Pub Date : 2025-12-04DOI: 10.1109/TMAG.2025.3640177
Xuchao Zhang;Lei Ma;Chao Fan;Hongyun Liu;Yuanyuan Li;Jiting Li;Jian Li;Jiatai Wang
The wireless charging performance of coils inserted with Ni0.2Mn0.2Zn0.6Fe2O4 ferrite cores was investigated. Ni0.2Mn0.2Zn0.6Fe2O4 ferrites were prepared and sintered under different temperatures ($T_{mathrm{s}}$ ). The effects of $T_{mathrm{s}}$ on the crystal structure, phase composition, morphology, magnetic properties, and wireless charging performance were investigated. The X-ray diffraction (XRD) measurements reveal that there are two phases including an $alpha-mathrm{Fe}_2 mathrm{O}_3$ stray phase. As $T_{mathrm{s}}$ increasing from $700^{circ} mathrm{C}$ to $1100^{circ} mathrm{C}, alpha-mathrm{Fe}_2 mathrm{O}_3$ stray phase disappeared and formed a single spinel phase. The grain size and saturated magnetization ($M_{mathrm{s}}$ ) of ferrites also increase with $T_{mathrm{s}}$ , and the coercivity ($H_{mathrm{c}}$ ) decreases with $T_{mathrm{s}}$ . These are all correlated with the improvement of crystal properties and especially the elimination of $alpha-mathrm{Fe}_2 mathrm{O}_3$ stray phases. Wireless charging results show that the $1000^{circ} mathrm{C}$ sintered ferrite has the highest influence on the charging efficiency.
{"title":"Sintered Ni–Mn–Zn Ferrites With Changeable Magnetic Properties for Wireless Charging Application","authors":"Xuchao Zhang;Lei Ma;Chao Fan;Hongyun Liu;Yuanyuan Li;Jiting Li;Jian Li;Jiatai Wang","doi":"10.1109/TMAG.2025.3640177","DOIUrl":"https://doi.org/10.1109/TMAG.2025.3640177","url":null,"abstract":"The wireless charging performance of coils inserted with Ni0.2Mn0.2Zn0.6Fe2O4 ferrite cores was investigated. Ni0.2Mn0.2Zn0.6Fe2O4 ferrites were prepared and sintered under different temperatures (<inline-formula> <tex-math>$T_{mathrm{s}}$ </tex-math></inline-formula>). The effects of <inline-formula> <tex-math>$T_{mathrm{s}}$ </tex-math></inline-formula> on the crystal structure, phase composition, morphology, magnetic properties, and wireless charging performance were investigated. The X-ray diffraction (XRD) measurements reveal that there are two phases including an <inline-formula> <tex-math>$alpha-mathrm{Fe}_2 mathrm{O}_3$ </tex-math></inline-formula> stray phase. As <inline-formula> <tex-math>$T_{mathrm{s}}$ </tex-math></inline-formula> increasing from <inline-formula> <tex-math>$700^{circ} mathrm{C}$ </tex-math></inline-formula> to <inline-formula> <tex-math>$1100^{circ} mathrm{C}, alpha-mathrm{Fe}_2 mathrm{O}_3$ </tex-math></inline-formula> stray phase disappeared and formed a single spinel phase. The grain size and saturated magnetization (<inline-formula> <tex-math>$M_{mathrm{s}}$ </tex-math></inline-formula>) of ferrites also increase with <inline-formula> <tex-math>$T_{mathrm{s}}$ </tex-math></inline-formula>, and the coercivity (<inline-formula> <tex-math>$H_{mathrm{c}}$ </tex-math></inline-formula>) decreases with <inline-formula> <tex-math>$T_{mathrm{s}}$ </tex-math></inline-formula>. These are all correlated with the improvement of crystal properties and especially the elimination of <inline-formula> <tex-math>$alpha-mathrm{Fe}_2 mathrm{O}_3$ </tex-math></inline-formula> stray phases. Wireless charging results show that the <inline-formula> <tex-math>$1000^{circ} mathrm{C}$ </tex-math></inline-formula> sintered ferrite has the highest influence on the charging efficiency.","PeriodicalId":13405,"journal":{"name":"IEEE Transactions on Magnetics","volume":"62 1","pages":"1-6"},"PeriodicalIF":1.9,"publicationDate":"2025-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145847827","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-04DOI: 10.1109/TMAG.2025.3640276
