Pub Date : 2026-01-14DOI: 10.1016/j.jmmm.2026.173827
J.M. Martínez , J.M. Nieto-Jalil , A. Lobo Guerrero , J.H. García Gallegos
We present a fast magnetometry route to quantify dipolar mean-field coupling and recover the intrinsic switching-field distribution (iSFD) using only a major hysteresis loop plus the initial magnetization curve acquired from an AC-demagnetized state. Within a Stoner–Wohlfarth/Preisach mean-field picture, interaction-induced shearing broadens susceptibilities; α is obtained from area identities at high remanence and, for low-remanence systems, from an offset-free derivative estimator. Validation on Sr-hexaferrite nanoparticles embedded in PVA nanofibers yields and − 840 Oe for 1.5%, 2.0% and 2.5% loadings, respectively, and deshearing collapses loops and susceptibilities onto their intrinsic references. The workflow includes two internal consistency checks, post-deshearing antisymmetry of branches and initial-curve/upper-branch overlap for , making the estimate auditable. Compared to /Henkel and FORC, the method requires a single loop plus one initial curve and remains robust in the presence of reversible contributions.
{"title":"Quantifying dipolar mean-field interactions from hysteresis and initial curves: A fast Magnetometry route to iSFD Deshearing","authors":"J.M. Martínez , J.M. Nieto-Jalil , A. Lobo Guerrero , J.H. García Gallegos","doi":"10.1016/j.jmmm.2026.173827","DOIUrl":"10.1016/j.jmmm.2026.173827","url":null,"abstract":"<div><div>We present a fast magnetometry route to quantify dipolar mean-field coupling <span><math><mfenced><mi>α</mi></mfenced></math></span> and recover the intrinsic switching-field distribution (iSFD) using only a major hysteresis loop plus the initial magnetization curve acquired from an AC-demagnetized state. Within a Stoner–Wohlfarth/Preisach mean-field picture, interaction-induced shearing broadens susceptibilities; α is obtained from area identities at high remanence and, for low-remanence systems, from an offset-free derivative estimator. Validation on Sr-hexaferrite nanoparticles embedded in PVA nanofibers yields <span><math><mi>α</mi><mo>≈</mo><mo>−</mo><mn>535</mn><mo>,</mo><mo>−</mo><mn>740</mn></math></span> and − 840 Oe for 1.5%, 2.0% and 2.5% loadings, respectively, and deshearing collapses loops and susceptibilities onto their intrinsic references. The workflow includes two internal consistency checks, post-deshearing antisymmetry of branches and initial-curve/upper-branch overlap for <span><math><mi>H</mi><mo>≥</mo><mn>0</mn></math></span>, making the estimate auditable. Compared to <span><math><mi>Δ</mi><mi>M</mi></math></span>/Henkel and FORC, the method requires a single loop plus one initial curve and remains robust in the presence of reversible contributions.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"641 ","pages":"Article 173827"},"PeriodicalIF":3.0,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146073680","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 : 2026-01-14DOI: 10.1016/j.jmmm.2026.173839
Zhixin Shu , Jiaying Jin , Liang Zhou , Boyu Li , Jifei Hong , Dong Ma , Wang Chen , Mi Yan
High-Ce-substituted Nd-Ce-Fe-B permanent magnets offer a cost-effective solution but are limited by magnetic dilution and microstructural degradation. This study specifically investigates the Ce-75 sintered magnets (Ce/total rare earth = 75 wt%) using a dual-modification approach that combines the intergranular addition of (Nd, Pr)Hx and (Nd, Pr)90Dy10Hx with optimized two-step annealing. The 4 wt% (Nd, Pr)Hx-modified magnet achieves a 54% coercivity improvement from 5.48 to 8.45 kOe via the formation of Nd/Pr-rich shell. More remarkably, the 4 wt% (Nd, Pr)90Dy10Hx-modified counterpart demonstrates a 90% enhancement from 5.48 to 10.36 kOe with minimal remanence sacrifice, attributed to synergistic effects of Dy-rich grain shells coupled with Nd/Pr-rich grain boundaries. These findings demonstrate the significance of controlled elemental spatial distribution for achieving simultaneous coercivity enhancement and efficient rare earth utilization.
