Pub Date : 2026-03-15Epub Date: 2026-01-29DOI: 10.1016/j.jmmm.2026.173884
Kailun Ji , Longhui Xiong , Wei Yuan , Ping Wang , Jianjun Qu , Pan Liu
Quantitative assessment of White Etching Layer (WEL) thickness in rails is essential for proactive railway maintenance. We develop an inversion model that correlates Magnetic Flux Leakage (MFL) signal features with WEL thickness by analyzing the physical relationship between martensite-induced permeability variations and characteristic bipolar MFL signals. To bridge the simulation-experiment gap, we implement a transfer learning strategy combining simulation-based pre-training with fine-tuning on limited experimental data. The method constructs a parametric sample library via finite element simulations, extracts key MFL features (peak-to-peak value, peak distance, waveform asymmetry), and fine-tunes the model using metallographically validated field samples. Field tests demonstrate a mean absolute error of 19.0 μm and an 87.5% detection rate for WEL thickness prediction. This work provides a practical solution for quantitative microstructure assessment in nondestructive testing applications with scarce labeled data.
{"title":"A magnetic flux leakage inversion model for rail white etching layer thickness integrating physical mechanism and data-driven approaches","authors":"Kailun Ji , Longhui Xiong , Wei Yuan , Ping Wang , Jianjun Qu , Pan Liu","doi":"10.1016/j.jmmm.2026.173884","DOIUrl":"10.1016/j.jmmm.2026.173884","url":null,"abstract":"<div><div>Quantitative assessment of White Etching Layer (WEL) thickness in rails is essential for proactive railway maintenance. We develop an inversion model that correlates Magnetic Flux Leakage (MFL) signal features with WEL thickness by analyzing the physical relationship between martensite-induced permeability variations and characteristic bipolar MFL signals. To bridge the simulation-experiment gap, we implement a transfer learning strategy combining simulation-based pre-training with fine-tuning on limited experimental data. The method constructs a parametric sample library via finite element simulations, extracts key MFL features (peak-to-peak value, peak distance, waveform asymmetry), and fine-tunes the model using metallographically validated field samples. Field tests demonstrate a mean absolute error of 19.0 μm and an 87.5% detection rate for WEL thickness prediction. This work provides a practical solution for quantitative microstructure assessment in nondestructive testing applications with scarce labeled data.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"642 ","pages":"Article 173884"},"PeriodicalIF":3.0,"publicationDate":"2026-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146185804","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-15Epub Date: 2026-02-06DOI: 10.1016/j.jmmm.2026.173904
Yulia E. Samoshkina , Dmitriy S. Neznakhin , Valeriya V. Govorina , Igor E. Korsakov
The magnetic and magnetocaloric properties of epitaxial La1-хKхMnO3 thin films (where K is a monovalent cation and x = 0.05–0.18), synthesized via a two-step process involving metal-organic chemical vapor deposition followed by isopiestic annealing, are presented. The magnetic entropy change (ΔS) and relative cooling power (RCP) were systematically evaluated under applied magnetic fields of up to 5 T. The films exhibit at high magnetic fields a pronounced magnetocaloric effect within the temperature range of 130–270 K. The maximum ΔS reaches up to 3.34 J/kg·K, and the RCP up to 310.7 J/kg, depending on the doping level. In contrast to bulk counterparts, the thin films demonstrate reduced magnetocaloric parameters, although the observed values are comparable to those reported for Gd-based thin films. These results emphasize the potential of thin-film structures both for the fundamental investigation of low-dimensional magnetocaloric phenomena and for the integration of magnetocaloric-active materials into microscale solid-state cooling systems. Further refinement of synthesis conditions and film architecture is essential to enhance performance and enable practical applications.
