Pub Date : 2026-08-01Epub Date: 2026-06-24DOI: 10.1109/TMAG.2026.3707031
Aleksey A. Girich;Sergey Yu. Polevoy;Sergey I. Tarapov
This article investigates intermode interactions in a planar microwave photon–magnon converter operating in the nonlinear regime. Numerical analysis is performed to compare the spectral characteristics of the planar converter with predictions of mechanical and electrodynamic coupled-oscillator models. A nonmonotonic dependence of the effective coupling strength on the input microwave power is revealed: the coupling increases with power up to a nonlinear threshold and subsequently decreases due to energy redistribution between interacting modes. The obtained results are relevant for the optimization and power-based tuning of photon–magnon devices, hybrid microwave systems, and magnonic components.
{"title":"Power-Dependent Nonlinear Coupling in a Planar Microwave Photon–Magnon Converter","authors":"Aleksey A. Girich;Sergey Yu. Polevoy;Sergey I. Tarapov","doi":"10.1109/TMAG.2026.3707031","DOIUrl":"https://doi.org/10.1109/TMAG.2026.3707031","url":null,"abstract":"This article investigates intermode interactions in a planar microwave photon–magnon converter operating in the nonlinear regime. Numerical analysis is performed to compare the spectral characteristics of the planar converter with predictions of mechanical and electrodynamic coupled-oscillator models. A nonmonotonic dependence of the effective coupling strength on the input microwave power is revealed: the coupling increases with power up to a nonlinear threshold and subsequently decreases due to energy redistribution between interacting modes. The obtained results are relevant for the optimization and power-based tuning of photon–magnon devices, hybrid microwave systems, and magnonic components.","PeriodicalId":13405,"journal":{"name":"IEEE Transactions on Magnetics","volume":"62 8","pages":"4000908-4000908"},"PeriodicalIF":1.9,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148627617","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 : 2026-08-01Epub Date: 2026-06-17DOI: 10.1109/TMAG.2026.3704383
Qilong Tang;Wei Duan;Zijun Zhu;Meilin Wan;Long You;Min Song
This article presents an in situ in-memory computing (IMC) architecture based on voltage-controlled magnetic anisotropy (VCMA)-based magnetoresistive random access memory (MRAM), specifically designed for efficient implementation of subtractors and dividers. The architecture leverages ultralow energy consumption and fast switching characteristics of VCMA-magnetic tunnel junctions (MTJs) to perform logic operations directly within the memory array through a voltage division mechanism. We develop a reconfigurable logic primitive design that enables multiple logic functions—such as not, nand, , and minority (MIN)—simply by adjusting bias voltages. Building upon these fundamental units, we construct multiplexers, subtractors, and exact/approximate dividers, compactly mapped into the memory array. Simulation results demonstrate that, for a 4 KB MRAM implemented in NCSU FreePDK45 45 nm CMOS process, the proposed architecture can achieve a peak throughput of 512 GOPS and a corresponding energy efficiency of 99.853 TOPS/W. The proposed 8 bit subtractor achieves 43.85% area reduction and 53.66% latency reduction compared to the state-of-the-art approach. The 16/8 bit divider occupies 288 cells, with a latency of 214 cycles, while the approximate divider achieves over 52.39% area reduction and 66.39% latency reduction, maintaining excellent performance in application-level tasks such as image background cancellation. This IMC architecture demonstrates significant potential for enabling resource-optimized operations in edge computing and embedded systems.
