to 1335 Ω·cm2. Magnetic field orientation determines the fundamental differences in corrosion acceleration mechanisms. Parallel magnetic fields primarily enhance mass transfer processes through Lorentz force-driven magnetohydrodynamic (MHD) effects, resulting in intensified uniform corrosion; perpendicular magnetic fields alter interfacial ion distribution through magnetic gradient forces, inducing localized corrosion tendencies. Magnetic fields promote the transformation of protective Cu2O films into porous Cu2(OH)3Cl, reducing the protective capability of corrosion product layers.

Magnetochemistry doi: 10.3390/magnetochemistry11110091

Authors: Song Hu Yapeng Zhang Bin Zhang

Magnetic nanoparticles (MNPs) perturb magnetic field homogeneity, influencing transverse relaxation and the full width at half maximum (FWHM) of nuclear magnetic resonance (NMR) spectra. In Nuclear Magnetic Resonance (NMR), this appears as decay of the free induction decay (FID) signal, whose relaxation rate determines spectral FWHM. In D2O containing MNPs, both nanoparticles and solvent molecules undergo Brownian motion and diffusion. Under a vertical main field (B0), MNPs respond to their magnetization behavior, evolving toward a dynamic steady state in which the time-averaged distribution of local field fluctuations remains stable. The resulting spatial magnetic field can thus characterize field homogeneity. Within this framework, Monte Carlo simulations of spatial field distributions approximate the dynamic environment experienced by nuclear spins. NMR experiments confirm that increasing MNP concentration and particle size significantly broadens FWHM, while stronger B0 enhances sensitivity to MNP-induced inhomogeneities.

Magnetochemistry doi: 10.3390/magnetochemistry11100090

Authors: Shan Qiu Tianle Zhang Xiaotong Han Jiahao Liu Liang Fang Yun Cheng

The skyrmion racetrack is a promising concept for future information technology. The primary issues with skyrmion racetrack memory are now error codes and Hall motion. Here, we propose a skyrmion pair racetrack memory. The Oersted fields generated by the non-contact current-carrying wire in the middle of the magnetic nanostrip stabilize the skyrmion pairs in the nanostrip, which are separated by a naturally formed domain wall. Through numerical models and micromagnetic simulations, we demonstrate that such a skyrmion pair can produce linear Hall motion along the nanostrip under the linear control of the Oersted field gradient. These findings offer a high-reliability method for skyrmion racetrack memory and a more efficient approach to designing devices that use the skyrmion Hall effect.

Magnetochemistry doi: 10.3390/magnetochemistry11100089

Authors: Xin Yu Yue Lv

Magnetic fields (MFs), including static (SMFs) and extremely low-frequency electromagnetic fields (ELF-EMFs), have recently emerged as potential modulators of anticancer drug responses. Evidence indicates that MFs can influence membrane transport, oxidative stress, DNA damage, apoptosis, and cell cycle regulation, thereby altering the efficacy of chemotherapeutics and targeted agents. These effects are strongly dependent on MFs’ parameters and biological context, leading to synergistic, antagonistic and no-effect outcomes. However, inconsistent exposure protocols, limited reproducibility, and scarce clinical validation remain major obstacles. This review highlights current experimental findings, proposes mechanistic links between MFs and drug action, and outlines key challenges for advancing MF-based adjuvant strategies in oncology.

