Pub Date : 2025-11-17DOI: 10.1016/j.jmmm.2025.173687
L.M. Ramos , M. Schmidt , F.M. Zimmer
We investigated the isotropic spin- Heisenberg model on an anisotropic square lattice with competing exchange interactions, motivated by the unconventional magnetic behavior observed in the verdazyl-based compound (-MePy-V)PF. Using a cluster mean-field approach, we explore a field-induced phase stabilized by the interplay between frustration and quantum fluctuations, focusing on the role of exchange interactions. We identify: (i) the formation of spin singlet pairs, signaled by enhanced spin–spin correlations in specific field regimes; and (ii) a one-half magnetization plateau, emerging from a subtle balance between competing exchange couplings and field-enhanced quantum fluctuations. Our results reveal that an enhancement of frustration, achieved by tuning small variations in the spatially anisotropic exchange interactions of the compound (-MePy-V)PF, can stabilize a field-induced quantum phase where ferromagnetism coexists with antiferromagnetic dimers. Our results provide microscopic insight into the mechanisms driving these nontrivial phases and offer theoretical support for interpreting experimental observations in this class of low-dimensional quantum magnets.
{"title":"Spin–singlet dimer phase in a frustrated square lattice under a magnetic field","authors":"L.M. Ramos , M. Schmidt , F.M. Zimmer","doi":"10.1016/j.jmmm.2025.173687","DOIUrl":"10.1016/j.jmmm.2025.173687","url":null,"abstract":"<div><div>We investigated the isotropic spin-<span><math><mfrac><mrow><mn>1</mn></mrow><mrow><mn>2</mn></mrow></mfrac></math></span> Heisenberg model on an anisotropic square lattice with competing exchange interactions, motivated by the unconventional magnetic behavior observed in the verdazyl-based compound (<span><math><mi>o</mi></math></span>-MePy-V)PF<span><math><msub><mrow></mrow><mrow><mn>6</mn></mrow></msub></math></span>. Using a cluster mean-field approach, we explore a field-induced phase stabilized by the interplay between frustration and quantum fluctuations, focusing on the role of exchange interactions. We identify: (i) the formation of spin singlet pairs, signaled by enhanced spin–spin correlations in specific field regimes; and (ii) a one-half magnetization plateau, emerging from a subtle balance between competing exchange couplings and field-enhanced quantum fluctuations. Our results reveal that an enhancement of frustration, achieved by tuning small variations in the spatially anisotropic exchange interactions of the compound (<span><math><mi>o</mi></math></span>-MePy-V)PF<span><math><msub><mrow></mrow><mrow><mn>6</mn></mrow></msub></math></span>, can stabilize a field-induced quantum phase where ferromagnetism coexists with antiferromagnetic dimers. Our results provide microscopic insight into the mechanisms driving these nontrivial phases and offer theoretical support for interpreting experimental observations in this class of low-dimensional quantum magnets.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"637 ","pages":"Article 173687"},"PeriodicalIF":3.0,"publicationDate":"2025-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145578499","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 : 2025-11-15DOI: 10.1016/j.jmmm.2025.173683
Xianfei Yin , Fei Chen , Mingzhuang Wu , Aimin Li , Haopeng Li , Shuyou Wang
Aiming at the problem that the existing magnetorheological (MR) fluid shear stress measurement system lacks effective heat dissipation, this paper proposes a new liquid-cooled measurement system. The structure of the measurement system is designed, and the expression of the MR fluid shear yield stress of the measurement system is derived. Theoretical analysis and finite element simulation analysis are carried out on the magnetic field and temperature field of the measurement system, which verify the rationality of the magnetic circuit design and the effectiveness of heat dissipation. The measurement system is built and its performance is verified. The results show that the measurement system can provide a magnetic field strength of 650 mT, a temperature rise of less than 5 °C, and a measurement accuracy of more than 98 %.