{"title":"VCMA-MRAM-Based In Situ, In-Memory Computing Architecture for Subtractors and Dividers","authors":"Qilong Tang;Wei Duan;Zijun Zhu;Meilin Wan;Long You;Min Song","doi":"10.1109/TMAG.2026.3704383","DOIUrl":"https://doi.org/10.1109/TMAG.2026.3704383","url":null,"abstract":"This article presents an in situ in-memory computing (IMC) architecture based on voltage-controlled magnetic anisotropy (VCMA)-based magnetoresistive random access memory (MRAM), specifically designed for efficient implementation of subtractors and dividers. The architecture leverages ultralow energy consumption and fast switching characteristics of VCMA-magnetic tunnel junctions (MTJs) to perform logic operations directly within the memory array through a voltage division mechanism. We develop a reconfigurable logic primitive design that enables multiple logic functions—such as <sc>not</small>, <sc>nand</small>, <sc>, and minority (MIN)—simply by adjusting bias voltages. Building upon these fundamental units, we construct multiplexers, subtractors, and exact/approximate dividers, compactly mapped into the memory array. Simulation results demonstrate that, for a 4 KB MRAM implemented in NCSU FreePDK45 45 nm CMOS process, the proposed architecture can achieve a peak throughput of 512 GOPS and a corresponding energy efficiency of 99.853 TOPS/W. The proposed 8 bit subtractor achieves 43.85% area reduction and 53.66% latency reduction compared to the state-of-the-art approach. The 16/8 bit divider occupies 288 cells, with a latency of 214 cycles, while the approximate divider achieves over 52.39% area reduction and 66.39% latency reduction, maintaining excellent performance in application-level tasks such as image background cancellation. This IMC architecture demonstrates significant potential for enabling resource-optimized operations in edge computing and embedded systems.","PeriodicalId":13405,"journal":{"name":"IEEE Transactions on Magnetics","volume":"62 8","pages":"3400610-3400610"},"PeriodicalIF":1.9,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148626094","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 : 2026-08-01Epub Date: 2026-06-17DOI: 10.1109/TMAG.2026.3704446
Zhengya Zhang;Bohuan Lin;Min Chen;Bingxin Huang;Anke Klingner;Wei Xue;Fengping Li;Wujun Geng;Sarthak Misra;Islam S. M. Khalil
Great care is required when employing two-dipole magnetic actuation systems to navigate untethered magnetic devices (UMDs) in in vivo medical applications, as uncontrolled gradient forces may lead to tissue trauma or damage. Therefore, it is critical to evaluate the full range of forces that may act on UMDs during operation. This article introduces a novel method for estimating the upper and lower bounds of the maximal magnetic gradient force acting on UMDs under the influence of two synchronized rotating magnetic dipoles. This study investigates the characteristics of the magnetic gradient force generated by a single rotating dipole and by two synchronized rotating dipoles. The results demonstrate that two synchronized dipoles are more likely to produce an approximately gradient-free region than a single dipole. Within this gradient-free region, the synchronized dipoles were robotically controlled to navigate a UMD inside an agar gel phantom. Closed-loop motion control experiments revealed that the maximum tracking error of a helical UMD actuated by two robotically controlled synchronized rotating dipoles was 3.89 mm.
{"title":"Characterizing the Magnetic Gradient Force of Untethered Magnetic Devices Using Two Synchronized Rotating Magnetic Dipoles","authors":"Zhengya Zhang;Bohuan Lin;Min Chen;Bingxin Huang;Anke Klingner;Wei Xue;Fengping Li;Wujun Geng;Sarthak Misra;Islam S. M. Khalil","doi":"10.1109/TMAG.2026.3704446","DOIUrl":"https://doi.org/10.1109/TMAG.2026.3704446","url":null,"abstract":"Great care is required when employing two-dipole magnetic actuation systems to navigate untethered magnetic devices (UMDs) in in vivo medical applications, as uncontrolled gradient forces may lead to tissue trauma or damage. Therefore, it is critical to evaluate the full range of forces that may act on UMDs during operation. This article introduces a novel method for estimating the upper and lower bounds of the maximal magnetic gradient force acting on UMDs under the influence of two synchronized rotating magnetic dipoles. This study investigates the characteristics of the magnetic gradient force generated by a single rotating dipole and by two synchronized rotating dipoles. The results demonstrate that two synchronized dipoles are more likely to produce an approximately gradient-free region than a single dipole. Within this gradient-free region, the synchronized dipoles were robotically controlled to navigate a UMD inside an agar gel phantom. Closed-loop motion control experiments revealed that the maximum tracking error of a helical UMD actuated by two robotically controlled synchronized rotating dipoles was 3.89 mm.","PeriodicalId":13405,"journal":{"name":"IEEE Transactions on Magnetics","volume":"62 8","pages":"4000810-4000810"},"PeriodicalIF":1.9,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148626781","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 : 2026-08-01Epub Date: 2026-06-22DOI: 10.1109/TMAG.2026.3705015