{"title":"Synthesis and magnetocaloric properties of potassium-doped manganite films","authors":"Yulia E. Samoshkina , Dmitriy S. Neznakhin , Valeriya V. Govorina , Igor E. Korsakov","doi":"10.1016/j.jmmm.2026.173904","DOIUrl":"10.1016/j.jmmm.2026.173904","url":null,"abstract":"<div><div>The magnetic and magnetocaloric properties of epitaxial La<sub>1-х</sub>K<sub>х</sub>MnO<sub>3</sub> thin films (where K is a monovalent cation and <em>x</em> = 0.05–0.18), synthesized via a two-step process involving metal-organic chemical vapor deposition followed by isopiestic annealing, are presented. The magnetic entropy change (<em>ΔS</em>) and relative cooling power (<em>RCP</em>) were systematically evaluated under applied magnetic fields of up to 5 T. The films exhibit at high magnetic fields a pronounced magnetocaloric effect within the temperature range of 130–270 K. The maximum <em>ΔS</em> reaches up to 3.34 J/kg·K, and the <em>RCP</em> up to 310.7 J/kg, depending on the doping level. In contrast to bulk counterparts, the thin films demonstrate reduced magnetocaloric parameters, although the observed values are comparable to those reported for Gd-based thin films. These results emphasize the potential of thin-film structures both for the fundamental investigation of low-dimensional magnetocaloric phenomena and for the integration of magnetocaloric-active materials into microscale solid-state cooling systems. Further refinement of synthesis conditions and film architecture is essential to enhance performance and enable practical applications.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"642 ","pages":"Article 173904"},"PeriodicalIF":3.0,"publicationDate":"2026-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146185901","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The efficiency of magnetic fluid hyperthermia (MFH) critically depends on how the internal structure of magnetic nanoparticles (MNPs) governs their magnetic energy losses. In this work, we demonstrate that crystallite size is the important factor controlling heat generation in cobalt ferrite (CoFe₂O₄) MNPs. For this, two types of single-core (17 and 23 nm) and two types (39 and 57 nm) of multi-core CoFe2O4 MNPs were synthesized using thermal decomposition technique with surfactant-ratio control, followed by hydrophilization of MNPs with 3,4-dihydroxyhenylacetic acid. Under an alternating magnetic field (H = 20 kA·m−1, f = 393.1 kHz), the efficiency of heating colloidal solutions of MNPs was studied: 23 nm single-core cubes with the largest crystallites (∼28.4 nm) exhibited the highest specific absorption rate (SAR = 333 W·g−1) and normalized intrinsic loss power (ILP = 3.34 nH·m2·kg−1), while 57 nm multicore clusters composed of small crystallites (∼15.7 nm) demonstrate a relatively low value of 0.05 nH·m2·kg−1. Moreover, the heating efficiency improved with increasing crystallite size and passed through a maximum with increasing core size of the entire nanoparticle. We attribute this result to a transition from Néel relaxation in larger-crystallite, shape-anisotropic structures to magnetization dominated by domain-wall displacement in large, fine-crystallite multicore assemblies. These findings identify crystallite size as a decisive, yet underappreciated, descriptor for optimizing CoFe₂O₄ hyperthermia mediators.
{"title":"Morphology-dependent heat generation efficiency of cobalt ferrite nanoparticles for magnetic hyperthermia application","authors":"Anastasiia Prishchepa , Anna Ivanova , Polina Lazareva , Maxim Abakumov , Aleksey Nikitin","doi":"10.1016/j.jmmm.2026.173902","DOIUrl":"10.1016/j.jmmm.2026.173902","url":null,"abstract":"<div><div>The efficiency of magnetic fluid hyperthermia (MFH) critically depends on how the internal structure of magnetic nanoparticles (MNPs) governs their magnetic energy losses. In this work, we demonstrate that crystallite size is the important factor controlling heat generation in cobalt ferrite (CoFe₂O₄) MNPs. For this, two types of single-core (17 and 23 nm) and two types (39 and 57 nm) of multi-core CoFe<sub>2</sub>O<sub>4</sub> MNPs were synthesized using thermal decomposition technique with surfactant-ratio control, followed by hydrophilization of MNPs with 3,4-dihydroxyhenylacetic acid. Under an alternating magnetic field (<em>H</em> = 20 kA·m<sup>−1</sup>, <em>f</em> = 393.1 kHz), the efficiency of heating colloidal solutions of MNPs was studied: 23 nm single-core cubes with the largest