{"title":"Liquid-cooled yield stress measurement system for magnetorheological fluids","authors":"Xianfei Yin , Fei Chen , Mingzhuang Wu , Aimin Li , Haopeng Li , Shuyou Wang","doi":"10.1016/j.jmmm.2025.173683","DOIUrl":"10.1016/j.jmmm.2025.173683","url":null,"abstract":"<div><div>Aiming at the problem that the existing magnetorheological (MR) fluid shear stress measurement system lacks effective heat dissipation, this paper proposes a new liquid-cooled measurement system. The structure of the measurement system is designed, and the expression of the MR fluid shear yield stress of the measurement system is derived. Theoretical analysis and finite element simulation analysis are carried out on the magnetic field and temperature field of the measurement system, which verify the rationality of the magnetic circuit design and the effectiveness of heat dissipation. The measurement system is built and its performance is verified. The results show that the measurement system can provide a magnetic field strength of 650 mT, a temperature rise of less than 5 °C, and a measurement accuracy of more than 98 %.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"637 ","pages":"Article 173683"},"PeriodicalIF":3.0,"publicationDate":"2025-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145532758","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 : 2025-11-15DOI: 10.1016/j.jmmm.2025.173674
Yuan Zhuang , Yi-Lei Li , Lin-Jie Guo , Xing Zhang , Zu-Heng Hu , Le-Zhong Li , Jian Tang
This study synthesized Ni0.5Zn0.35Co0.15ErxFe2-xO4 (NZCEF, 0 ≤ x ≤ 0.100) ferrite ceramics and systematically investigated the influence of Er3+ substitution, along with the synergistically formed secondary phase, on the microstructure, dielectric-resistivity properties, and magnetic performance. The results demonstrate the material's promising potential for next-generation wireless communication and high-frequency power inductors. XRD analysis confirmed that all substituted ferrites maintained the spinel structure, with theoretical density increasing and porosity decreasing as the substitution level rose. A secondary ErFeO3 phase emerged at x = 0.025, reaching a phase fraction of 11.06 % at x = 0.1. Scanning electron microscopy revealed that the average grain size decreased from 1.78 μm to 1.26 μm, consistent with the trend of calculated crystallite size (D). Regarding magnetic properties, both the calculated anisotropy field (Ha) and effective anisotropy constant (Kₑff) increased gradually with substitution level. The measured saturation magnetization decreased from 53.65 emu/g to 40.26 emu/g, while coercivity increased from 37.56 Oe to 45.46 Oe, validating the computational reliability. Notably, the resonance frequency significantly improved to 407.9 MHz, surpassing the benchmark of mainstream IEEE 802.15.4 Sub-GHz high-frequency devices. For the dielectric-resistivity properties, Er3+ substitution and the formation of the secondary phase altered the electron hopping mechanism between Fe3+ and Fe2+ ions, significantly reducing dielectric loss. At x = 0.05, the activation energy (Eₐ) markedly increases to 0.508 eV, and the resistivity reaches a peak value of 6.50 × 106 Ω·m at 321 K. This work demonstrates the synergistic effects of Er3+ substitution and secondary phase formation in enhancing dielectric properties, reducing losses, and increasing resonance frequency, thereby positioning the material as an ideal candidate for wireless communication systems, RF power amplifier modules, and high-speed IoT applications.
{"title":"Effect of Er substitution on structural, magnetic, and dielectric-resistivity properties of NiZnCo ferrite","authors":"Yuan Zhuang , Yi-Lei Li , Lin-Jie Guo , Xing Zhang , Zu-Heng Hu , Le-Zhong Li , Jian Tang","doi":"10.1016/j.jmmm.2025.173674","DOIUrl":"10.1016/j.jmmm.2025.173674","url":null,"abstract":"<div><div>This study synthesized Ni<sub>0.5</sub>Zn<sub>0.35</sub>Co<sub>0.15</sub>Er<sub><em>x</em></sub>Fe<sub>2-<em>x</em></sub>O<sub>4</sub> (NZCEF, 0 ≤ <em>x</em> ≤ 0.100) ferrite ceramics and systematically investigated the influence of Er<sup>3+</sup> substitution, along with the synergistically formed secondary phase, on the microstructure, dielectric-resistivity properties, and magnetic performance. The results demonstrate the material's promising potential for next-generation wireless communication and high-frequency power inductors. XRD analysis confirmed that all substituted ferrites maintained the spinel structure, with theoretical density increasing and porosity decreasing as the substitution level rose. A secondary ErFeO<sub>3</sub> phase emerged at <em>x</em> = 0.025, reaching a phase fraction of 11.06 % at <em>x</em> = 0.1. Scanning electron microscopy revealed that the average grain size decreased from 1.78 μm to 1.26 μm, consistent with the trend of calculated crystallite size (<em>D</em>). Regarding magnetic properties, both the calculated anisotropy field (<em>H</em>a) and effective anisotropy constant (K<sub><em>ₑff</em></sub>) increased gradually with substitution level. The measured saturation magnetization decreased from 53.65 emu/g to 40.26 emu/g, while coercivity increased from 37.56 Oe to 45.46 Oe, validating the computational reliability. Notably, the resonance frequency significantly