Kaio Sérgio Torres de Souz;Marcos Flávio de Campos;José Adilson de Castro
This work investigates the relationship among heat treatment, microstructural evolution, and magnetic properties in oriented hard ferrite magnets. The study combines directional magnetic characterization and grain-growth analysis after heat treatments performed at $1020~^{circ }$ C, $1060~^{circ }$ C, and $1100~^{circ }$ C for holding times between 0 and 10 h. Magnetic behavior was assessed from B(H) hysteresis loops measured along directions parallel (BP) and transverse (BT) to the orientation axis. From these measurements, remanence, coercivity, and loop squareness were analyzed as a function of crystallographic texture and microstructural evolution. Microstructural characterization was performed using optical microscopy and scanning electron microscopy (SEM), and the mean grain size was determined by image analysis. The results show that increasing thermal budget promotes grain growth and is associated with a reduction in coercivity, consistent with the decrease of effective microstructural barriers to magnetization reversal. As a methodological contribution, a comparative BP/BT loop-alignment procedure is proposed by imposing a common saturation reference and introducing an effective-field correction factor in the transverse direction. This procedure improves the interpretation of directional hysteresis data by separating geometric and effective-field effects from intrinsic magnetic hardness. In addition, this article discusses the applicability and limitations of the Stoner–Wohlfarth framework for real polycrystalline ferrites. Although the model captures the main qualitative trends, quantitative discrepancies remain because real materials exhibit intergranular interactions, local heterogeneities, and nonideal texture distributions. Overall, the results provide a consistent processing–structure–property interpretation for oriented hard ferrite magnets.
{"title":"Magnetic Characterization and Grain Growth in Oriented Hard Ferrite Magnets: Heat-Treatment Effects and Comparative BP/BT Hysteresis-Curve Alignment","authors":"Kaio Sérgio Torres de Souz;Marcos Flávio de Campos;José Adilson de Castro","doi":"10.1109/TMAG.2026.3705015","DOIUrl":"https://doi.org/10.1109/TMAG.2026.3705015","url":null,"abstract":"This work investigates the relationship among heat treatment, microstructural evolution, and magnetic properties in oriented hard ferrite magnets. The study combines directional magnetic characterization and grain-growth analysis after heat treatments performed at <inline-formula> <tex-math>$1020~^{circ }$ </tex-math></inline-formula>C, <inline-formula> <tex-math>$1060~^{circ }$ </tex-math></inline-formula>C, and <inline-formula> <tex-math>$1100~^{circ }$ </tex-math></inline-formula>C for holding times between 0 and 10 h. Magnetic behavior was assessed from B(H) hysteresis loops measured along directions parallel (BP) and transverse (BT) to the orientation axis. From these measurements, remanence, coercivity, and loop squareness were analyzed as a function of crystallographic texture and microstructural evolution. Microstructural characterization was performed using optical microscopy and scanning electron microscopy (SEM), and the mean grain size was determined by image analysis. The results show that increasing thermal budget promotes grain growth and is associated with a reduction in coercivity, consistent with the decrease of effective microstructural barriers to magnetization reversal. As a methodological contribution, a comparative BP/BT loop-alignment procedure is proposed by imposing a common saturation reference and introducing an effective-field correction factor in the transverse direction. This procedure improves the interpretation of directional hysteresis data by separating geometric and effective-field effects from intrinsic magnetic hardness. In addition, this article discusses the applicability and limitations of the Stoner–Wohlfarth framework for real polycrystalline ferrites. Although the model captures the main qualitative trends, quantitative discrepancies remain because real materials exhibit intergranular interactions, local heterogeneities, and nonideal texture distributions. Overall, the results provide a consistent processing–structure–property interpretation for oriented hard ferrite magnets.","PeriodicalId":13405,"journal":{"name":"IEEE Transactions on Magnetics","volume":"62 8","pages":"2100512-2100512"},"PeriodicalIF":1.9,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148627644","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 : 2026-08-01Epub Date: 2026-07-28DOI: 10.1109/TMAG.2026.3718220