{"title":"Enhanced coercivity in high-Ce-substituted Nd-Ce-Fe-B magnets via intergranular addition and optimized annealing","authors":"Zhixin Shu , Jiaying Jin , Liang Zhou , Boyu Li , Jifei Hong , Dong Ma , Wang Chen , Mi Yan","doi":"10.1016/j.jmmm.2026.173839","DOIUrl":"10.1016/j.jmmm.2026.173839","url":null,"abstract":"<div><div>High-Ce-substituted Nd-Ce-Fe-B permanent magnets offer a cost-effective solution but are limited by magnetic dilution and microstructural degradation. This study specifically investigates the Ce-75 sintered magnets (Ce/total rare earth = 75 wt%) using a dual-modification approach that combines the intergranular addition of (Nd, Pr)H<sub>x</sub> and (Nd, Pr)<sub>90</sub>Dy<sub>10</sub>H<sub>x</sub> with optimized two-step annealing. The 4 wt% (Nd, Pr)H<sub>x</sub>-modified magnet achieves a 54% coercivity improvement from 5.48 to 8.45 kOe via the formation of Nd/Pr-rich shell. More remarkably, the 4 wt% (Nd, Pr)<sub>90</sub>Dy<sub>10</sub>H<sub>x</sub>-modified counterpart demonstrates a 90% enhancement from 5.48 to 10.36 kOe with minimal remanence sacrifice, attributed to synergistic effects of Dy-rich grain shells coupled with Nd/Pr-rich grain boundaries. These findings demonstrate the significance of controlled elemental spatial distribution for achieving simultaneous coercivity enhancement and efficient rare earth utilization.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"641 ","pages":"Article 173839"},"PeriodicalIF":3.0,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146035354","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 : 2026-01-14DOI: 10.1016/j.jmmm.2026.173840
Jie Xing , Feng Ye , Daniel Duong , Sai Mu , Max T. Pan , Rongying Jin
Complex magnetic materials are extremely attractive for revealing unconventional spin states and novel magnetic excitations. Here, we report the structural, thermodynamic, and magnetic properties of a novel magnetic material Li2Co3Se4O12 based on x-ray and neutron diffraction, specific heat, magnetization, and x-ray photoelectron spectroscopy measurements. X-ray and neutron diffraction refinements reveal two Co sites Co (1) and Co (2) even though both are in the octahedral environment. While they are not connected along the b and c directions, these octahedra are edge-shared forming the Co (2) – Co (1) – Co (2) trimer chain along the a direction. The magnetic susceptibility exhibits the Curie-Weiss (CW) temperature dependence at high temperatures (above ∼50 K) with the negative CW temperature, a dip centered at T⁎ ∼ 8.0 K, and an antiferromagnetic transition at TN = 3.3 K. The specific heat confirms that there is a phase transition at TN and a hump at T⁎. The long-range magnetic transition at TN implies that, in addition to the intra-chain interaction, there is strong inter-chain interaction, which is likely due to polarized SeO3 bridging between chains. Single crystal neutron diffraction refinement reveals a complex magnetic structure with the angle between Co (1) and Co (2) moments ∼105°. Within the Co (2) – Co (1) – Co (2) trimer, two Co (2) moments are parallelly aligned. Surprisingly, the Co (1) moment (1.92μB) is only half of the Co (2) moment (3.96μB). There is likely the spin-state change for Co (1) from the high-spin state at T > T⁎ to the low-spin state at T < T⁎, causing a dip in the magnetic susceptibility and a hump in the specific heat. When the magnetic field is applied, multiple metamagnetic transitions are found in all directions, implying field-driven magnetic excitations. Our results demonstrate rich magnetic properties of Li2Co3Se4O12 that are sensitive to the external stimuli such as the magnetic field.