crystallites (∼28.4 nm) exhibited the highest specific absorption rate (SAR = 333 W·g<sup>−1</sup>) and normalized intrinsic loss power (ILP = 3.34 nH·m<sup>2</sup>·kg<sup>−1</sup>), while 57 nm multicore clusters composed of small crystallites (∼15.7 nm) demonstrate a relatively low value of 0.05 nH·m<sup>2</sup>·kg<sup>−1</sup>. Moreover, the heating efficiency improved with increasing crystallite size and passed through a maximum with increasing core size of the entire nanoparticle. We attribute this result to a transition from Néel relaxation in larger-crystallite, shape-anisotropic structures to magnetization dominated by domain-wall displacement in large, fine-crystallite multicore assemblies. These findings identify crystallite size as a decisive, yet underappreciated, descriptor for optimizing CoFe₂O₄ hyperthermia mediators.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"642 ","pages":"Article 173902"},"PeriodicalIF":3.0,"publicationDate":"2026-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146185906","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-15Epub Date: 2026-01-26DOI: 10.1016/j.jmmm.2026.173876
Q. Liu, Y. Li, S. Bai, H. Song, X. Wang, Q. Zhang, S. Fu, Xuan-Zhang Wang
The magic dispersion of ghost surface polaritons (GSPs) is theoretically shown in an antiferromagnetic film (AFF) surrounded by a medium. GSP dispersion curves rarely intersect in the space and are highly sensitive to the AFF thickness and permittivity of outside medium. Each intersection corresponds to two different GSP modes or degenerate states, resembling exception points in non-Hermitian systems. This degeneracy is unique to this type of surface polariton. The film-thickness-dependence of GSP reflects its oscillatory behavior and the outside-medium-dependence of GSP demonstrates that it exists in a finite interval of outside permittivity. The numerical simulations of attenuated total reflection technique prove that the degenerate phenomenon and modes of GSP are observable in experiment.
{"title":"Unique dispersion and degenerate states of ghost surface polariton in antiferromagnetic film","authors":"Q. Liu, Y. Li, S. Bai, H. Song, X. Wang, Q. Zhang, S. Fu, Xuan-Zhang Wang","doi":"10.1016/j.jmmm.2026.173876","DOIUrl":"10.1016/j.jmmm.2026.173876","url":null,"abstract":"<div><div>The magic dispersion of ghost surface polaritons (GSPs) is theoretically shown in an antiferromagnetic film (AFF) surrounded by a medium. GSP dispersion curves rarely intersect in the <span><math><mi>ω</mi><mo>−</mo><mi>k</mi></math></span> space and are highly sensitive to the AFF thickness and permittivity of outside medium. Each intersection corresponds to two different GSP modes or degenerate states, resembling exception points in non-Hermitian systems. This degeneracy is unique to this type of surface polariton. The film-thickness-dependence of GSP reflects its oscillatory behavior and the outside-medium-dependence of GSP demonstrates that it exists in a finite interval of outside permittivity. The numerical simulations of attenuated total reflection technique prove that the degenerate phenomenon and modes of GSP are observable in experiment.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"642 ","pages":"Article 173876"},"PeriodicalIF":3.0,"publicationDate":"2026-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146185908","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-15Epub Date: 2026-01-31DOI: 10.1016/j.jmmm.2026.173874
U. Mohanty , S.D. Kaushik , B. Dhal , I. Naik
The polycrystalline MnTi1-xFexO3 with x = 0.01, 0.02, 0.03, 0.04 and 0.05 were prepared by solid state reaction method and obtained Ilmenite structure of hexagonal symmetry with space group R from Rietveld refinement of room temperature X-ray diffraction. In order to reveal the materials disorder/defects, the materials surface morphology and its elementary identification in atomic weight percentage were investigated through SEM and EDX data respectively. Then XPS data were analysed for the valence state of Mn, Ti and Fe ions to elucidate the low temperature experimental magnetic behaviour. Using these, the temperature dependent dc magnetization has been explained by Curie-Weiss law and normalized susceptibility which implies long-range interactions with canted-spin. Subsequently, M(H) behaviour is taken in to consideration and confirmed the existence of spin reorientation (SR) with possible spin-glass like features at low temperatures in these materials.