{"title":"Imagine a community hopeful for the future","authors":"","doi":"10.1109/TMAG.2026.3718220","DOIUrl":"https://doi.org/10.1109/TMAG.2026.3718220","url":null,"abstract":"","PeriodicalId":13405,"journal":{"name":"IEEE Transactions on Magnetics","volume":"62 8","pages":"9801601-9801601"},"PeriodicalIF":1.9,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11627150","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148628227","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 : 2026-08-01Epub Date: 2026-06-26DOI: 10.1109/TMAG.2026.3707574
Miroslav Hennel;Ladislav Galdun;Samuel Nalevanko;Tomas Ryba;Michal Varga;Pavel Diko;Rastislav Varga
The present study investigates the new preparation approach for magnetocaloric Co–Ni–Ga-based Heusler alloys in the form of glass-coated microwires. The main aim was to improve the magnetic properties through the strong shape anisotropy, which is provided by the rapid solidification process of the Taylor–Ulitovsky method. While the structural analysis confirmed a disordered A2 Heusler phase at room temperature, the magnetic analyses revealed not only the highest saturation magnetization value among the known Co–Ni–Ga Heusler alloys with similar chemical composition but also the presence of a martensitic phase transformation at the temperature of about 185 K. Thus, the relatively sharp magnetic entropy change and the surface modification in the form of a glass cover predetermine the Co–Ni–Ga glass-coated compounds for future research in the framework of the micro-magnetocaloric coolers.
本文研究了以玻璃包覆微丝形式制备磁热co - ni - ga基Heusler合金的新方法。主要目的是通过泰勒-乌里托夫斯基快速凝固过程提供的强形状各向异性来改善磁性能。在室温下，结构分析证实其为无序的A2 Heusler相，而磁性分析表明，在化学成分相似的Co-Ni-Ga Heusler合金中，饱和磁化值最高，并且在185 K左右的温度下存在马氏体相变。因此，相对剧烈的磁熵变化和玻璃盖形式的表面修饰为未来微磁热冷却器框架下的Co-Ni-Ga玻璃涂层化合物的研究奠定了基础。
{"title":"Phase Transitions and Magnetocaloric Effect Study on Co2NiGa Glass-Coated Heusler Microwire","authors":"Miroslav Hennel;Ladislav Galdun;Samuel Nalevanko;Tomas Ryba;Michal Varga;Pavel Diko;Rastislav Varga","doi":"10.1109/TMAG.2026.3707574","DOIUrl":"https://doi.org/10.1109/TMAG.2026.3707574","url":null,"abstract":"The present study investigates the new preparation approach for magnetocaloric Co–Ni–Ga-based Heusler alloys in the form of glass-coated microwires. The main aim was to improve the magnetic properties through the strong shape anisotropy, which is provided by the rapid solidification process of the Taylor–Ulitovsky method. While the structural analysis confirmed a disordered <italic>A2</i> Heusler phase at room temperature, the magnetic analyses revealed not only the highest saturation magnetization value among the known Co–Ni–Ga Heusler alloys with similar chemical composition but also the presence of a martensitic phase transformation at the temperature of about 185 K. Thus, the relatively sharp magnetic entropy change and the surface modification in the form of a glass cover predetermine the Co–Ni–Ga glass-coated compounds for future research in the framework of the micro-magnetocaloric coolers.","PeriodicalId":13405,"journal":{"name":"IEEE Transactions on Magnetics","volume":"62 8","pages":"2500405-2500405"},"PeriodicalIF":1.9,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148627792","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 : 2026-08-01Epub Date: 2026-06-22DOI: 10.1109/TMAG.2026.3705391
Dan Yang;Tianyi Wu;Zhaoqun Wang;Chao Wu;Bin Xu
To address the complex optimization of gradient magnetic field in electromagnetic vascular imaging, this article proposes a dual-indicator dynamic-reinitialization particle swarm optimization (DIDR-PSO). The algorithm introduces a dual-indicator state evaluation, incorporating a stagnation factor and population aggregation degree to accurately detect when the swarm is trapped in local optima. Upon detection, a dynamic reinitialization operation is triggered to guide particles toward unvisited regions, effectively mitigating the premature convergence typical of standard PSO. A weighted composite fitness function is employed to collaboratively optimize gradient strength and field uniformity while adhering to physical constraints on coil volume and power consumption. Validation using CEC2017 benchmark functions demonstrates the superior search robustness and stability of the proposed method. When applied to a combined coil structure, the DIDR-PSO algorithm increased the average gradient strength from 0.85 to 1.18 T/m and reduced gradient non-uniformity from 15.73% to 10.33%. The simulation results indicate that these enhancements improved the reconstruction accuracy for vessel position and radius by 4.40% and 2.08%, respectively. The experimental measurements from a physical prototype show strong agreement with the optimized design, yielding a mean absolute error of only 0.68 mT along the $y$ -axis.