{"title":"Complex spin structure in co-trimer-chain Li2Co3Se4O12","authors":"Jie Xing , Feng Ye , Daniel Duong , Sai Mu , Max T. Pan , Rongying Jin","doi":"10.1016/j.jmmm.2026.173840","DOIUrl":"10.1016/j.jmmm.2026.173840","url":null,"abstract":"<div><div>Complex magnetic materials are extremely attractive for revealing unconventional spin states and novel magnetic excitations. Here, we report the structural, thermodynamic, and magnetic properties of a novel magnetic material Li<sub>2</sub>Co<sub>3</sub>Se<sub>4</sub>O<sub>12</sub> based on x-ray and neutron diffraction, specific heat, magnetization, and x-ray photoelectron spectroscopy measurements. X-ray and neutron diffraction refinements reveal two Co sites Co (1) and Co (2) even though both are in the octahedral environment. While they are not connected along the <em>b</em> and <em>c</em> directions, these octahedra are edge-shared forming the Co (2) – Co (1) – Co (2) trimer chain along the <em>a</em> direction. The magnetic susceptibility exhibits the Curie-Weiss (CW) temperature dependence at high temperatures (above ∼50 K) with the negative CW temperature, a dip centered at T<sup>⁎</sup> ∼ 8.0 K, and an antiferromagnetic transition at T<sub>N</sub> = 3.3 K. The specific heat confirms that there is a phase transition at T<sub>N</sub> and a hump at T<sup>⁎</sup>. The long-range magnetic transition at T<sub>N</sub> implies that, in addition to the intra-chain interaction, there is strong inter-chain interaction, which is likely due to polarized SeO<sub>3</sub> bridging between chains. Single crystal neutron diffraction refinement reveals a complex magnetic structure with the angle between Co (1) and Co (2) moments ∼105°. Within the Co (2) – Co (1) – Co (2) trimer, two Co (2) moments are parallelly aligned. Surprisingly, the Co (1) moment (1.92μ<sub>B</sub>) is only half of the Co (2) moment (3.96μ<sub>B</sub>). There is likely the spin-state change for Co (1) from the high-spin state at T > T<sup>⁎</sup> to the low-spin state at T < T<sup>⁎</sup>, causing a dip in the magnetic susceptibility and a hump in the specific heat. When the magnetic field is applied, multiple metamagnetic transitions are found in all directions, implying field-driven magnetic excitations. Our results demonstrate rich magnetic properties of Li<sub>2</sub>Co<sub>3</sub>Se<sub>4</sub>O<sub>12</sub> that are sensitive to the external stimuli such as the magnetic field.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"641 ","pages":"Article 173840"},"PeriodicalIF":3.0,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146035353","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 : 2026-01-14DOI: 10.1016/j.jmmm.2026.173838
Lichun Zhan , Wenyu Pan , Ruihua Du , Weiqiang Liu , Zan Long , Shengli Jia , Qifeng Wei , Xiongfei Wu , Ming Yue
Laser cutting, recognized for its narrow kerf, high efficiency, and adaptability to complex geometries, is increasingly employed in the machining of thin sintered Nd–Fe–B magnets. This work systematically evaluates the influence of laser cutting versus conventional multi-wire cutting combined with grinding on the microstructure, mechanical strength, and magnetic properties of magnets under black, chamfered, and pickled conditions. Laser cutting induces stepped demagnetization curves, lowers intrinsic coercivity and mechanical properties compared to conventional multi-wire cutting combined with grinding method. Results indicate that chamfering improves the three-point bending force of laser-cut samples by approximately 31.4% on average. After pickling, the specific magnetic moment of laser-cut samples is only 0.13% lower, and the irreversible flux loss is merely 0.08% higher than that of ground specimens. Microstructural analysis reveals that laser-cut surfaces contain a resolidified layer, micropores, and networked microcracks, which contribute to the degradation in mechanical and magnetic properties. Magnetic domain observations further demonstrate that laser-cut black samples exhibit blurred domain boundaries and maze domains, whereas chamfered specimens show a marked reduction in maze domains and improved domain alignment. Under identical reverse magnetic fields, domain reversal occurs more readily in black samples than in chamfered ones. In summary, through appropriate parameter selection and post-processing, such as chamfering and pickling, the mechanical and magnetic performance of laser-cut thin Nd-Fe-B magnets can closely match that of ground magnets, offering valuable guidance for process optimization in thin magnet manufacturing.