Andreas Grendas;Michael Wiesheu;Sebastian Schöps;Benjamin Marussig
Adaptive refinement in isogeometric analysis (IGA) provides a flexible way to improve accuracy while controlling computational effort. This work builds on spline basis functions, used both for geometry representation and numerical discretization, and extends them with truncated hierarchical B-splines (THB-splines) to enable local mesh refinement with structured flexibility. To support standard finite element assembly, multi-level Bézier extraction is applied, allowing THB-spline bases to be expressed in terms of local Bernstein polynomials. Refinement is driven by a least-squares a posteriori error estimator integrated into the spline discretization. A unified formulation is presented that couples this estimator with the harmonic mortaring of the rotor–stator, ensuring consistency of the interface while guiding refinement in the coupled problem. The method is demonstrated with 2-D magnetostatic simulations involving a permanent magnet synchronous machine (PMSM).
{"title":"Adaptive Isogeometric Analysis With THB-Splines and Multi-Level Bézier Extraction for Coupled Magnetostatics","authors":"Andreas Grendas;Michael Wiesheu;Sebastian Schöps;Benjamin Marussig","doi":"10.1109/TMAG.2025.3640276","DOIUrl":"https://doi.org/10.1109/TMAG.2025.3640276","url":null,"abstract":"Adaptive refinement in isogeometric analysis (IGA) provides a flexible way to improve accuracy while controlling computational effort. This work builds on spline basis functions, used both for geometry representation and numerical discretization, and extends them with truncated hierarchical B-splines (THB-splines) to enable local mesh refinement with structured flexibility. To support standard finite element assembly, multi-level Bézier extraction is applied, allowing THB-spline bases to be expressed in terms of local Bernstein polynomials. Refinement is driven by a least-squares a posteriori error estimator integrated into the spline discretization. A unified formulation is presented that couples this estimator with the harmonic mortaring of the rotor–stator, ensuring consistency of the interface while guiding refinement in the coupled problem. The method is demonstrated with 2-D magnetostatic simulations involving a permanent magnet synchronous machine (PMSM).","PeriodicalId":13405,"journal":{"name":"IEEE Transactions on Magnetics","volume":"62 1","pages":"1-11"},"PeriodicalIF":1.9,"publicationDate":"2025-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11278434","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145847834","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We present a method for modeling arbitrarily shaped anisotropic magnetoelectric objects immersed in a homogeneous isotropic medium and exposed to an arbitrary electric field. The method requires the discretization of only boundary layers and solves the problem directly, without transforming it into an isotropic one. We investigate anisotropic magnetoelectric materials of the Tellegen type, characterized by nine parameters for each of the permittivity, permeability, and coupling matrices. Results are compared against an analytical solution for the case of a magnetoelectric anisotropic sphere placed in air and exposed to a uniform electric field. We achieve a total normalized root mean square error (NRMSE) for the electric field below 0.1% and below 0.2% for the magnetic field. With a slight modification, the method can be applied to magnetoelectric materials exposed to a magnetic or combined electric and magnetic fields.