{"title":"Gradient Magnetic Field Optimization Using DIDR-PSO for Electromagnetic Vascular Imaging","authors":"Dan Yang;Tianyi Wu;Zhaoqun Wang;Chao Wu;Bin Xu","doi":"10.1109/TMAG.2026.3705391","DOIUrl":"https://doi.org/10.1109/TMAG.2026.3705391","url":null,"abstract":"To address the complex optimization of gradient magnetic field in electromagnetic vascular imaging, this article proposes a dual-indicator dynamic-reinitialization particle swarm optimization (DIDR-PSO). The algorithm introduces a dual-indicator state evaluation, incorporating a stagnation factor and population aggregation degree to accurately detect when the swarm is trapped in local optima. Upon detection, a dynamic reinitialization operation is triggered to guide particles toward unvisited regions, effectively mitigating the premature convergence typical of standard PSO. A weighted composite fitness function is employed to collaboratively optimize gradient strength and field uniformity while adhering to physical constraints on coil volume and power consumption. Validation using CEC2017 benchmark functions demonstrates the superior search robustness and stability of the proposed method. When applied to a combined coil structure, the DIDR-PSO algorithm increased the average gradient strength from 0.85 to 1.18 T/m and reduced gradient non-uniformity from 15.73% to 10.33%. The simulation results indicate that these enhancements improved the reconstruction accuracy for vessel position and radius by 4.40% and 2.08%, respectively. The experimental measurements from a physical prototype show strong agreement with the optimized design, yielding a mean absolute error of only 0.68 mT along the <inline-formula> <tex-math>$y$ </tex-math></inline-formula>-axis.","PeriodicalId":13405,"journal":{"name":"IEEE Transactions on Magnetics","volume":"62 8","pages":"5100312-5100312"},"PeriodicalIF":1.9,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148627646","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 : 2026-08-01Epub Date: 2026-06-18DOI: 10.1109/TMAG.2026.3705203
Olena S. Yakovenko;Ludmila Yu. Matzui;Ludmila L. Vovchenko;Larysa Kaykan;Dmytro O. Zaiats;Kateryna V. Dubyk;Yulia S. Perets;Julia Mazurenko
This work presents a comparative study of the dielectric properties of epoxy-based three-component composites incorporating nanocarbon fillers: multi-walled carbon nanotubes or graphite nanoplatelets (GNPs) and spinel ferrites (NiFe2O4, CuFe2O4, and CoFe2${mathrm{O}}_{4}$ ). Ferrite nanoparticles were synthesized via the sol-gel autocombustion method, and thermally expanded graphite (TEG) was used to obtain GNPs. The hybrid fillers were embedded into an epoxy matrix with a carbon content varying from 2 to 5 wt. % and a ferrite content fixed at 20 wt. %. Structural characterization of the ferrite powders by scanning electron microscopy revealed their near-spherical morphology and agglomeration tendencies. The complex dielectric permittivity ($varepsilon ^{prime }{}_{r}$ and $varepsilon ^{"}{}_{r}$ ) and loss tangent (tg $delta $ ) of the composites were measured in the 1–500 MHz frequency range. Results indicate that dielectric properties are strongly dependent on the type and concentration of hybrid filler. A significant increase in $varepsilon ^{prime }{}_{r}$ and $varepsilon ^{"}{}_{r}$ was observed for composites with 5 wt. % nanocarbon content, especially for nanocarbon/NiFe2O4 systems, where $varepsilon ^{"}{}_{r}$ reached up to 252–420 at 1 MHz. These findings highlight the potential of hybrid nanocarbon/ferrite fillers to enhance the dielectric response of polymer composites in the radio frequency range, with applications in electromagnetic interference (EMI) shielding and tunable dielectric devices.