{"title":"Spin-reorientation and magnetic anisotropy in ilmenite MnTi(Fe)O3 system","authors":"U. Mohanty , S.D. Kaushik , B. Dhal , I. Naik","doi":"10.1016/j.jmmm.2026.173874","DOIUrl":"10.1016/j.jmmm.2026.173874","url":null,"abstract":"<div><div>The polycrystalline MnTi<sub>1-x</sub>Fe<sub>x</sub>O<sub>3</sub> with x = 0.01, 0.02, 0.03, 0.04 and 0.05 were prepared by solid state reaction method and obtained Ilmenite structure of hexagonal symmetry with space group R<span><math><mover><mn>3</mn><mo>¯</mo></mover></math></span> from Rietveld refinement of room temperature X-ray diffraction. In order to reveal the materials disorder/defects, the materials surface morphology and its elementary identification in atomic weight percentage were investigated through SEM and EDX data respectively. Then XPS data were analysed for the valence state of Mn, Ti and Fe ions to elucidate the low temperature experimental magnetic behaviour. Using these, the temperature dependent dc magnetization has been explained by Curie-Weiss law and normalized susceptibility which implies long-range interactions with canted-spin. Subsequently, M(H) behaviour is taken in to consideration and confirmed the existence of spin reorientation (SR) with possible spin-glass like features at low temperatures in these materials.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"642 ","pages":"Article 173874"},"PeriodicalIF":3.0,"publicationDate":"2026-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146185933","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-15Epub Date: 2026-01-29DOI: 10.1016/j.jmmm.2026.173886
Xiaoli Gong , Mahdi Feizpour , Yikun Zhang , Touradj Ebadzadeh , Lingwei Li
The magnetocaloric (MC) performances in many rare-earth (RE)-dominated ceramics have been extensively explored in the search for suitable candidates for cryogenic magnetic refrigeration (MR) applications. Herein, a single-phased Gd6WO12 ceramic was synthesized via a solid-state route, and its crystal structure, elemental valence states, magnetic phase transition (MPT), and cryogenic MC properties were systematically investigated. The results showed that the Gd6WO12 crystallizes in a trigonal R-3 structure and exhibits antiferromagnetic ordering at the Néel temperature of 2.9 K. The constituent elements are homogeneously distributed and adopt the expected valence states of Gd3+, W6+, and O2−. A considerable and reversible cryogenic MC effect in antiferromagnetic Gd6WO12 was observed which is associated with its field-induced first-order MPT. The MC parameters of maximum magnetic entropy change/temperature-averaged entropy change and relative cooling power/refrigerant capacity (magnetic-field change = 0–7 T) of Gd6WO12 ceramic are determined as 21.7/19.7 J·kg−1·K−1 and 193.9/256.8 J·kg−1, respectively. These values are surpassing those of RE6MoO12 ceramics and comparable to some recently reported high-performance RE-dominated MC materials, indicating that the antiferromagnetic Gd6WO12 ceramic could be a considerable candidate material for cryogenic refrigeration applications.
{"title":"Revealing the cryogenic magnetic properties and magnetocaloric performances in antiferromagnetic Gd6WO12 ceramic","authors":"Xiaoli Gong , Mahdi Feizpour , Yikun Zhang , Touradj Ebadzadeh , Lingwei Li","doi":"10.1016/j.jmmm.2026.173886","DOIUrl":"10.1016/j.jmmm.2026.173886","url":null,"abstract":"<div><div>The magnetocaloric (MC) performances in many rare-earth (<em>RE</em>)-dominated ceramics have been extensively explored in the search for suitable candidates for cryogenic magnetic refrigeration (MR) applications. Herein, a single-phased Gd<sub>6</sub>WO<sub>12</sub> ceramic was synthesized via a solid-state route, and its crystal structure, elemental valence states, magnetic phase transition (MPT), and cryogenic MC properties were systematically investigated. The results showed that the Gd<sub>6</sub>WO<sub>12</sub> crystallizes in a trigonal <em>R</em>-3 structure and exhibits antiferromagnetic ordering at the Néel temperature of 2.9 K. The constituent elements are homogeneously distributed and adopt the expected valence states of Gd<sup>3+</sup>, W<sup>6+</sup>, and O<sup>2−</sup>. A considerable and reversible cryogenic MC effect in antiferromagnetic Gd<sub>6</sub>WO<sub>12</sub> was observed which is associated with its field-induced first-order MPT. The MC parameters of maximum magnetic entropy change/temperature-averaged entropy change and relative cooling power/refrigerant capacity (magnetic-field change = 0–7 T) of Gd<sub>6</sub>WO<sub>12</sub> ceramic are determined as 21.7/19.7 J·kg<sup>−1</sup>·K<sup>−1</sup> and 193.9/256.8 J·kg<sup>−1</sup>, respectively. These values are surpassing those of <em>RE</em><sub>6</sub>MoO<sub>12</sub> ceramics and comparable to some recently reported high-performance <em>RE</em>-dominated MC materials, indicating that the antiferromagnetic Gd<sub>6</sub>WO<sub>12</sub> ceramic could be a considerable candidate material for cryogenic refrigeration applications.