{"title":"Effects of laser cutting and post-processing on the microstructure and properties of thin sintered Nd-Fe-B magnets","authors":"Lichun Zhan , Wenyu Pan , Ruihua Du , Weiqiang Liu , Zan Long , Shengli Jia , Qifeng Wei , Xiongfei Wu , Ming Yue","doi":"10.1016/j.jmmm.2026.173838","DOIUrl":"10.1016/j.jmmm.2026.173838","url":null,"abstract":"<div><div>Laser cutting, recognized for its narrow kerf, high efficiency, and adaptability to complex geometries, is increasingly employed in the machining of thin sintered Nd–Fe–B magnets. This work systematically evaluates the influence of laser cutting versus conventional multi-wire cutting combined with grinding on the microstructure, mechanical strength, and magnetic properties of magnets under black, chamfered, and pickled conditions. Laser cutting induces stepped demagnetization curves, lowers intrinsic coercivity and mechanical properties compared to conventional multi-wire cutting combined with grinding method. Results indicate that chamfering improves the three-point bending force of laser-cut samples by approximately 31.4% on average. After pickling, the specific magnetic moment of laser-cut samples is only 0.13% lower, and the irreversible flux loss is merely 0.08% higher than that of ground specimens. Microstructural analysis reveals that laser-cut surfaces contain a resolidified layer, micropores, and networked microcracks, which contribute to the degradation in mechanical and magnetic properties. Magnetic domain observations further demonstrate that laser-cut black samples exhibit blurred domain boundaries and maze domains, whereas chamfered specimens show a marked reduction in maze domains and improved domain alignment. Under identical reverse magnetic fields, domain reversal occurs more readily in black samples than in chamfered ones. In summary, through appropriate parameter selection and post-processing, such as chamfering and pickling, the mechanical and magnetic performance of laser-cut thin Nd-Fe-B magnets can closely match that of ground magnets, offering valuable guidance for process optimization in thin magnet manufacturing.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"641 ","pages":"Article 173838"},"PeriodicalIF":3.0,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974635","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}
Two-dimensional (2D) magnetic tunnel junctions (MTJs) based on van der Waals heterostructures, as core spintronics devices, offer high storage density and fast information processing capabilities. However, the influences of intrinsic point defects on their Tunneling Magneto-resistance (TMR) effects as well as physical mechanisms remain underexplored. Here, we design a Cu(111)|CrBr3|WS2|CrBr3|Cu(111) MTJ utilizing first-principles calculations combined with the nonequilibrium Green's function method. The perfect MTJ exhibits near 100% spin polarization and an ultrahigh TMR of 4312.77%; it maintains TMR above 1000% and high spin filtering efficiency within a bias voltage range from −0.5 to 0.5 V. To investigate the factors contributing to the low TMR in experimentally fabricated MTJs, we systematically investigated the impact of point defects (intrinsic vacancies/substitutions) on CrBr3|WS2|CrBr3 MTJ performance. Spin-polarized electron transport channels are modified by point defects. S and Br vacancies show negligible effects on TMR. While W and Cr vacancies enhance spin-down electron transmission in parallel magnetization configurations, thereby reducing TMR. Substituting S atoms with Br atoms significantly improves TMR to 6916.36%. The work highlights defect engineering as a viable approach to optimize 2D MTJ performance, offering theoretical insights for designing high-efficiency spintronic devices with enhanced stability and tunability.