improved to 407.9 MHz, surpassing the benchmark of mainstream IEEE 802.15.4 Sub-GHz high-frequency devices. For the dielectric-resistivity properties, Er<sup>3+</sup> substitution and the formation of the secondary phase altered the electron hopping mechanism between Fe<sup>3+</sup> and Fe<sup>2+</sup> ions, significantly reducing dielectric loss. At <em>x</em> = 0.05, the activation energy (<em>E</em>ₐ) markedly increases to 0.508 eV, and the resistivity reaches a peak value of 6.50 × 10<sup>6</sup> Ω·m at 321 K. This work demonstrates the synergistic effects of Er<sup>3+</sup> substitution and secondary phase formation in enhancing dielectric properties, reducing losses, and increasing resonance frequency, thereby positioning the material as an ideal candidate for wireless communication systems, RF power amplifier modules, and high-speed IoT applications.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"637 ","pages":"Article 173674"},"PeriodicalIF":3.0,"publicationDate":"2025-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145621890","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}
This study presents the hydrothermal synthesis of samarium (Sm) doped ZnO nanocrystals, coupled with a comprehensive experimental and first-principles computational investigation to elucidate their structural, electronic, and magneto-optical properties. X-ray diffraction and energy-dispersive X-ray spectroscopy confirm high crystallinity and purity of the doped nanocrystals, with no detectable secondary phases. X-ray photoelectron spectroscopy verifies successful incorporation of Sm3+ ions and the presence of oxygen vacancies (VO). Doping induces two critical effects: a reduction in the optical bandgap and the emergence of room-temperature paramagnetism in ZnO. First-principles calculations further reveal that Sm doping enhances magneto-optical properties through two key mechanisms: high-spin polarization of Sm-4f energy levels and modulation of the host band structure. Notably, while oxygen vacancies contribute minimally to individual magnetic moments, they act as critical mediators of magnetic coupling between Sm3+ ions via bound magnetic polarons. Specifically, both Sm-O-Sm atomic configurations and Sm-VO-Sm defect complexes facilitate robust ferromagnetic coupling, enabling room temperature ferromagnetism in the doped nanocrystals. These findings highlight the potential of Sm doped ZnO for advanced spintronic applications, where tunable magnetic and magneto-optical properties are essential.
{"title":"Magnetic coupling mediated by oxygen vacancies in Sm doped ZnO nanocrystals: Hydrothermal synthesis and first-principles investigation","authors":"Hao Yuan , Yanfang Zhao , Dongbo Li , Jian Lv , Ping Zhou , Xinyao Li , Yuanbin Xiao , Wei Ding","doi":"10.1016/j.jmmm.2025.173684","DOIUrl":"10.1016/j.jmmm.2025.173684","url":null,"abstract":"<div><div>This study presents the hydrothermal synthesis of samarium (Sm) doped ZnO nanocrystals, coupled with a comprehensive experimental and first-principles computational investigation to elucidate their structural, electronic, and magneto-optical properties. X-ray diffraction and energy-dispersive X-ray spectroscopy confirm high crystallinity and purity of the doped nanocrystals, with no detectable secondary phases. X-ray photoelectron spectroscopy verifies successful incorporation of Sm<sup>3+</sup> ions and the presence of oxygen vacancies (V<sub>O</sub>). Doping induces two critical effects: a reduction in the optical bandgap and the emergence of room-temperature paramagnetism in ZnO. First-principles calculations further reveal that Sm doping enhances magneto-optical properties through two key mechanisms: high-spin polarization of Sm-4f energy levels and modulation of the host band structure. Notably, while oxygen vacancies contribute minimally to individual magnetic moments, they act as critical mediators of magnetic coupling between Sm<sup>3+</sup> ions via bound magnetic polarons. Specifically, both Sm-O-Sm atomic configurations and Sm-V<sub>O</sub>-Sm defect complexes facilitate robust ferromagnetic coupling, enabling room temperature ferromagnetism in the doped nanocrystals. These findings highlight the potential of Sm doped ZnO for advanced spintronic applications, where tunable magnetic and magneto-optical properties are essential.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"637 ","pages":"Article 173684"},"PeriodicalIF":3.0,"publicationDate":"2025-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145578498","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 : 2025-11-15DOI: 10.1016/j.jmmm.2025.173680
S.P. Xhakaza, A.M. Strydom
We have investigated the behaviour of site-selective substitution in the intermetallic compound CeRhGa which has coinciding crystal structure and valence transitions at K, by means of magnetic susceptibility and specific heat. Substitutions were performed on each of the Ce, Rh, and Ga sites to a level of . All the substituted samples proved to crystallize at room temperature in the expected orthorhombic LaNi-type (, nr. 64), demonstrating the structural robustness of the host lattice upon doping. In only two of the compounds, namely Ce1.8La0.2RhGa and CeRhGa0.9Al0.1 was the transition at found to disappear.