{"title":"Boundary Element Modeling of Magnetoelectric Anisotropic Materials","authors":"Bojana Petković;Marek Ziolkowski;Jens Haueisen;Hannes Toepfer","doi":"10.1109/TMAG.2025.3639930","DOIUrl":"https://doi.org/10.1109/TMAG.2025.3639930","url":null,"abstract":"We present a method for modeling arbitrarily shaped anisotropic magnetoelectric objects immersed in a homogeneous isotropic medium and exposed to an arbitrary electric field. The method requires the discretization of only boundary layers and solves the problem directly, without transforming it into an isotropic one. We investigate anisotropic magnetoelectric materials of the Tellegen type, characterized by nine parameters for each of the permittivity, permeability, and coupling matrices. Results are compared against an analytical solution for the case of a magnetoelectric anisotropic sphere placed in air and exposed to a uniform electric field. We achieve a total normalized root mean square error (NRMSE) for the electric field below 0.1% and below 0.2% for the magnetic field. With a slight modification, the method can be applied to magnetoelectric materials exposed to a magnetic or combined electric and magnetic fields.","PeriodicalId":13405,"journal":{"name":"IEEE Transactions on Magnetics","volume":"62 1","pages":"1-9"},"PeriodicalIF":1.9,"publicationDate":"2025-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145847825","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We propose an oscillation-controlled magnetic sensing (OCMS) circuit architecture using MgO-based magnetic tunnel junctions (MTJs) and investigate its magnetic field response characteristics. Compared to the conventional sensing-current method commonly used in hard disk drive (HDD) read heads and magnetic sensors, the OCMS approach achieves an output voltage up to 8.1 times higher. Notably, a large oscillation output of 952 mVpp is obtained with sensing current as low as 0.4–0.6 mA flowing through the MTJ. The measured output response shows strong agreement with the TopSPICE simulations, which further predict output voltages exceeding 10 Vpp at a sensing current of 0.82 mA and an operation frequency of 10 MHz. These results demonstrate that the OCMS method enables high-output, low-power, and high-frequency magnetic sensing, offering a promising solution for the next-generation spintronic sensor technologies.
{"title":"Magnetic Sensing via Oscillation Control in MgO-Based Magnetic Tunnel Junctions","authors":"Mizuki Wakamoto;Yuto Shibata;Mizuki Matsuzaka;Gang Xiao;Hideo Kaiju","doi":"10.1109/TMAG.2025.3640104","DOIUrl":"https://doi.org/10.1109/TMAG.2025.3640104","url":null,"abstract":"We propose an oscillation-controlled magnetic sensing (OCMS) circuit architecture using MgO-based magnetic tunnel junctions (MTJs) and investigate its magnetic field response characteristics. Compared to the conventional sensing-current method commonly used in hard disk drive (HDD) read heads and magnetic sensors, the OCMS approach achieves an output voltage up to 8.1 times higher. Notably, a large oscillation output of 952 mVpp is obtained with sensing current as low as 0.4–0.6 mA flowing through the MTJ. The measured output response shows strong agreement with the TopSPICE simulations, which further predict output voltages exceeding 10 Vpp at a sensing current of 0.82 mA and an operation frequency of 10 MHz. These results demonstrate that the OCMS method enables high-output, low-power, and high-frequency magnetic sensing, offering a promising solution for the next-generation spintronic sensor technologies.","PeriodicalId":13405,"journal":{"name":"IEEE Transactions on Magnetics","volume":"62 1","pages":"1-7"},"PeriodicalIF":1.9,"publicationDate":"2025-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145847809","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-27DOI: 10.1109/TMAG.2025.3638155
Nicoleta Banu;Massimo Pasquale;Fausto Fiorillo
We show that the time-domain formulation of the dynamic losses in soft magnetic materials provided by the statistical theory of losses (STLs) leads to an accurate analytical prediction of energy loss and hysteresis loops in magnetic sheets and soft ferrites under sinusoidal and non-sinusoidal induction. In its generalized form, this theory applies to both conducting and nonconducting materials by separately treating the dissipation phenomena engendered by eddy currents and spin damping. The equations for the classical and excess loss components and the predicted hysteresis loop dependence on the flux waveform are based on the definition and calculation of the instantaneous values of the classical and excess fields, where the material conductivity and the Landau–Lifshitz constant are the intrinsic parameters involved in damping. Energy loss measurements have been performed at different peak polarization values on Fe-Si [grain-oriented and nonoriented (NO)] and Fe-Co (Vacoflux) sheets up to 400 Hz, and on Mn-Zn ferrites (N87) up to 500 kHz. The effect of distortion introduced by either a third or fifth harmonic component, 0°–180° phase-shifted with respect to the fundamental component, is predicted, with and without minor loops, in the soft magnetic sheets. Instead, the Mn-Zn samples are tested under rectangular symmetric/asymmetric voltage, emulating the working regime of dc–dc buck converters. Whatever the case, the predictive method relies on the STL-based time-domain retrieval of the excess and classical viscous fields. This objective is achieved in ferrites through the theoretical prediction of the energy loss due to the spin-damping mechanism, while the skin effect in metallic sheets poses an effective upper-frequency limitation to the analytical approach.