{"title":"Modulation of spin transport in CrBr3|WS2|CrBr3 magnetic tunnel junctions via point defects","authors":"Yongsheng Zhao , Yuxin Zhang , Haishan Zhang, Juan Lyu, Jian Gong, Shaoqiang Guo","doi":"10.1016/j.jmmm.2026.173837","DOIUrl":"10.1016/j.jmmm.2026.173837","url":null,"abstract":"<div><div>Two-dimensional (2D) magnetic tunnel junctions (MTJs) based on van der Waals heterostructures, as core spintronics devices, offer high storage density and fast information processing capabilities. However, the influences of intrinsic point defects on their Tunneling Magneto-resistance (TMR) effects as well as physical mechanisms remain underexplored. Here, we design a Cu(111)|CrBr<sub>3</sub>|WS<sub>2</sub>|CrBr<sub>3</sub>|Cu(111) MTJ utilizing first-principles calculations combined with the nonequilibrium Green's function method. The perfect MTJ exhibits near 100% spin polarization and an ultrahigh TMR of 4312.77%; it maintains TMR above 1000% and high spin filtering efficiency within a bias voltage range from −0.5 to 0.5 V. To investigate the factors contributing to the low TMR in experimentally fabricated MTJs, we systematically investigated the impact of point defects (intrinsic vacancies/substitutions) on CrBr<sub>3</sub>|WS<sub>2</sub>|CrBr<sub>3</sub> MTJ performance. Spin-polarized electron transport channels are modified by point defects. S and Br vacancies show negligible effects on TMR. While W and Cr vacancies enhance spin-down electron transmission in parallel magnetization configurations, thereby reducing TMR. Substituting S atoms with Br atoms significantly improves TMR to 6916.36%. The work highlights defect engineering as a viable approach to optimize 2D MTJ performance, offering theoretical insights for designing high-efficiency spintronic devices with enhanced stability and tunability.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"641 ","pages":"Article 173837"},"PeriodicalIF":3.0,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146035295","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 : 2026-01-12DOI: 10.1016/j.jmmm.2026.173835
Jhon J. Melo Quintero , Azucena M. Mudarra Navarro , Victoria I. Fernández , C.E. Rodríguez Torres , Leonardo A. Errico
Ferrites (spinel structure, MFe2O4) are one of the richest and most studied oxide groups due to their multiple and interesting physical properties and wide applications. Particularly, Zn2+Fe3+2O4 has been largely studied but its magnetic structure is still unresolved. To contribute to the understanding of its magnetic nature we present here a theoretical study of the role of defects (oxygen vacancies, cationic inversion) on the magnetic interactions in Zn-ferrite. ZnFe2O4 adopts the normal spinel structure where Zn2+ cations are placed at the 8a tetrahedral (A) sites and Fe3+ populates the 16d octahedral (B) sites. Using first-principles calculations based on Density Functional Theory (DFT) and the supercell approach, the energy of multiple magnetic configurations for reduced (ZnFe2O4-δ), partially inverted, (Zn1-xFex)[ZnxFe2-x]O4, and partially inverted and reduced, (Zn1-xFex)[ZnxFe2-x]O4-δ, Zn-ferrite were calculated and then mapped to a classical Heisenberg spin model to obtain the magnetic exchange couplings Jn up to fifth neighbours. Compared with pristine and normal ZnFe2O4, where the interactions Fe(site B)–Fe(site B) up to fifth neighbours (JBBi) are antiferromagnetic, in the case of ZnFe2O4-δ the interaction at second neighbours is ferromagnetic. In the case of (Zn1-xFex)[Fe2-xZnx]O4 and (Zn1-xFex)[ZnxFe2-x]O4-δ the interactions Fe(site A)-Fe(site B) resulted to be significantly stronger than JBBi. Moreover, the first-neighbour interaction is predicted to be ferromagnetic, while at second neighbours it is antiferromagnetic and dominant. Our results show that ZnFe2O4 constitutes a delicate magnetic system, where competing magnetic interactions can be easily affected by defects and highlight its crucial role in promoting different magnetic responses, enabling us to explain the ferrimagnetic response observed at room-temperature in ZnFe2O4 nanoparticles and thin films.