本文利用磁化率和比热研究了具有相同晶体结构和价态跃迁的金属间化合物Ce2Rh2Ga在Tt=128.5 K时的选择性取代行为。将Ce、Rh和Ga位点置换至10at.%的水平。所有取代的样品在室温下都以预期的正交la2ni3型（Cmce, nr. 64）结晶，证明了掺杂后主体晶格的结构稳健性。其中只有Ce1.8La0.2Rh2Ga和Ce2Rh2Ga0.9Al0.1的Tt跃迁消失。
{"title":"Probing the valence transition in Ce2Rh2Ga by chemical pressure","authors":"S.P. Xhakaza, A.M. Strydom","doi":"10.1016/j.jmmm.2025.173680","DOIUrl":"10.1016/j.jmmm.2025.173680","url":null,"abstract":"<div><div>We have investigated the behaviour of site-selective substitution in the intermetallic compound Ce<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>Rh<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>Ga which has coinciding crystal structure and valence transitions at <span><math><mrow><msub><mrow><mi>T</mi></mrow><mrow><mi>t</mi></mrow></msub><mo>=</mo><mn>128</mn><mo>.</mo><mn>5</mn></mrow></math></span> K, by means of magnetic susceptibility and specific heat. Substitutions were performed on each of the Ce, Rh, and Ga sites to a level of <span><math><mrow><mn>10</mn><mspace></mspace><mi>at</mi><mo>.</mo><mspace></mspace><mtext>%</mtext></mrow></math></span>. All the substituted samples proved to crystallize at room temperature in the expected orthorhombic La<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>Ni<span><math><msub><mrow></mrow><mrow><mn>3</mn></mrow></msub></math></span>-type (<span><math><mrow><mi>C</mi><mi>m</mi><mi>c</mi><mi>e</mi></mrow></math></span>, nr. 64), demonstrating the structural robustness of the host lattice upon doping. In only two of the compounds, namely Ce<sub>1.8</sub>La<sub>0.2</sub>Rh<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>Ga and Ce<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>Rh<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>Ga<sub>0.9</sub>Al<sub>0.1</sub> was the transition at <span><math><msub><mrow><mi>T</mi></mrow><mrow><mi>t</mi></mrow></msub></math></span> found to disappear.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"637 ","pages":"Article 173680"},"PeriodicalIF":3.0,"publicationDate":"2025-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145578500","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 : 2025-11-15DOI: 10.1016/j.jmmm.2025.173685
Papiya Saha , R. Nithya , K. Sethupathi , P.K. Sreejith , Rabindra Nath Juine , Sujoy Sen
Mn-based double perovskite oxides are gaining huge interest due to their multivalent oxidation state resulting in unique magnetic and optical properties. Double perovskite oxide Y2ZnMnO6 is synthesized for the first time using solid state reaction route. The correlation between the structural, magnetic and optical properties are reported here. It crystallizes in monoclinic structure with the space group, P21/n and the lattice parameters are a = 5.257 (5) Å, b = 5.614 (3) Å, c = 7.512 (3) Å, β = 90.03 (2)°. Significant octahedral tilting is observed. The obtained values of bond valence sum confirm the stoichiometry. Temperature dependent DC magnetization measurements under ZFC, FCC and FCW protocols showed an antiferromagnetic transition (TN) at 14.8 K. The super-exchange interaction between Mn4+, orbitals via Mn-O2-O3-Mn and Mn-O1-Zn-O1-Mn are responsible for the antiferromagnetic transition. The obtained values of Curie Weiss temperature and effective magnetic moment are 7.62 K and 4.41 μB respectively. The absence of spin glass state is confirmed from AC susceptibility results. The bifurcation between magnetic susceptibility under ZFC, FC modes below the Neel temperature (TN) could be due to the presence of weak ferromagnetism. Conduction mechanism switching at temperatures around 190 K from small polaron hopping to Arrhenius type has also been verified. Y2ZnMnO6 absorbs light from 250 nm to 500 nm due to the charge transfer band Mn4+-O2− transition. The direct bandgap value of 2.5 eV is obtained from the Tauc's plot. All these properties make Y2ZnMnO6 an interesting and potential candidate for opto-electronic device applications.