Magnetochemistry doi: 10.3390/magnetochemistry11100088

Authors: Fateh Ali Mujahid Islam Farooq Ahmad Muhammad Usman Sana Ullah Asif

Background: The study of non-Newtonian fluids in thin channels is crucial for advancing technologies in microfluidic systems and targeted industrial coating processes. Nanofluids, which exhibit enhanced thermal properties, are of particular interest. This paper investigates the complex flow and heat transfer characteristics of a Sutterby nanofluid (SNF) within a thin channel, considering the combined effects of magnetohydrodynamics (MHD), Brownian motion, and bioconvection of microorganisms. Analyzing such systems is essential for optimizing design and performance in relevant engineering applications. Method: The governing non-linear partial differential equations (PDEs) for the flow, heat, concentration, and bioconvection are derived. Using lubrication theory and appropriate dimensionless variables, this system of PDEs is simplified into a more simplified system of ordinary differential equations (ODEs). The resulting nonlinear ODEs are solved numerically using the boundary value problem (BVP) Midrich method in Maple software to ensure accuracy. Furthermore, data for the Nusselt number, extracted from the numerical solutions, are used to train an artificial neural network (ANN) model based on the Levenberg–Marquardt algorithm. The performance and predictive capability of this ANN model are rigorously evaluated to confirm its robustness for capturing the system’s non-linear behavior. Results: The numerical solutions are analyzed to understand the variations in velocity, temperature, concentration, and microorganism profiles under the influence of various physical parameters. The results demonstrate that the non-Newtonian rheology of the Sutterby nanofluid is significantly influenced by Brownian motion, thermophoresis, bioconvection parameters, and magnetic field effects. The developed ANN model demonstrates strong predictive capability for the Nusselt number, validating its use for this complex system. These findings provide valuable insights for the design and optimization of microfluidic devices and specialized coating applications in industrial engineering.

Magnetochemistry doi: 10.3390/magnetochemistry11100087

Authors: Kaixuan Li Zhaoyang Wu

Soft magnetic materials have emerged as promising candidates due to their high power density in diverse magnetic components utilized for energy conversion, filtering, resonance, and isolation [...]

Magnetochemistry doi: 10.3390/magnetochemistry11100086

Authors: Alberto Tufaile Adriana Pedrosa Biscaia Tufaile

This study investigates the magneto-optical properties of a ferrofluid using an accessible Ferrocell device. Our findings demonstrate that the ferrofluid’s behavior is critically dependent on its concentration. At high concentrations, the medium is optically dense, with inter-particle scattering and absorption dominating, which prevents the formation of clear light patterns. However, with intermediate dilution, the system enters a “pattern formation zone” where the magnetic field effectively aligns the nanoparticles, creating complex, visible light patterns like horocycles. The appearance of these patterns provides evidence of field-induced ordering and structural coloration. The colors observed are not due to pigments, but result from the interaction of light with the periodic structures formed by the aligned nanoparticles. Our analysis, supported by the Mueller matrix framework, confirms that the ferrofluid acts as a retarder. The birefringence induced by the magnetic field varies across the film, leading to a chromatic dispersion that selectively suppresses certain wavelengths. This process explains how a specific color, such as blue, can be blocked at one location while others pass through, creating structural colors observed in the patterns.

Magnetochemistry doi: 10.3390/magnetochemistry11100085

Authors: Kun Fang Pei Li Hanbing Wang Xiangrui Huang Yihan Li

Gallic acid (GA) exhibits a broad range of biological activities; however, its clinical application is significantly limited by poor stability, rapid degradation, and low bioavailability. Consequently, developing responsive delivery platforms to enhance GA stability and targeted release has become an important research focus. Herein, GA was encapsulated within novel composite hydrogel beads (CMC-SA-Fe3O4@GA) prepared via crosslinking carboxymethyl chitosan (CMC) and sodium alginate (SA) with Fe3O4 nanoparticles (NPs) to facilitate efficient drug delivery. The formulation was characterized and evaluated in terms of drug-loading capacity, controlled-release properties, antioxidant activity, antibacterial performance, and biocompatibility. The results indicated that the GA loading efficiency reached 31.07 ± 1.23%. Application of an external magnetic field accelerated GA release, with the observed release kinetics fitting the Ritger–Peppas model. Furthermore, antioxidant capacity, evaluated by DPPH assays, demonstrated excellent antioxidant activity of the CMC-SA-Fe3O4@GA composite beads. Antibacterial tests confirmed sustained inhibitory effects against Escherichia coli and Staphylococcus aureus. In vitro, cellular assays indicated favorable biocompatibility with normal hepatic cells (HL-7702) and effective inhibition of hepatocellular carcinoma cells (HepG2). Overall, the novel pH- and magnetic field-responsive CMC-SA-Fe3O4@GA hydrogel system developed in this work offers considerable potential for controlled delivery of phenolic compounds, demonstrating promising applicability in biomedical and food-related fields.