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"642 ","pages":"Article 173886"},"PeriodicalIF":3.0,"publicationDate":"2026-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146185937","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-15Epub Date: 2026-01-29DOI: 10.1016/j.jmmm.2026.173883
Yida Lei , Kui Liu , Yang Xiao , Yanlin Ma , Jie Li , Huaiwu Zhang
The development of self-biased ferrite materials is crucial for the miniaturization of non-reciprocal devices in communication systems. However, conventional BaM ferrites typically exhibit low remanence ratio (Mr/Ms), high sintering temperature, and high losses, which severely limit their practical applications. In this work, we present a novel textured ferrite ceramic, BaFe12-x(Sn0.5Mg0.5)xO19 (x = 0.00–0.48), synthesized via a solid-state reaction combined with magnetic orientation. The results demonstrate that Sn4+ and Mg2+ ions were successfully incorporated into the ferrite lattice, leading to refined grain size and improved sample density. Notably, the composition with x = 0.24 exhibited excellent magnetic properties: Ms = 61.90 emu/g, Mr/Ms = 0.845, Hc = 1815 Oe, and ΔH = 1505 Oe (at 60 GHz). Compared with undoped BaM ferrites, this optimized material can be sintered at lower temperatures while achieving markedly higher Mr and a 43.81% reduction in FMR linewidth. By fitting the frequency-dependent ΔH values between 60 and 70 GHz, the Gilbert damping (α) is determined to be 0.0696. These improvements make the Sn-Mg co-doped, textured BaM hexaferrite a promising candidate for next-generation self-biased nonreciprocity devices.
{"title":"Sn-Mg co-doping in textured BaM ferrites: modulation of magnetic and millimeter-wave properties","authors":"Yida Lei , Kui Liu , Yang Xiao , Yanlin Ma , Jie Li , Huaiwu Zhang","doi":"10.1016/j.jmmm.2026.173883","DOIUrl":"10.1016/j.jmmm.2026.173883","url":null,"abstract":"<div><div>The development of self-biased ferrite materials is crucial for the miniaturization of non-reciprocal devices in communication systems. However, conventional BaM ferrites typically exhibit low remanence ratio (<em>M</em><sub><em>r</em></sub>/<em>M</em><sub><em>s</em></sub>), high sintering temperature, and high losses, which severely limit their practical applications. In this work, we present a novel textured ferrite ceramic, BaFe<sub>12-<em>x</em></sub>(Sn<sub>0.5</sub>Mg<sub>0.5</sub>)<sub><em>x</em></sub>O<sub>19</sub> (<em>x</em> = 0.00–0.48), synthesized via a solid-state reaction combined with magnetic orientation. The results demonstrate that Sn<sup>4+</sup> and Mg<sup>2+</sup> ions were successfully incorporated into the ferrite lattice, leading to refined grain size and improved sample density. Notably, the composition with <em>x</em> = 0.24 exhibited excellent magnetic properties: <em>M</em><sub><em>s</em></sub> = 61.90 emu/g, <em>M</em><sub><em>r</em></sub>/<em>M</em><sub><em>s</em></sub> = 0.845, <em>H</em><sub><em>c</em></sub> = 1815 Oe, and Δ<em>H</em> = 1505 Oe (at 60 GHz). Compared with undoped BaM ferrites, this optimized material can be sintered at lower temperatures while achieving markedly higher <em>M</em><sub><em>r</em></sub> and a 43.81% reduction in FMR linewidth. By fitting the frequency-dependent Δ<em>H</em> values between 60 and 70 GHz, the Gilbert damping (<em>α</em>) is determined to be 0.0696. These improvements make the Sn-Mg co-doped, textured BaM hexaferrite a promising candidate for next-generation self-biased nonreciprocity devices.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"642 ","pages":"Article 173883"},"PeriodicalIF":3.0,"publicationDate":"2026-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146076816","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-15Epub Date: 2026-02-06DOI: 10.1016/j.jmmm.2026.173909
Yuan Zhuang , Le-Zhong Li , Lin-Jie Guo , Xing Zhang , Zu-Heng Hu , Bing-jie Wang , Feng Xu , Jian Tang , Yi-Lei Li