本研究比较了含纳米碳填料的环氧基三组分复合材料的介电性能：多壁碳纳米管或石墨纳米片（GNPs）和尖晶石铁氧体（NiFe2O4， CuFe2O4和CoFe2 ${mathrm{O}}_{4}$）。采用溶胶-凝胶自燃烧法制备了铁氧体纳米颗粒，并用热膨胀石墨（TEG）制备了GNPs。混合填料嵌入到碳含量从2到5吨不等的环氧树脂基体中。 % and a ferrite content fixed at 20 wt. %. Structural characterization of the ferrite powders by scanning electron microscopy revealed their near-spherical morphology and agglomeration tendencies. The complex dielectric permittivity ( $varepsilon ^{prime }{}_{r}$ and $varepsilon ^{"}{}_{r}$ ) and loss tangent (tg $delta $ ) of the composites were measured in the 1–500 MHz frequency range. Results indicate that dielectric properties are strongly dependent on the type and concentration of hybrid filler. A significant increase in $varepsilon ^{prime }{}_{r}$ and $varepsilon ^{"}{}_{r}$ was observed for composites with 5 wt. % nanocarbon content, especially for nanocarbon/NiFe2O4 systems, where $varepsilon ^{"}{}_{r}$ reached up to 252–420 at 1 MHz. These findings highlight the potential of hybrid nanocarbon/ferrite fillers to enhance the dielectric response of polymer composites in the radio frequency range, with applications in electromagnetic interference (EMI) shielding and tunable dielectric devices.
{"title":"Electrophysical Properties of Magnetic Composites With Ferrites and Nanocarbon","authors":"Olena S. Yakovenko;Ludmila Yu. Matzui;Ludmila L. Vovchenko;Larysa Kaykan;Dmytro O. Zaiats;Kateryna V. Dubyk;Yulia S. Perets;Julia Mazurenko","doi":"10.1109/TMAG.2026.3705203","DOIUrl":"https://doi.org/10.1109/TMAG.2026.3705203","url":null,"abstract":"This work presents a comparative study of the dielectric properties of epoxy-based three-component composites incorporating nanocarbon fillers: multi-walled carbon nanotubes or graphite nanoplatelets (GNPs) and spinel ferrites (NiFe<sub>2</sub>O<sub>4</sub>, CuFe<sub>2</sub>O<sub>4</sub>, and CoFe<sub>2</sub><inline-formula> <tex-math>${mathrm{O}}_{4}$ </tex-math></inline-formula>). Ferrite nanoparticles were synthesized via the sol-gel autocombustion method, and thermally expanded graphite (TEG) was used to obtain GNPs. The hybrid fillers were embedded into an epoxy matrix with a carbon content varying from 2 to 5 wt. % and a ferrite content fixed at 20 wt. %. Structural characterization of the ferrite powders by scanning electron microscopy revealed their near-spherical morphology and agglomeration tendencies. The complex dielectric permittivity (<inline-formula> <tex-math>$varepsilon ^{prime }{}_{r}$ </tex-math></inline-formula> and <inline-formula> <tex-math>$varepsilon ^{\"}{}_{r}$ </tex-math></inline-formula>) and loss tangent (<italic>tg</i> <inline-formula> <tex-math>$delta $ </tex-math></inline-formula>) of the composites were measured in the 1–500 MHz frequency range. Results indicate that dielectric properties are strongly dependent on the type and concentration of hybrid filler. A significant increase in <inline-formula> <tex-math>$varepsilon ^{prime }{}_{r}$ </tex-math></inline-formula> and <inline-formula> <tex-math>$varepsilon ^{\"}{}_{r}$ </tex-math></inline-formula> was observed for composites with 5 wt. % nanocarbon content, especially for nanocarbon/NiFe<sub>2</sub>O<sub>4</sub> systems, where <inline-formula> <tex-math>$varepsilon ^{\"}{}_{r}$ </tex-math></inline-formula> reached up to 252–420 at 1 MHz. These findings highlight the potential of hybrid nanocarbon/ferrite fillers to enhance the dielectric response of polymer composites in the radio frequency range, with applications in electromagnetic interference (EMI) shielding and tunable dielectric devices.","PeriodicalId":13405,"journal":{"name":"IEEE Transactions on Magnetics","volume":"62 8","pages":"2800106-2800106"},"PeriodicalIF":1.9,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148627662","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}