{"title":"Magnetic interactions in defective ZnFe2O4. A density functional theory study","authors":"Jhon J. Melo Quintero , Azucena M. Mudarra Navarro , Victoria I. Fernández , C.E. Rodríguez Torres , Leonardo A. Errico","doi":"10.1016/j.jmmm.2026.173835","DOIUrl":"10.1016/j.jmmm.2026.173835","url":null,"abstract":"<div><div>Ferrites (spinel structure, MFe<sub>2</sub>O<sub>4</sub>) are one of the richest and most studied oxide groups due to their multiple and interesting physical properties and wide applications. Particularly, Zn<sup>2+</sup>Fe<sup>3+</sup><sub>2</sub>O<sub>4</sub> has been largely studied but its magnetic structure is still unresolved. To contribute to the understanding of its magnetic nature we present here a theoretical study of the role of defects (oxygen vacancies, cationic inversion) on the magnetic interactions in Zn-ferrite. ZnFe<sub>2</sub>O<sub>4</sub> adopts the normal spinel structure where Zn<sup>2+</sup> cations are placed at the <em>8a</em> tetrahedral (<em>A</em>) sites and Fe<sup>3+</sup> populates the <em>16d</em> octahedral (<em>B</em>) sites. Using first-principles calculations based on Density Functional Theory (DFT) and the supercell approach, the energy of multiple magnetic configurations for reduced (ZnFe<sub>2</sub>O<sub>4-<em>δ</em></sub>), partially inverted, (Zn<sub>1-<em>x</em></sub>Fe<sub><em>x</em></sub>)[Zn<sub><em>x</em></sub>Fe<sub>2-<em>x</em></sub>]O<sub>4</sub>, and partially inverted and reduced, (Zn<sub>1-<em>x</em></sub>Fe<sub><em>x</em></sub>)[Zn<sub><em>x</em></sub>Fe<sub>2-<em>x</em></sub>]O<sub>4-<em>δ</em></sub>, Zn-ferrite were calculated and then mapped to a classical Heisenberg spin model to obtain the magnetic exchange couplings <em>J</em><sub><em>n</em></sub> up to fifth neighbours. Compared with pristine and normal ZnFe<sub>2</sub>O<sub>4</sub>, where the interactions Fe(site B)–Fe(site B) up to fifth neighbours (<em>J</em><sup><em>BB</em></sup><sub><em>i</em></sub>) are antiferromagnetic, in the case of ZnFe<sub>2</sub>O<sub>4-<em>δ</em></sub> the interaction at second neighbours is ferromagnetic. In the case of (Zn<sub>1-<em>x</em></sub>Fe<sub><em>x</em></sub>)[Fe<sub>2-<em>x</em></sub>Zn<em>x</em>]O<sub>4</sub> and (Zn<sub>1-<em>x</em></sub>Fe<sub><em>x</em></sub>)[Zn<sub><em>x</em></sub>Fe<sub>2-<em>x</em></sub>]O<sub>4-<em>δ</em></sub> the interactions Fe(site A)-Fe(site B) resulted to be significantly stronger than <em>J</em><sup><em>BB</em></sup><sub><em>i</em></sub>. Moreover, the first-neighbour interaction is predicted to be ferromagnetic, while at second neighbours it is antiferromagnetic and dominant. Our results show that ZnFe<sub>2</sub>O<sub>4</sub> constitutes a delicate magnetic system, where competing magnetic interactions can be easily affected by defects and highlight its crucial role in promoting different magnetic responses, enabling us to explain the ferrimagnetic response observed at room-temperature in ZnFe<sub>2</sub>O<sub>4</sub> nanoparticles and thin films.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"641 ","pages":"Article 173835"},"PeriodicalIF":3.0,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145975170","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 : 2026-01-12DOI: 10.1016/j.jmmm.2026.173832
Gorachand Biswal , Babita Ojha , Varsa Purohit , Rakesh Ranjan Sahoo , Dhrubananda Behera , Deba Nirmalya Das
The ferrite samples Mg0.5Mn0.5Fe2-xErxO4 (x = 0, 0.02, 0.04, 0.06, 0.1) prepared using the solid-state route were evaluated for microwave absorption applications. X-ray diffraction with Rietveld refinement revealed multiphase characteristics and the coexistence of a spinel phase with an orthorhombic phase attributed to the larger Er3+ ionic radius. The SEM analysis of rare earth-doped spinel ferrites reveals that grain size and porosity are significantly influenced by doping concentration, which in turn strongly affect the dielectric and magnetic properties. AFM indicated high surface roughness. The favourable figures of dielectric constant and loss factor recorded at frequency variation makes the material suitable in high frequency performances. The Er modified ferrites possessing a broad range of relaxation period can interact and effectively absorb an extended range of spectrum from the microwave frequency range. UV–Vis spectroscopy demonstrated an increase in the optical forbidden band gap from 1.06 eV to 2.30 eV after doping of erbium, enhancing light absorption. The combined improvements in optical, dielectric, and thermal properties confirm that Er-modified ferrites are promising candidates for high-frequency, high-temperature microwave absorbing applications. The increase of coercivity with respect to doping concentration may be attributed to the anisotropy due to the strong spin orbit coupling of Er3+.