{"title":"Correlation between structural-magnetic-optical properties of new double perovskite oxide Y2ZnMnO6","authors":"Papiya Saha , R. Nithya , K. Sethupathi , P.K. Sreejith , Rabindra Nath Juine , Sujoy Sen","doi":"10.1016/j.jmmm.2025.173685","DOIUrl":"10.1016/j.jmmm.2025.173685","url":null,"abstract":"<div><div>Mn-based double perovskite oxides are gaining huge interest due to their multivalent oxidation state resulting in unique magnetic and optical properties. Double perovskite oxide Y<sub>2</sub>ZnMnO<sub>6</sub> is synthesized for the first time using solid state reaction route. The correlation between the structural, magnetic and optical properties are reported here. It crystallizes in monoclinic structure with the space group, <em>P2</em><sub><em>1</em></sub><em>/n</em> and the lattice parameters are <em>a</em> = 5.257 (5) Å, <em>b</em> = 5.614 (3) Å, <em>c</em> = 7.512 (3) Å, β = 90.03 (2)°. Significant octahedral tilting is observed. The obtained values of bond valence sum confirm the stoichiometry. Temperature dependent DC magnetization measurements under ZFC, FCC and FCW protocols showed an antiferromagnetic transition (T<sub>N</sub>) at 14.8 K. The super-exchange interaction between Mn<sup>4+</sup>, <span><math><msubsup><mi>t</mi><mrow><mn>2</mn><mi>g</mi></mrow><mn>3</mn></msubsup></math></span> orbitals via Mn-O2-O3-Mn and Mn-O1-Zn-O1-Mn are responsible for the antiferromagnetic transition. The obtained values of Curie Weiss temperature and effective magnetic moment are 7.62 K and 4.41 μ<sub>B</sub> respectively. The absence of spin glass state is confirmed from AC susceptibility results. The bifurcation between magnetic susceptibility under ZFC, FC modes below the Neel temperature (T<sub>N</sub>) could be due to the presence of weak ferromagnetism. Conduction mechanism switching at temperatures around 190 K from small polaron hopping to Arrhenius type has also been verified. Y<sub>2</sub>ZnMnO<sub>6</sub> absorbs light from 250 nm to 500 nm due to the charge transfer band Mn<sup>4+</sup>-O<sup>2−</sup> transition. The direct bandgap value of 2.5 eV is obtained from the Tauc's plot. All these properties make Y<sub>2</sub>ZnMnO<sub>6</sub> an interesting and potential candidate for opto-electronic device applications.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"637 ","pages":"Article 173685"},"PeriodicalIF":3.0,"publicationDate":"2025-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145532756","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 : 2025-11-15DOI: 10.1016/j.jmmm.2025.173676
Abdelhak Chebli , Joan Josep Suñol , Daniel Nižňanský , Baris Avar
In this study, nanocrystalline Fe25Se75 powders were synthesized by high-energy mechanical alloying (MA) for milling times up to 52 h. The evolution of the crystalline structure, hyperfine parameters, and magnetic behavior was investigated using Mössbauer spectroscopy (MS), vibrating sample magnetometry (VSM), and X-ray diffraction (XRD). The Mössbauer spectra of samples milled up to 33 h showed a dominant paramagnetic doublet, corresponding to the formation of the FeSe2 phase, alongside a sextet from residual α-Fe. However, after 52 h of milling, the spectra showed the emergence of a broad ferromagnetic sextet, indicating a phase transformation from paramagnetic FeSe2 to ferromagnetic Fe7Se8. This magnetic transition is supported by VSM measurements performed at room temperature for samples milled for 1, 6, 10, 33, and 52 h. The VSM data confirmed the presence of a ferromagnetic phase at extended milling times, characterized by a progressive increase in coercivity (Hc) and a sharp decrease in saturation magnetization (Ms). X-ray diffraction (XRD) patterns corroborated the phase identification and structural information revealed by Mössbauer spectroscopy.