Magnetochemistry doi: 10.3390/magnetochemistry11100084

Authors: Jia-Jun Song Xiao-Zhong Zuo En-Qi Zhu Qi-Guang Li Bao-Zhi Chen Ben-Wen Li

As a strong candidate for energy storage applications, Liquid Metal Batteries (LMBs) have the advantages of higher current density, longer cycle life, and simpler manufacturing of large-scale storage systems. Owing to the all-liquid construction, various kinds of Magnetohydrodynamic instabilities (MHDIs) are present in LMBs. In this paper, an in-depth study of the evolution process of MHDIs within LMBs has been conducted. By analyzing the characteristic velocity, the growth rate of instabilities γ has been defined so that the critical Hartmann number at which the instability occurs can be ascertained. A new critical parameter, mixed Reynolds number Remix, has been introduced to determine the duration of stable battery operation across varying charging/discharging currents, including those that may surpass the prescribed safe limits. Finally, a method for mitigating magnetohydrodynamic instability in LMBs through the configuration of busbar current is proposed, which can be seamlessly integrated with parallel battery packs. A comparative analysis of LMBs operation with/without bus current configuration reveals that when bus current is appropriately configured, the magnetic field strength within the battery undergoes a notable reduction of 40%, leading to a significant suppression of instability. The conclusions offer theoretical underpinnings for the application of LMBs in large-scale grid-level energy storage systems.

Magnetochemistry doi: 10.3390/magnetochemistry11100083

Authors: Wen Xiao Fuhao Sui Jiujiu Chen Hongbo Huang Tao Luo

We design a one-dimensional magnetoelastic phononic crystal slab composed of the smart magnetostrictive material Terfenol-D and pure tungsten. Band inversion and topological phase transitions are achieved by modifying the geometric parameters of the non-magnetic medium within the unit cell. The emergence of topological interface states within overlapping bandgaps, exhibiting distinct topological properties, along with their robustness against interfacial structural defects, is confirmed. The coupling effects between adjacent topological interface states in a sandwich-like supercell configuration are investigated, and their tunability under external magnetic fields is demonstrated. A Su-Schrieffer-Heeger (SSH) phononic crystal slab system under gradient magnetic fields is proposed. Critically, and in stark contrast to previous static or structurally graded designs, we achieve reconfigurable rainbow trapping of topological interface states solely by reprogramming the gradient magnetic field, leaving the physical structure entirely unchanged. This highly localized, compact, and broadband-tunable topological rainbow trapping system design holds significant promise for applications in elastic energy harvesting, wave filtering, and multi-frequency signal processing.

Magnetochemistry doi: 10.3390/magnetochemistry11100082

Authors: Jiayu Gu Lijuan Gui Dixin Yan Xunrong Xia Zhuoli Xie Le Xue

Tissue repair is a significant challenge in biomedical research. Traditional treatments face limitations such as donor shortage, high costs, and immune rejection. Recently, magnetic-responsive materials, particularly magnetic nanoparticles have been introduced into tissue engineering due to their ability to respond to external magnetic fields, generating electrical, thermal, and mechanical effects. These effects enable precise regulation of cellular behavior and promote tissue regeneration. Compared to traditional physical stimulation, magnetic-responsive material-mediated stimulation offers advantages such as non-invasiveness, deep tissue penetration, and high spatiotemporal precision. This review summarizes the classification, fabrication, magnetic effects and applications of magnetic-responsive materials, focusing on their mechanisms and therapeutic effects in neural and bone tissue engineering, and discusses future directions.

Magnetochemistry doi: 10.3390/magnetochemistry11090081

Authors: Alexey Chubarov

Magnetic nanoparticles and nanocomposites continue to garner considerable interest due to their versatility in biomedical applications, ranging from diagnostics and therapy to catalysis and sensing [...]