{"title":"Improvement in magnetic, optical and dielectric behavior on erbium addition to Mg0.5Mn0.5Fe2O4 for device applications","authors":"Gorachand Biswal , Babita Ojha , Varsa Purohit , Rakesh Ranjan Sahoo , Dhrubananda Behera , Deba Nirmalya Das","doi":"10.1016/j.jmmm.2026.173832","DOIUrl":"10.1016/j.jmmm.2026.173832","url":null,"abstract":"<div><div>The ferrite samples Mg<sub>0.5</sub>Mn<sub>0.5</sub>Fe<sub>2-x</sub>Er<sub>x</sub>O<sub>4</sub> (x = 0, 0.02, 0.04, 0.06, 0.1) prepared using the solid-state route were evaluated for microwave absorption applications. X-ray diffraction with Rietveld refinement revealed multiphase characteristics and the coexistence of a spinel phase with an orthorhombic phase attributed to the larger Er<sup>3+</sup> ionic radius. The SEM analysis of rare earth-doped spinel ferrites reveals that grain size and porosity are significantly influenced by doping concentration, which in turn strongly affect the dielectric and magnetic properties. AFM indicated high surface roughness. The favourable figures of dielectric constant and loss factor recorded at frequency variation makes the material suitable in high frequency performances. The Er modified ferrites possessing a broad range of relaxation period can interact and effectively absorb an extended range of spectrum from the microwave frequency range. UV–Vis spectroscopy demonstrated an increase in the optical forbidden band gap from 1.06 eV to 2.30 eV after doping of erbium, enhancing light absorption. The combined improvements in optical, dielectric, and thermal properties confirm that Er-modified ferrites are promising candidates for high-frequency, high-temperature microwave absorbing applications. The increase of coercivity with respect to doping concentration may be attributed to the anisotropy due to the strong spin orbit coupling of Er<sup>3+</sup>.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"641 ","pages":"Article 173832"},"PeriodicalIF":3.0,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146035303","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 : 2026-01-12DOI: 10.1016/j.jmmm.2026.173834
Hanji Zhu , Baoming Gong , Yunfeng Zhao , Caiyan Deng , Yong Liu
In this study, full-scale hydrostatic experiments were performed on a pipeline to investigate the behavior of the magnetic flux under varying internal pressures and sensor lift-off distances. Full-field strain distribution with finite element modeling was used to characterize the stress–strain condition at the girth weld. A comprehensive investigation was conducted into the behavior of triaxial magnetic flux signals and their mechanical responses. A novel magnetic parameter, Beff, was proposed based on correlation analysis of multiple signal types and was experimentally validated. The influence of lift-off distance on Beff was discussed, and the underlying mechanism behind environmental magnetic interference was uncovered. Building upon these findings, a robust empirical model was proposed for the quantitative assessment of stress states in buried pipelines. The results are instructive for the application of metal magnetic memory (MMM) technology in non-contact pipeline health monitoring.
{"title":"Quantitative stress modeling in full-scale pipelines via dual-probe differential magneto-mechanical coupling technique","authors":"Hanji Zhu , Baoming Gong , Yunfeng Zhao , Caiyan Deng , Yong Liu","doi":"10.1016/j.jmmm.2026.173834","DOIUrl":"10.1016/j.jmmm.2026.173834","url":null,"abstract":"<div><div>In this study, full-scale hydrostatic experiments were performed on a pipeline to investigate the behavior of the magnetic flux under varying internal pressures and sensor lift-off distances. Full-field strain distribution with finite element modeling was used to characterize the stress–strain condition at the girth weld. A comprehensive investigation was conducted into the behavior of triaxial magnetic flux signals and their mechanical responses. A novel magnetic parameter, <em>B</em><sub>eff</sub>, was proposed based on correlation analysis of multiple signal types and was experimentally validated. The influence of lift-off distance on <em>B</em><sub>eff</sub> was discussed, and the underlying mechanism behind environmental magnetic interference was uncovered. Building upon these findings, a robust empirical model was proposed for the quantitative assessment of stress states in buried pipelines. The results are instructive for the application of metal magnetic memory (MMM) technology in non-contact pipeline health monitoring.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"641 ","pages":"Article 173834"},"PeriodicalIF":3.0,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145975168","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 : 2026-01-11DOI: 10.1016/j.jmmm.2026.173813
Hanzhi Liu , Yibing Zhao , Jie Xu , Bokai Liang , Ying Jin , Changjun Jiang
The magnon-magnon coupling in single-layer patterned magnetic thin films holds promise for providing a theoretical foundation and guiding the development of low-power quantum information processing chips based on magnons. In this work, we designed and fabricated periodic arrays of CoFeB stripes. The pinning effect of stripe edges on magnetic moments leads to the excitation of the edge mode, whose dispersion relation exhibits degeneracy with that of the bulk mode, generating an anti-crossing gap that evolves regularly with magnetic field orientation. Furthermore, the hybridization frequency and coupling strength between the edge and bulk modes can be effectively modulated by adjusting the stripe width and thickness. This phenomenon primarily arises from the modulation of the stripe's shape anisotropy by geometric parameters, which consequently governs the magnetization components along different directions within the stripes under externally applied magnetic fields.