Rare-earth perovskite ferrites are ideal candidates for multiferroics, memristors, and low-power spintronic devices due to their excellent chemical stability and highly tunable A-site structure. However, their room-temperature applications are severely limited by weak canted antiferromagnetism and low dielectric constant. In this study, Gd1-xCexFeO3 (GCFO, x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5) were synthesized via dual-valence Ce3+/Ce4+ substitution. The large differences in ionic radius and valence between Ce3+ and Ce4+ induce intense lattice distortion, significantly enhancing the Dzyaloshinskii-Moriya interaction and introducing a stronger ferromagnetic component. Simultaneously, the charge imbalance generated by Ce4+ creates abundant oxygen vacancies, enabling effective modulation of dielectric properties. Phase analysis confirms that all samples maintain the orthorhombic perovskite structure. EDS and XPS verify successful Ce incorporation, while the characteristic Ce4+ satellite peak near 916 eV in the Ce 3d spectra clearly confirms Ce3+/Ce4+ coexistence and increased oxygen vacancy concentration. Magnetic measurements reveal that Ce-substituted GCFO undergoes a transition from canted antiferromagnetism to pronounced weak ferromagnetism, with saturation magnetization increasing from 1.05 emu/g (x = 0) to 1.94 emu/g (x = 0.4). Dielectric measurements reveal that the x = 0.2 sample exhibits a dielectric constant as high as 1.55 × 104 at 102 Hz while maintaining relatively low dielectric loss. Furthermore, this composition demonstrates the lowest activation energy (0.077 eV) and DC resistivity (8.34 × 108 Ω·m at 300 K) among all substitution levels. This universal dual-valence substitution strategy concurrently achieves room-temperature weak ferromagnetism and an enhanced dielectric response, offering a promising material platform for advanced high-performance electronic devices.
{"title":"Dual-valence Ce substitution induces weak ferromagnetism and colossal dielectric response in GdFeO3","authors":"Yuan Zhuang , Le-Zhong Li , Lin-Jie Guo , Xing Zhang , Zu-Heng Hu , Bing-jie Wang , Feng Xu , Jian Tang , Yi-Lei Li","doi":"10.1016/j.jmmm.2026.173909","DOIUrl":"10.1016/j.jmmm.2026.173909","url":null,"abstract":"<div><div>Rare-earth perovskite ferrites are ideal candidates for multiferroics, memristors, and low-power spintronic devices due to their excellent chemical stability and highly tunable A-site structure. However, their room-temperature applications are severely limited by weak canted antiferromagnetism and low dielectric constant. In this study, Gd<sub>1-<em>x</em></sub>Ce<sub><em>x</em></sub>FeO<sub>3</sub> (GCFO, <em>x</em> = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5) were synthesized via dual-valence Ce<sup>3+</sup>/Ce<sup>4+</sup> substitution. The large differences in ionic radius and valence between Ce<sup>3+</sup> and Ce<sup>4+</sup> induce intense lattice distortion, significantly enhancing the Dzyaloshinskii-Moriya interaction and introducing a stronger ferromagnetic component. Simultaneously, the charge imbalance generated by Ce<sup>4+</sup> creates abundant oxygen vacancies, enabling effective modulation of dielectric properties. Phase analysis confirms that all samples maintain the orthorhombic perovskite structure. EDS and XPS verify successful Ce incorporation, while the characteristic Ce<sup>4+</sup> satellite peak near 916 eV in the Ce 3d spectra clearly confirms Ce<sup>3+</sup>/Ce<sup>4+</sup> coexistence and increased oxygen vacancy concentration. Magnetic measurements reveal that Ce-substituted GCFO undergoes a transition from canted antiferromagnetism to pronounced weak ferromagnetism, with saturation magnetization increasing from 1.05 emu/g (<em>x</em> = 0) to 1.94 emu/g (<em>x</em> = 0.4). Dielectric measurements reveal that the <em>x</em> = 0.2 sample exhibits a dielectric constant as high as 1.55 × 10<sup>4</sup> at 10<sup>2</sup> Hz while maintaining relatively low dielectric loss. Furthermore, this composition demonstrates the lowest activation energy (0.077 eV) and DC resistivity (8.34 × 10<sup>8</sup> Ω·m at 300 K) among all substitution levels. This universal dual-valence substitution strategy concurrently achieves room-temperature weak ferromagnetism and an enhanced dielectric response, offering a promising material platform for advanced high-performance electronic devices.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"642 ","pages":"Article 173909"},"PeriodicalIF":3.0,"publicationDate":"2026-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146185899","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-15Epub Date: 2026-01-31DOI: 10.1016/j.jmmm.2026.173897
Michal Ulvr , Franziska Weickert , Korbinian Pfnuer , Joachim Lüdke , Katja Hoffmann , Stuart Harmon , Daniel Brunt , Adam Wilson , Massimo Pasquale , Carlo Appino , Chris Gerada , Ram Ramanathan Mathavan jeyabalan , Gaurang Vakil