These findings highlight the capability of MA to induce phase transformations and demonstrate that the combination of MS and VSM is highly effective for tracking the magnetic transition from paramagnetic FeSe2 to ferromagnetic Fe7Se8.
{"title":"Detection of FeSe2 paramagnetic to Fe7Se8 ferromagnetic transition in FeSe by Mössbauer spectroscopy","authors":"Abdelhak Chebli , Joan Josep Suñol , Daniel Nižňanský , Baris Avar","doi":"10.1016/j.jmmm.2025.173676","DOIUrl":"10.1016/j.jmmm.2025.173676","url":null,"abstract":"<div><div>In this study, nanocrystalline Fe<sub>25</sub>Se<sub>75</sub> powders were synthesized by high-energy mechanical alloying (MA) for milling times up to 52 h. The evolution of the crystalline structure, hyperfine parameters, and magnetic behavior was investigated using Mössbauer spectroscopy (MS), vibrating sample magnetometry (VSM), and X-ray diffraction (XRD). The Mössbauer spectra of samples milled up to 33 h showed a dominant paramagnetic doublet, corresponding to the formation of the FeSe2 phase, alongside a sextet from residual α-Fe. However, after 52 h of milling, the spectra showed the emergence of a broad ferromagnetic sextet, indicating a phase transformation from paramagnetic FeSe<sub>2</sub> to ferromagnetic Fe<sub>7</sub>Se<sub>8</sub>. This magnetic transition is supported by VSM measurements performed at room temperature for samples milled for 1, 6, 10, 33, and 52 h. The VSM data confirmed the presence of a ferromagnetic phase at extended milling times, characterized by a progressive increase in coercivity (Hc) and a sharp decrease in saturation magnetization (Ms). X-ray diffraction (XRD) patterns corroborated the phase identification and structural information revealed by Mössbauer spectroscopy.</div><div>These findings highlight the capability of MA to induce phase transformations and demonstrate that the combination of MS and VSM is highly effective for tracking the magnetic transition from paramagnetic FeSe<sub>2</sub> to ferromagnetic Fe<sub>7</sub>Se<sub>8</sub>.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"637 ","pages":"Article 173676"},"PeriodicalIF":3.0,"publicationDate":"2025-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145621889","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 : 2025-11-14DOI: 10.1016/j.jmmm.2025.173675
Jue Wang , Youning Kang , Chen Zhang , Dongtao Zhang , Jianjun Yang , Yuqing Li , Weiqiang Liu , Ming Yue
Increasing the Fe content constitutes a strategy for enhancing the remanence and maximum energy product of 2:17-type SmCo alloys. However, it typically compromises coercivity and squareness ratio. In this study, a dual-alloy approach was employed, where in a high-Fe and low-Cu alloy A with a low-Fe and high-Cu alloy B, followed by sintering to fabricate a composite magnet C. Compared with the single-alloy A magnet, the dual-alloy magnet C achieves a significant increase in coercivity to 33.1 kOe and squareness ratio from 40.7 % to 42.6 %, while maintaining comparable remanence. The analysis revealed that the dual-alloy process optimized the volume fraction of the 1:3R platelet phase and the distribution of the 1:5H cell-boundary phase, resulting in a more uniform cellular structure, reducing the density of the 2:17R’ phase, and altering the domain-wall pinning mechanism. This methodology overcomes the limitations inherent in conventional composition design, offering a viable strategy for developing high-performance, high-Fe 2:17-type SmCo alloys with significant application potential.