{"title":"Predicting Energy Loss and Hysteresis Loop Under Non-Sinusoidal Induction in Soft Magnetic Sheets and Ferrites","authors":"Nicoleta Banu;Massimo Pasquale;Fausto Fiorillo","doi":"10.1109/TMAG.2025.3638155","DOIUrl":"https://doi.org/10.1109/TMAG.2025.3638155","url":null,"abstract":"We show that the time-domain formulation of the dynamic losses in soft magnetic materials provided by the statistical theory of losses (STLs) leads to an accurate analytical prediction of energy loss and hysteresis loops in magnetic sheets and soft ferrites under sinusoidal and non-sinusoidal induction. In its generalized form, this theory applies to both conducting and nonconducting materials by separately treating the dissipation phenomena engendered by eddy currents and spin damping. The equations for the classical and excess loss components and the predicted hysteresis loop dependence on the flux waveform are based on the definition and calculation of the instantaneous values of the classical and excess fields, where the material conductivity and the Landau–Lifshitz constant are the intrinsic parameters involved in damping. Energy loss measurements have been performed at different peak polarization values on Fe-Si [grain-oriented and nonoriented (NO)] and Fe-Co (Vacoflux) sheets up to 400 Hz, and on Mn-Zn ferrites (N87) up to 500 kHz. The effect of distortion introduced by either a third or fifth harmonic component, 0°–180° phase-shifted with respect to the fundamental component, is predicted, with and without minor loops, in the soft magnetic sheets. Instead, the Mn-Zn samples are tested under rectangular symmetric/asymmetric voltage, emulating the working regime of dc–dc buck converters. Whatever the case, the predictive method relies on the STL-based time-domain retrieval of the excess and classical viscous fields. This objective is achieved in ferrites through the theoretical prediction of the energy loss due to the spin-damping mechanism, while the skin effect in metallic sheets poses an effective upper-frequency limitation to the analytical approach.","PeriodicalId":13405,"journal":{"name":"IEEE Transactions on Magnetics","volume":"62 2","pages":"1-13"},"PeriodicalIF":1.9,"publicationDate":"2025-11-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11270955","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146082300","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-26DOI: 10.1109/TMAG.2025.3634893
{"title":"IEEE Magnetics Society Information","authors":"","doi":"10.1109/TMAG.2025.3634893","DOIUrl":"https://doi.org/10.1109/TMAG.2025.3634893","url":null,"abstract":"","PeriodicalId":13405,"journal":{"name":"IEEE Transactions on Magnetics","volume":"61 12","pages":"C2-C2"},"PeriodicalIF":1.9,"publicationDate":"2025-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11269913","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145600710","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-25DOI: 10.1109/TMAG.2025.3636893
S. Clénet;J. Korecki;H. Igarashi;S. Yin;X. Kong
This article proposes a forward method to determine the optimal direction of the magnetization of permanent magnets, as well as their optimal shape, in order to maximize the magnetic flux in a coil. The method can be advantageously used, for example, during the design stage of an electrical machine in order to maximize the flux in the stator windings generated by the permanent magnets located on the rotor. The method is first developed in the continuous domain. It appears that the optimal permanent magnet configuration can be determined from the magnetic flux density distribution generated by the coil when it is supplied by a current of 1 A. No need to solve any inverse problem to find the optimal configuration since the procedure is explicit. It is shown that this method remains valid in the discrete domain when the finite element method is applied, and can take advantage of this method for topology optimization. Two configurations of permanent magnet magnetization are considered: either having a continuously variable direction or made with blocks in which the direction is constant as in a Halbach array. In the same way, for topology optimization, two cases are considered when the magnetization is fixed or considered as a variable to be optimized. A 3-D example is treated in order to illustrate the effectiveness of the method.