Magnetochemistry doi: 10.3390/magnetochemistry11090080

Authors: Garrett L. Wibbels Clementinah Oladun Tanner Y. O’Hara Isaiah Adelabu Joshua E. Robinson Firoz Ahmed Zachary T. Bender Anna Samoilenko Joseph Gyesi Larisa M. Kovtunova Oleg G. Salnikov Igor V. Koptyug Boyd M. Goodson W. Michael Snow Eduard Y. Chekmenev Roman V. Shchepin

Hyperpolarization (HP) techniques, such as Parahydrogen-Induced Polarization (PHIP), Signal Amplification by Reversible Exchange (SABRE), and dissolution Dynamic Nuclear Polarization (d-DNP), significantly enhance the sensitivity of nuclear magnetic resonance (NMR) spectroscopy for chemical analysis and metabolic imaging. However, the high cost of equipment, ranging from tens of thousands to millions of dollars, limits accessibility of hyperpolarization for the broad scientific community. In this work, we aim to mitigate some of the challenges by developing a cost-effective solution for parahydrogen (pH2)-based PHIP and SABRE HP methods. A custom coil-winding machine was designed to fabricate solenoid magnet coils, which were then evaluated for their magnetic field profiles, demonstrating a high degree of magnetic field homogeneity. A model 1H SABRE experiment successfully implemented the constructed solenoid, achieving efficient hyperpolarization. Additionally, the solenoid magnet can be utilized for in situ detection of hyperpolarization when integrated with a low-field NMR spectrometer, reducing the total setup cost to a few thousand dollars. These findings suggest that our approach makes HP technology more affordable and accessible, potentially broadening its applications in chemical and biomedical research, as well as educational settings involving undergraduate student researchers. This work provides a practical pathway to lower the financial barriers associated with pH2 HP setups.

Magnetochemistry doi: 10.3390/magnetochemistry11090079

Authors: Xiaoli Zhou Zengxin Li Xue Ni Wanhui Liu Lihui Yin

We developed a solvent-suppressed 1H nuclear magnetic resonance (NMR) method for the quantitative analysis of the components of rotigotine prolonged-release microspheres prepared for injection. Dimethyl terephthalate was used as an internal standard and dimethylsulfoxide -d6 as the solvent. The analysis was performed using a Bruker Avance III HD 600 MHz NMR spectrometer, employing the noesygppr1d pulse sequence at a controlled temperature of 25 °C. Nuclear magnetic resonance spectra were acquired with a relaxation delay time (D1) of 40 s to simultaneously determine the content of rotigotine and the excipients mannitol and stearic acid in the rotigotine prolonged-release microspheres. Using the proposed approach, we successfully quantified the active pharmaceutical ingredient rotigotine and excipients in the prolonged-release microspheres. This method demonstrated excellent linearity, high precision, and strong repeatability. The solvent-suppressed 1H NMR method developed in this study allows for the simultaneous quantification of rotigotine and the key excipients mannitol and stearic acid in the prolonged-release microspheres. This approach is accurate, simple, efficient, and environmentally friendly.

Magnetochemistry doi: 10.3390/magnetochemistry11090078

Authors: Aida Miranda Israel Betancourt

The microstructure and magnetic properties of rare-earth-free, melt-spun Co74Zr16Mo4Si3B3 alloys were investigated to enhance their hard magnetic response and elucidate their coercivity mechanism. The alloys exhibit a polycrystalline microstructure composed of randomly oriented, equiaxed grains, predominantly comprising the rhombohedral hard magnetic Co11Zr2 phase (92.4 wt.%). These materials display a favorable combination of magnetic properties, with coercive fields up to 581 kA/m, maximum magnetization reaching 0.30 T, and Curie temperatures as high as 751 K. An interpretation of the results, based on microstructural features, intrinsic magnetic parameters, and micromagnetic simulations, indicates that the coercivity mechanism of these melt-spun alloys can be attributed to the nucleation of reverse magnetic domains.