{"title":"Investigation of coercivity and squareness in high-Fe 2:17-type SmCo alloys fabricated via dual-alloy process","authors":"Jue Wang , Youning Kang , Chen Zhang , Dongtao Zhang , Jianjun Yang , Yuqing Li , Weiqiang Liu , Ming Yue","doi":"10.1016/j.jmmm.2025.173675","DOIUrl":"10.1016/j.jmmm.2025.173675","url":null,"abstract":"<div><div>Increasing the Fe content constitutes a strategy for enhancing the remanence and maximum energy product of 2:17-type SmCo alloys. However, it typically compromises coercivity and squareness ratio. In this study, a dual-alloy approach was employed, where in a high-Fe and low-Cu alloy A with a low-Fe and high-Cu alloy B, followed by sintering to fabricate a composite magnet C. Compared with the single-alloy A magnet, the dual-alloy magnet C achieves a significant increase in coercivity to 33.1 kOe and squareness ratio from 40.7 % to 42.6 %, while maintaining comparable remanence. The analysis revealed that the dual-alloy process optimized the volume fraction of the 1:3R platelet phase and the distribution of the 1:5H cell-boundary phase, resulting in a more uniform cellular structure, reducing the density of the 2:17R’ phase, and altering the domain-wall pinning mechanism. This methodology overcomes the limitations inherent in conventional composition design, offering a viable strategy for developing high-performance, high-Fe 2:17-type SmCo alloys with significant application potential.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"637 ","pages":"Article 173675"},"PeriodicalIF":3.0,"publicationDate":"2025-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145532755","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 : 2025-11-13DOI: 10.1016/j.jmmm.2025.173677
K.S. Al-Rashdi , H.M. Widatallah , F. Al Ma'Mari , M.E. Elzain , A.M. Gismelseed , A.D. Al-Rawas , H.H. Kyaw , O. Cespedes , E.A. Moore , E.M. Crabb
We systematically investigated the core structure, surface composition, and magnetic properties of Mn2+-doped magnetite nanocrystalline particles (∼ 8–23 nm) of the nominal composition MnxFe3-yO4 (x = 0.0–0.5; ) where the Fe3+, not Fe2+, ions are deliberately substituted with Mn2+ to create a unique defect structure formed of both substitutional and interstitial Mn2+ impurities. XRD and Raman data indicate that Mn2+ doping weakens the magnetite-to-maghemite transformation, halting it entirely for the MnxFe3-yO4 sample with x = 0.5. Rietveld analysis of XRD data favors a cationic distribution wherein Mn2+ ions exclusively substitute the tetrahedral Fe3+ ions in the spinel-related structure, removing of them to interstitial tetrahedral sites at low x values and to both interstitial tetrahedral and octahedral sites at higher x values. XPS data support the finding that the magnetite-to-maghemite transformation is increasingly inhibited at higher x values. The nanoparticles exhibit complex magnetic behavior, which is a manifestation of the unique defect structure wherein the saturation magnetization initially decreases and then increases as x increases. The Verwey transition observed at very low temperatures (∼10 K) in MnxFe3-yO4 nanoparticles is attributed to particle size effects rather than Mn2+ doping. The changes in the magnetic properties are clearly related to the unique defect structure developed.
{"title":"Structure, surface composition, and magnetic properties of Mn2+-doped magnetite nanoparticles of the composition MnxFe3-yO4","authors":"K.S. Al-Rashdi , H.M. Widatallah , F. Al Ma'Mari , M.E. Elzain , A.M. Gismelseed , A.D. Al-Rawas , H.H. Kyaw , O. Cespedes , E.A. Moore , E.M. Crabb","doi":"10.1016/j.jmmm.2025.173677","DOIUrl":"10.1016/j.jmmm.2025.173677","url":null,"abstract":"<div><div>We systematically investigated the core structure, surface composition, and magnetic properties of Mn<sup>2+</sup>-doped magnetite nanocrystalline particles (∼ 8–23 nm) of the nominal composition Mn<sub><em>x</em></sub>Fe<sub>3-<em>y</em></sub>O<sub>4</sub> (<em>x</em> = 0.0–0.5; <span><math><mi>y</mi><mo>=</mo><mfrac><mn>2</mn><mn>3</mn></mfrac><mi>x</mi></math></span>) where the Fe<sup>3+</sup>, not Fe<sup>2+</sup>, ions are deliberately substituted with Mn<sup>2+</sup> to create a unique defect structure formed of both substitutional and interstitial Mn<sup>2+</sup> impurities. XRD and Raman data indicate that Mn<sup>2+</sup> doping weakens the magnetite-to-maghemite transformation, halting it entirely for the Mn<sub><em>x</em></sub>Fe<sub>3-<em>y</em></sub>O<sub>4</sub> sample with <em>x</em> = 0.5. Rietveld analysis of XRD data favors a cationic distribution wherein Mn<sup>2+</sup> ions exclusively substitute the tetrahedral Fe<sup>3+</sup> ions in the spinel-related structure, removing <span><math><mn>⅓</mn><mspace></mspace><mi>x</mi></math></span> of them to