{"title":"Spin wave hybridization in periodic array of CoFeB stripes","authors":"Hanzhi Liu , Yibing Zhao , Jie Xu , Bokai Liang , Ying Jin , Changjun Jiang","doi":"10.1016/j.jmmm.2026.173813","DOIUrl":"10.1016/j.jmmm.2026.173813","url":null,"abstract":"<div><div>The magnon-magnon coupling in single-layer patterned magnetic thin films holds promise for providing a theoretical foundation and guiding the development of low-power quantum information processing chips based on magnons. In this work, we designed and fabricated periodic arrays of CoFeB stripes. The pinning effect of stripe edges on magnetic moments leads to the excitation of the edge mode, whose dispersion relation exhibits degeneracy with that of the bulk mode, generating an anti-crossing gap that evolves regularly with magnetic field orientation. Furthermore, the hybridization frequency and coupling strength between the edge and bulk modes can be effectively modulated by adjusting the stripe width and thickness. This phenomenon primarily arises from the modulation of the stripe's shape anisotropy by geometric parameters, which consequently governs the magnetization components along different directions within the stripes under externally applied magnetic fields.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"641 ","pages":"Article 173813"},"PeriodicalIF":3.0,"publicationDate":"2026-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145975218","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 : 2026-01-11DOI: 10.1016/j.jmmm.2026.173833
Muhammad Luqman Hashmi , Fabio Scaffidi Muta , Gianluca Deninno , C. Parmar , R. Verma , F. Mazaleyrat , Shashank N. Kane , Salil Modak , V.R. Reddy , Paola Maria Tiberto , Marco Coïsson
This research investigated the effects of solution pH during synthesis and annealing on the structural, magnetic, optical, and dielectric properties of MgFe2O4 synthesised using the citric acid-assisted sol-gel auto-combustion method. Structural data showed that crystallinity, lattice parameters, and cation distribution were strongly influenced by both pH and annealing temperature. Optimal morphology and crystallinity were achieved at pH 7 and an annealing temperature of 550 °C for 3 h, under which cation ordering and defect reduction were effectively achieved. Magnetic characterisation revealed a significant improvement in saturation magnetisation (20.6 emu/g) under optimal conditions, attributed to increased super-exchange interactions. The optical bandgap was modulated by more than 11% (2.04 to 2.30 eV) by adjusting pH-mediated surface chemistry and subsequent defect states. The sample synthesised at pH 9 exhibited the highest values of ε’, ε”, and σac. These results conclusively demonstrate that accurate control of synthesis pH and annealing enables the design of multifunctional properties in MgFe2O4 nanoparticles, providing a solid foundation for their application in high-end magnetic, optical, and electronic devices.
{"title":"Engineering MgFe2O4 nanoparticles to enhance magnetic, optical, and dielectric performance","authors":"Muhammad Luqman Hashmi , Fabio Scaffidi Muta , Gianluca Deninno , C. Parmar , R. Verma , F. Mazaleyrat , Shashank N. Kane , Salil Modak , V.R. Reddy , Paola Maria Tiberto , Marco Coïsson","doi":"10.1016/j.jmmm.2026.173833","DOIUrl":"10.1016/j.jmmm.2026.173833","url":null,"abstract":"<div><div>This research investigated the effects of solution pH during synthesis and annealing on the structural, magnetic, optical, and dielectric properties of MgFe<sub>2</sub>O<sub>4</sub> synthesised using the citric acid-assisted sol-gel auto-combustion method. Structural data showed that crystallinity, lattice parameters, and cation distribution were strongly influenced by both pH and annealing temperature. Optimal morphology and crystallinity were achieved at pH 7 and an annealing temperature of 550 °C for 3 h, under which cation ordering and defect reduction were effectively achieved. Magnetic characterisation revealed a significant improvement in saturation magnetisation (20.6 emu/g) under optimal conditions, attributed to increased super-exchange interactions. The optical bandgap was modulated by more than 11% (2.04 to 2.30 eV) by adjusting pH-mediated surface chemistry and subsequent defect states. The sample synthesised at pH 9 exhibited the highest values of <em>ε’</em>, <em>ε”</em>, and <em>σ</em><sub><em>ac</em></sub>. These results conclusively demonstrate that accurate control of synthesis pH and annealing enables the design of multifunctional properties in MgFe<sub>2</sub>O<sub>4</sub> nanoparticles, providing a solid foundation for their application in high-end magnetic, optical, and electronic devices.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"641 ","pages":"Article 173833"},"PeriodicalIF":3.0,"publicationDate":"2026-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145975217","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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