Magnetochemistry doi: 10.3390/magnetochemistry11090077

Authors: Xiaoshuang Gou Xinyu Sun Peng Cheng Wei Shi

The magnetic properties of molecular nanomagnets can be finely modulated by light, which provides great potential in optical switches, smart sensors, and data storage devices. Light-induced spin transition, structure changes, and radical formation could tune the static and dynamic magnetic properties of molecular nanomagnets with high spatial and temporal resolutions. Herein, we summarize the design strategies of photoresponsive molecular nanomagnets and review the recent advances in transition metal/lanthanide molecular nanomagnets with photomagnetic properties. The photoresponsive mechanism based on spin transition, photocyclization, and photogenerated radicals is discussed in detail, providing insights into the photomagnetic properties of molecular nanomagnets for advanced photoresponsive materials.

Magnetochemistry doi: 10.3390/magnetochemistry11090076

Authors: Wei Ding Huaili Zheng

The application of magnetism in water treatment processes has enhanced efficiency across various stages, including coagulation, flocculation, sedimentation, and filtration, representing a field with significant potential [...]

Magnetochemistry doi: 10.3390/magnetochemistry11090075

Authors: Xirong Wang Shijia Qin Xiulan Li Wenjing Zuo Qinglun Wang Licun Li Yue Ma Jinkui Tang Bin Zhao

A centrosymmetric dinuclear complex, [Dy2(H2dapp)2(μ-OH)2(H2O)2]·4TCNQ·2CH3OH, was synthesized using the TCNQ·− radical anion (TCNQ = 7,7,8,8-tetracyanoquino-dimethane) and pentadentate nitrogen-containing Schiff base ligand (H2dapp = 2,6-diacetylpyridine)-bis(2-pyridylhydrazone). In the Dy2 dimer, the two DyIII ions adopt eight-coordinated geometries intermediate between D4d and D2d symmetries, linked by two OH− groups, with ferromagnetic Dy-Dy interactions. The TCNQ·− radical anions are uncoordinated, and they pack tightly into antiparamagnetic dimers to balance the system charge. Under zero field, weak magnetic relaxation was observed, with an approximate Δeff = 2.82 K and τ0 = 6.88 × 10−6 s. This might be attributed to the short intermolecular Dy···Dy distance of 7.97 Å, which could enhance intermolecular dipolar interactions and quantum tunneling of magnetization (QTM).

Magnetochemistry doi: 10.3390/magnetochemistry11090074

Authors: Cristian E. Botez Zachary Musslewhite

We investigated the effects of chemical and physical changes on the interplay between the Néel and Brown superspin relaxation mechanisms in ferrofluids containing 18 nm-diameter Co0.2Fe2.8O4 magnetic nanoparticles. We attempted to tune the ferrofluid’s magnetization dynamics via three methods: (i) changing the carrier fluid from Isopar M to kerosene (ii) doubling the Co-doping level from x = 0.2 to x = 0.4, and (iii) diluting the Co0.2Fe2.8O4/Isopar M nanomagnetic fluid from δ = 1 mg/mL to δ = 0.1 mg/mL. We used temperature-resolved ac-susceptibility measurements at different frequencies, χ″ vs. T|f, to gain insight into the thermally driven superspin dynamics of the nanoparticles within the ferrofluid. Our data demonstrates that both increasing x and using a different carrier fluid quantitatively alter the temperature dependence of the Néel and Brown relaxation frequency (fN vs. T and fB vs. T) by changing the nanoparticles’ magnetic moments and the fluid’s viscosity. Yet, the two mechanisms remain decoupled, as indicated by the presence of two magnetic events (peaks in the χ″ vs. T|f datasets) one corresponding to the Néel and the other to Brown relaxation. On the other hand, diluting the ferrofluid leads to a qualitative change in the collective superspin dynamics behavior. Indeed, there is just one χ″-peak in the data from the δ = 0.1 mg/mL nanofluid, and its f vs. T dependence is well-described by a model that includes coupled contributions from both the Néel and Brown relaxation: fT=p·Tγ0·exp−E′kBT−T0′+  (1 − p) f0exp−EBkBT−T0. This is a remarkable behavior that demonstrates the ability to control a ferrofluids magnetization dynamics through simple chemical and physical changes.