interstitial tetrahedral sites at low <em>x</em> values and to both interstitial tetrahedral and octahedral sites at higher <em>x</em> values. XPS data support the finding that the magnetite-to-maghemite transformation is increasingly inhibited at higher <em>x</em> values. The nanoparticles exhibit complex magnetic behavior, which is a manifestation of the unique defect structure wherein the saturation magnetization initially decreases and then increases as <em>x</em> increases. The Verwey transition observed at very low temperatures (∼10 K) in Mn<sub><em>x</em></sub>Fe<sub>3-<em>y</em></sub>O<sub>4</sub> nanoparticles is attributed to particle size effects rather than Mn<sup>2+</sup> doping. The changes in the magnetic properties are clearly related to the unique defect structure developed.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"637 ","pages":"Article 173677"},"PeriodicalIF":3.0,"publicationDate":"2025-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145578502","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 : 2025-11-13DOI: 10.1016/j.jmmm.2025.173682
Junbo Li , Yihao Wang , Zhihao Li , Liang Cao , Yimin Xiong
The tunability of electronic band topology and properties by magnetic fields is of great interest for both the exploration of novel states of matter and potential applications. In the topological semimetal CeSbTe, various topological bands and magnetic structures are predicted when a magnetic field is applied along distinct crystallographic directions, particularly within the -plane. Here, we establish the in-plane (H -plane) magnetic phase diagram of CeSbTe using direct current (DC) and alternating current (AC) susceptibility measurements, and electronic transport measurements. An angle-dependent intermediate metamagnetic (IMM) phase is observed at applied fields between 2 and 3 T, suggesting the presence of competing magnetic interactions within its tetragonal Ce lattice. The observation of a topological Hall effect in the IMM phase below the Néel temperature, manifesting as a hump-like anomaly in the Hall resistivity, provides evidence for the emergence of nontrivial spin configurations. We propose that a canted antiferromagnetic state forms in this IMM phase, arising from the nontrivial spin texture during the field-induced spin-flop transition. Our study provides critical insights into competing exchange interactions in tetragonal Ce-based systems, while the tunable metamagnetic response suggests potential for engineering topological spin textures in rare-earth based spintronic devices.
{"title":"Field-induced metamagnetism and topological Hall effect in antiferromagnetic semimetal CeSbTe","authors":"Junbo Li , Yihao Wang , Zhihao Li , Liang Cao , Yimin Xiong","doi":"10.1016/j.jmmm.2025.173682","DOIUrl":"10.1016/j.jmmm.2025.173682","url":null,"abstract":"<div><div>The tunability of electronic band topology and properties by magnetic fields is of great interest for both the exploration of novel states of matter and potential applications. In the topological semimetal CeSbTe, various topological bands and magnetic structures are predicted when a magnetic field is applied along distinct crystallographic directions, particularly within the <span><math><mrow><mi>a</mi><mi>b</mi></mrow></math></span>-plane. Here, we establish the in-plane (H <span><math><mo>∥</mo></math></span> <span><math><mrow><mi>a</mi><mi>b</mi></mrow></math></span>-plane) magnetic phase diagram of CeSbTe using direct current (DC) and alternating current (AC) susceptibility measurements, and electronic transport measurements. An angle-dependent intermediate metamagnetic (IMM) phase is observed at applied fields between 2 and 3 T, suggesting the presence of competing magnetic interactions within its tetragonal Ce<span><math><msup><mrow></mrow><mrow><mn>3</mn><mo>+</mo></mrow></msup></math></span> lattice. The observation of a topological Hall effect in the IMM phase below the Néel temperature, manifesting as a hump-like anomaly in the Hall resistivity, provides evidence for the emergence of nontrivial spin configurations. We propose that a canted antiferromagnetic state forms in this IMM phase, arising from the nontrivial spin texture during the field-induced spin-flop transition. Our study provides critical insights into competing exchange interactions in tetragonal Ce-based systems, while the tunable metamagnetic response suggests potential for engineering topological spin textures in rare-earth based spintronic devices.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"636 ","pages":"Article 173682"},"PeriodicalIF":3.0,"publicationDate":"2025-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145526987","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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