Epstein frame and single sheet tester are two methods used for measurement of power losses of the electrical steel sheets or strips. Both methods and the setups are described in the IEC standards. Each national metrology institute or other metrological laboratory has different setups for power losses measurement and the validation of its accuracy and parameters can only be done by comparisons. So far, every performed comparison was carried out only at 50 Hz or 60 Hz. Within the EMPIR project “HEFMAG”, improved metrological infrastructure for the determination of power losses using Epstein frame at induction values close to saturation and at frequency ranges between 2 kHz and to 10 kHz was built. To validate the improved setups, a round robin comparison of power loss measurements was conducted by five laboratories. The results of the round robin comparison are discussed including measurement uncertainties.
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We present a perspective on recent progress in machine-learning (ML) force-field approaches for large-scale Landau–Lifshitz–Gilbert (LLG) simulations of metallic spin systems. Building on a generalization of the Behler–Parrinello (BP) architecture originally developed for quantum molecular dynamics, we develop scalable and transferable ML models that faithfully capture the complex, environment-dependent electron-mediated exchange fields characteristic of itinerant magnets. A central ingredient of this framework is the implementation of symmetry-aware magnetic descriptors based on group-theoretical bispectrum formalisms. Leveraging these ML force fields, LLG simulations faithfully reproduce hallmark non-collinear magnetic orders—such as the 120° and tetrahedral states—on the triangular lattice, and successfully capture the complex spin textures emerging in the mixed-phase states of a square-lattice double-exchange model under thermal quench. We further discuss a generalized potential theory that extends the BP formalism to incorporate both conservative and nonconservative electronic torques, thereby enabling ML models to learn nonequilibrium exchange fields from computationally demanding microscopic approaches such as nonequilibrium Green’s-function techniques. This extension yields quantitatively accurate predictions of voltage-driven domain-wall motion and establishes a foundation for quantum-accurate, multiscale modeling of nonequilibrium spin dynamics and spintronic functionalities.
{"title":"Machine-learning modeling of magnetization dynamics in quasi-equilibrium and driven metallic spin systems","authors":"Gia-Wei Chern, Yunhao Fan, Sheng Zhang, Puhan Zhang","doi":"10.1016/j.jmmm.2026.173898","DOIUrl":"10.1016/j.jmmm.2026.173898","url":null,"abstract":"<div><div>We present a perspective on recent progress in machine-learning (ML) force-field approaches for large-scale Landau–Lifshitz–Gilbert (LLG) simulations of metallic spin systems. Building on a generalization of the Behler–Parrinello (BP) architecture originally developed for quantum molecular dynamics, we develop scalable and transferable ML models that faithfully capture the complex, environment-dependent electron-mediated exchange fields characteristic of itinerant magnets. A central ingredient of this framework is the implementation of symmetry-aware magnetic descriptors based on group-theoretical bispectrum formalisms. Leveraging these ML force fields, LLG simulations faithfully reproduce hallmark non-collinear magnetic orders—such as the 120° and tetrahedral states—on the triangular lattice, and successfully capture the complex spin textures emerging in the mixed-phase states of a square-lattice double-exchange model under thermal quench. We further discuss a generalized potential theory that extends the BP formalism to incorporate both conservative and nonconservative electronic torques, thereby enabling ML models to learn nonequilibrium exchange fields from computationally demanding microscopic approaches such as nonequilibrium Green’s-function techniques. This extension yields quantitatively accurate predictions of voltage-driven domain-wall motion and establishes a foundation for quantum-accurate, multiscale modeling of nonequilibrium spin dynamics and spintronic functionalities.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"642 ","pages":"Article 173898"},"PeriodicalIF":3.0,"publicationDate":"2026-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146185909","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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