Magnetochemistry doi: 10.3390/magnetochemistry11090073

Authors: Limin Zhou Hongling Lv Yuning Liang Dongcheng Liu Zaiheng Yao Shuchang Luo Zilu Chen

To develop single molecule magnets, a dinuclear complex [Dy2(HOBQ)4Cl6] (1) was prepared from the reaction of DyCl3 with benzo[h]quinolin-10-ol (HOBQ). Each Dy(III) ion shows a compressed octahedral geometry and the two Dy(III) ions in 1 are bridged by two Cl− ligands to construct a dinuclear structure with the four HOBQ ligands on the axial positions and six Cl− ligands in the equatorial plane. Magnetic measurements showed that complex 1 is a field-induced single molecule magnet having an obvious magnetic hysteresis loop with an energy barrier of 71(2) K. These experimental results are corroborated by the ab initio complete active space self-consistent field (CASSCF) calculations which also interpret the magneto-structural correlation. It is a typical example to achieve Dy(III) SMM through regulating coordination geometry, i.e., lengthening equatorial coordination bonds and shortening axial ones to form a compressed octahedral geometry.

Magnetochemistry doi: 10.3390/magnetochemistry11090072

Authors: Elena V. Fomenko Yuriy V. Knyazev Galina V. Akimochkina Sergey V. Semenov Vladimir V. Yumashev Leonid A. Solovyov Natalia N. Anshits Oleg A. Bayukov Alexander G. Anshits

High-calcium fly ash (HCFA), produced from the lignite combustion, has emerged as a global concern due to its fine particle size and adverse environmental impacts. This study presents the characteristics of dispersed microspheres from HCFA obtained using modern techniques, such as XRD, SEM-EDS, 57Fe Mössbauer spectroscopy, DSC-TG, particle size analysis, and magnetic measurements. It is found that an increase in microsphere size is likely due to the growth of the silicate glass-like phase, while the magnetic crystalline phase content remains stable. According to the 57Fe Mössbauer spectroscopy, there are two substituted Ca-based ferrites—CaFe2O4 and Ca2Fe2O5 with a quite different magnetic behavior. Besides, the magnetic ordering temperature of the brownmillerite (Ca2Fe2O5) phase increases with the average diameter of the microspheres. FORC analysis reveals enhanced magnetic interactions as microsphere size increases, indicating an elevation in the concentration of magnetic microparticles, primarily on the microsphere surface, as supported by electron microscopy data. The discovered the magnetic crystallographic phases distribution on the microsphere’s surface claims the accessibility for further enrichment of the magnetically active particles and the possible application of fly ashes as a cheap source for magnetic materials synthesis.

Magnetochemistry doi: 10.3390/magnetochemistry11090071

Authors: Xiaotian Wang Yan Zhuang Kinjal J. Shah Yongjun Sun

Wastewater containing heavy metals can come from a variety of sources and is extremely toxic and hard to break down. Conventional treatment methods can easily result in secondary pollution and are expensive. The research on magnetic chitosan composites, a new adsorbent in the treatment of heavy metal wastewater, is methodically reviewed in this paper. It offers a theoretical foundation for the creation of more environmentally friendly and effective wastewater treatment technology by examining its preparation and modification technology, adsorption mechanism, and application performance. This paper provides a summary of the technology used to prepare and modify magnetic chitosan composites. Both the cross-linking and co-precipitation methods are thoroughly examined. A summary of the fundamental process of heavy metal ion adsorption is provided, along with information on the chemical and physical impacts. Of these, chemical adsorption has been shown to work well with the majority of heavy metal adsorption systems. According to application research, magnetic chitosan exhibits good adaptability in real-world industrial wastewater treatment and has outstanding adsorption performance for various heavy metal ion types and multi-metal coexistence systems (including synergistic/competitive effects). Lastly, the optimization of the material preparation and modification process, the mechanism influencing the various coexisting ion types, and the improvement of regeneration ability should be the main areas of future development.