In this research, the crystal structure and electron transport properties of [Ni80${mathrm {Fe}}_{20}(d)$ /HfO2(3)]10/S discontinuous multilayers were studied. As a preparation method, the sequential magnetron sputtering was chosen. It was demonstrated that the microstructure of the thin-film samples consists of ferromagnetic nanoparticles embedded within an amorphous HfO2 matrix. For [Ni80$mathrm{Fe}_{20}(d)$ /HfO2(3)]10/S discontinuous multilayers with an effective thickness of ferromagnetic layers $d = 1$ –3 nm, the mechanism of variable-range hopping conduction, in which electrons make thermally activated flips between localized states in the insulator matrix, is dominant. It has been established that size dependences of resistivity $rho (d)$ and temperature coefficient of resistance (TCR) $beta (d)$ are monotonous. The resistivity value decreases, and the TCR value increases with the growth of the effective thickness of Ni80Fe20 layers. It was demonstrated that the interval of effective thicknesses of Ni80Fe20 layers can be divided into three parts: $d le 3$ nm (with insulator regime of conductivity), $d gt 4$ nm (with metal regime of conductivity), and 3 nm $lt ~d le 4$ nm (with transition regime of conductivity).
{"title":"Non-Ohmic Behavior in [Ni80Fe20/HfO2]n Discontinuous Multilayers","authors":"Oleksandr Pylypenko;Iryna Pazukha;Andrii Lohvynov;Kostayntyn Tyschenko;Yurii Shkurdoda;Serhii Vorobiov;Vladimir Tkáč;Vladimir Komanický","doi":"10.1109/TMAG.2026.3707577","DOIUrl":"https://doi.org/10.1109/TMAG.2026.3707577","url":null,"abstract":"In this research, the crystal structure and electron transport properties of [Ni<sub>80</sub><inline-formula> <tex-math>${mathrm {Fe}}_{20}(d)$ </tex-math></inline-formula>/HfO<sub>2</sub>(3)]<sub>10</sub>/S discontinuous multilayers were studied. As a preparation method, the sequential magnetron sputtering was chosen. It was demonstrated that the microstructure of the thin-film samples consists of ferromagnetic nanoparticles embedded within an amorphous HfO<sub>2</sub> matrix. For [Ni<sub>80</sub><inline-formula> <tex-math>$mathrm{Fe}_{20}(d)$ </tex-math></inline-formula>/HfO<sub>2</sub>(3)]<sub>10</sub>/S discontinuous multilayers with an effective thickness of ferromagnetic layers <inline-formula> <tex-math>$d = 1$ </tex-math></inline-formula>–3 nm, the mechanism of variable-range hopping conduction, in which electrons make thermally activated flips between localized states in the insulator matrix, is dominant. It has been established that size dependences of resistivity <inline-formula> <tex-math>$rho (d)$ </tex-math></inline-formula> and temperature coefficient of resistance (TCR) <inline-formula> <tex-math>$beta (d)$ </tex-math></inline-formula> are monotonous. The resistivity value decreases, and the TCR value increases with the growth of the effective thickness of Ni<sub>80</sub>Fe<sub>20</sub> layers. It was demonstrated that the interval of effective thicknesses of Ni<sub>80</sub>Fe<sub>20</sub> layers can be divided into three parts: <inline-formula> <tex-math>$d le 3$ </tex-math></inline-formula> nm (with insulator regime of conductivity), <inline-formula> <tex-math>$d gt 4$ </tex-math></inline-formula> nm (with metal regime of conductivity), and 3 nm <inline-formula> <tex-math>$lt ~d le 4$ </tex-math></inline-formula> nm (with transition regime of conductivity).","PeriodicalId":13405,"journal":{"name":"IEEE Transactions on Magnetics","volume":"62 8","pages":"2001604-2001604"},"PeriodicalIF":1.9,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148628065","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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