{"title":"A Forward Approach for Topology Optimization and Magnetization Direction Optimization of Permanent Magnets","authors":"S. Clénet;J. Korecki;H. Igarashi;S. Yin;X. Kong","doi":"10.1109/TMAG.2025.3636893","DOIUrl":"https://doi.org/10.1109/TMAG.2025.3636893","url":null,"abstract":"This article proposes a forward method to determine the optimal direction of the magnetization of permanent magnets, as well as their optimal shape, in order to maximize the magnetic flux in a coil. The method can be advantageously used, for example, during the design stage of an electrical machine in order to maximize the flux in the stator windings generated by the permanent magnets located on the rotor. The method is first developed in the continuous domain. It appears that the optimal permanent magnet configuration can be determined from the magnetic flux density distribution generated by the coil when it is supplied by a current of 1 A. No need to solve any inverse problem to find the optimal configuration since the procedure is explicit. It is shown that this method remains valid in the discrete domain when the finite element method is applied, and can take advantage of this method for topology optimization. Two configurations of permanent magnet magnetization are considered: either having a continuously variable direction or made with blocks in which the direction is constant as in a Halbach array. In the same way, for topology optimization, two cases are considered when the magnetization is fixed or considered as a variable to be optimized. A 3-D example is treated in order to illustrate the effectiveness of the method.","PeriodicalId":13405,"journal":{"name":"IEEE Transactions on Magnetics","volume":"62 1","pages":"1-11"},"PeriodicalIF":1.9,"publicationDate":"2025-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11268310","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145847766","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-25DOI: 10.1109/TMAG.2025.3637158
Jan Pytlík;Ondřej Životský;Jiří Luňáček
In the article, experimentally measured magnetization curves obtained on an amorphous Fe77.5Si7.5B15 ribbon at room and elevated temperatures are fit using the differential isotropic model of ferromagnetic hysteresis (DIMFH). The temperature dependence of the DIMFH model parameters is analyzed both in the ferromagnetic region and near the Curie temperature and is related to the size of magnetic clusters. The simple two-level model with Weiss approximation is used to fit the temperature dependence of saturation magnetization.
{"title":"Differential Isotropic Model of Ferromagnetic Hysteresis: Temperature Dependence of Saturation Magnetization and Cluster Magnetic Moment","authors":"Jan Pytlík;Ondřej Životský;Jiří Luňáček","doi":"10.1109/TMAG.2025.3637158","DOIUrl":"https://doi.org/10.1109/TMAG.2025.3637158","url":null,"abstract":"In the article, experimentally measured magnetization curves obtained on an amorphous Fe77.5Si7.5B15 ribbon at room and elevated temperatures are fit using the differential isotropic model of ferromagnetic hysteresis (DIMFH). The temperature dependence of the DIMFH model parameters is analyzed both in the ferromagnetic region and near the Curie temperature and is related to the size of magnetic clusters. The simple two-level model with Weiss approximation is used to fit the temperature dependence of saturation magnetization.","PeriodicalId":13405,"journal":{"name":"IEEE Transactions on Magnetics","volume":"62 1","pages":"1-4"},"PeriodicalIF":1.9,"publicationDate":"2025-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145847765","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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