Magnetochemistry

16 pages, 9291 KB

Open AccessArticle

Improved Corrosion Resistance of La_0.8Ce_0.2Fe_9.2Co_0.6Si_1.2 Magnetocaloric Alloys for Near-Room-Temperature Applications

by Zhihao Liao, Xichun Zhong, Xuan Huang, Cuilan Liu, Jiaohong Huang, Dongling Jiao and Raju V. Ramanujan

Magnetochemistry 2025, 11(11), 101; https://doi.org/10.3390/magnetochemistry11110101 - 18 Nov 2025

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Abstract

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 La_0.8Ce_0.2Fe_9.2Co_0.6Si_1.2 alloys after [...] Read more.

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 La_0.8Ce_0.2Fe_9.2Co_0.6Si_1.2 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. Full article

(This article belongs to the Special Issue Advance of Magnetocaloric Effect and Materials)

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17 pages, 3868 KB

Open AccessArticle

Three-Dimensional Look-Locker Method for Free-Breathing T1 Mapping of Oxygen-Enhanced Pulmonary Magnetic Resonance Imaging

by Pengfei Xu, Jichang Zhang, Jie Zeng, Yulin Wang, Xinyu Dou, Yiling Fan, Thomas Meersmann and Chengbo Wang

Magnetochemistry 2025, 11(11), 100; https://doi.org/10.3390/magnetochemistry11110100 - 18 Nov 2025

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Abstract

Oxygen-enhanced magnetic resonance imaging (OE-MRI) enables non-invasive assessment of lung function by measuring longitudinal relaxation time (

T_{1}

) changes induced by alternating inhalation of room air and pure oxygen. In this study, the pulmonary

T_{1}

and its reduction after breathing [...] Read more.

Oxygen-enhanced magnetic resonance imaging (OE-MRI) enables non-invasive assessment of lung function by measuring longitudinal relaxation time (

T_{1}

) changes induced by alternating inhalation of room air and pure oxygen. In this study, the pulmonary

T_{1}

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

T_{1}

reductions between air and oxygen conditions compared to the 2D method. Additionally, the

T_{1}

of the average respiratory phase obtained by the 3D approach was compared with the

T_{1}

at end-expiration and end-inspiration measured by the 2D approach. A consistent decline in

T_{1}

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

T_{1}

measurement based on the 3D Look-Locker method provides a robust and clinically feasible approach for quantitative lung imaging. Full article

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22 pages, 5584 KB

Open AccessReview

Rare-Earth-Free Exchange-Coupled Nanocomposites Based on M-Type Hexaferrites

by Simona Gabriela Greculeasa and Ovidiu Crișan

Magnetochemistry 2025, 11(11), 99; https://doi.org/10.3390/magnetochemistry11110099 - 11 Nov 2025

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Abstract

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. [...] Read more.

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. Full article

(This article belongs to the Special Issue Fine Tuning of Magnetic Iron Oxide Nanostructures)

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12 pages, 1294 KB

Open AccessArticle

Magnetic Susceptibility of High-Purity Molybdenum: Role of Trace Impurities and Theoretical Modeling

by Chao Wang, Zheng Tan, Dan Jia, Xin Xin, Li Meng, Tao Liu, Likui Ning, Song Ma and Enze Liu

Magnetochemistry 2025, 11(11), 98; https://doi.org/10.3390/magnetochemistry11110098 - 11 Nov 2025

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Abstract

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 [...] Read more.

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. Full article

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14 pages, 2678 KB

Open AccessArticle

Modeling and Experimental Investigation on Rheological Characteristics of Magnetorheological Fluids and Greases Under Steady and Large-Amplitude Oscillatory Shear

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

Magnetochemistry 2025, 11(11), 97; https://doi.org/10.3390/magnetochemistry11110097 - 6 Nov 2025

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Abstract

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 [...] Read more.

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. Full article

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16 pages, 4260 KB

Open AccessArticle

Programmable Magnetic Navigation of Gelatin Microrobots Enhances AB4 Delivery to Inflamed Lung Epithelium

by Yue Bu, Jianpeng Xu, Chuanhua Li, Zhixi Li, Yongjing Yu and Ziyong Yue

Magnetochemistry 2025, 11(11), 96; https://doi.org/10.3390/magnetochemistry11110096 - 1 Nov 2025

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Abstract

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 [...] Read more.

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. Full article

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11 pages, 1821 KB

Open AccessArticle

Enhancing the High-Frequency Performance of FeSiAl/2.25 wt.% WS₂ Composites Through the Application of a Transverse Magnetic Field

by Shoujin Zhu, Shuangjiu Feng, Xiansong Liu and Xucai Kan

Magnetochemistry 2025, 11(11), 95; https://doi.org/10.3390/magnetochemistry11110095 - 29 Oct 2025

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Abstract

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 [...] Read more.

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. Full article

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14 pages, 2209 KB

Open AccessArticle

Synthesis, Structural, and Magnetic Properties of High-Entropy (Fe_0.2Co_0.2Cu_0.2Ni_0.2Mn_0.2)Nb₂O₆

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

Magnetochemistry 2025, 11(11), 94; https://doi.org/10.3390/magnetochemistry11110094 - 28 Oct 2025

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Abstract

In this work, we present the first report on the synthesis via the sol–gel method of a high-entropy (Fe_0.2Co_0.2Cu_0.2Ni_0.2Mn_0.2)Nb₂O₆ with columbite–orthorhombic structure. Polyvinylpyrrolidone (PVP), ammonium niobium oxalate, and equimolar amounts [...] Read more.

In this work, we present the first report on the synthesis via the sol–gel method of a high-entropy (Fe_0.2Co_0.2Cu_0.2Ni_0.2Mn_0.2)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. Full article

(This article belongs to the Special Issue Magnetic Materials and Composites: Synthesis, Properties, and Applications)

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16 pages, 2248 KB

Open AccessArticle

Core Loss Prediction Model of High-Frequency Sinusoidal Excitation Based on Artificial Neural Network

by Cunhao Lu, Fanjie Meng, Jiajie Zhang and Zeyuan Zhang

Magnetochemistry 2025, 11(11), 93; https://doi.org/10.3390/magnetochemistry11110093 - 25 Oct 2025

Viewed by 565

Abstract

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 [...] Read more.

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%. Full article

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16 pages, 17336 KB

Open AccessArticle

Effect of Magnetic Field on Electrochemical Corrosion Behavior of H62 Brass Alloy

by Hexiang Huang, Dazhao Yu, Hongjun Zhao, Aiguo Gao, Yanan Li and Jiantao Qi

Magnetochemistry 2025, 11(11), 92; https://doi.org/10.3390/magnetochemistry11110092 - 24 Oct 2025

Viewed by 596

Abstract

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 [...] Read more.

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. Full article

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17 pages, 1816 KB

Open AccessArticle

Investigating Magnetic Nanoparticle–Induced Field Inhomogeneity via Monte Carlo Simulation and NMR Spectroscopy

by Song Hu, Yapeng Zhang and Bin Zhang

Magnetochemistry 2025, 11(11), 91; https://doi.org/10.3390/magnetochemistry11110091 - 23 Oct 2025

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Abstract

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 [...] Read more.

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 (

B_{0}

), 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

B_{0}

enhances sensitivity to MNP-induced inhomogeneities. Full article

(This article belongs to the Section Magnetic Nanospecies)

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Magnetochemistry, Volume 11, Issue 11 (November 2025) – 11 articles

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