IEEE Magnetics Letters最新文献

{"title":"Detection of In-Plane Magnetized Grains With a Magnetoresistive Head","authors":"Yifei Chen;R. H. Victora","doi":"10.1109/LMAG.2025.3564876","DOIUrl":"https://doi.org/10.1109/LMAG.2025.3564876","url":null,"abstract":"Magnesium oxide (MgO) is an important component in heat-assisted magnetic recording (HAMR) media, serving as an excellent seed layer for perpendicular orientation of FePt grains. However, it is difficult to detect the in-plane magnetic grains caused by the MgO boundaries. This work uses micromagnetic simulation to study the detection of longitudinally magnetized grains in FePt-based HAMR media using a novel 45° magnetoresistive read head design. By leveraging the reduced in-plane anisotropy of FePt grains and the magnetostatic field generated by adjacent tracks, an asymmetric magnetization distribution is induced along the cross-track direction. This asymmetry facilitates the detection of in-plane magnetization components using playback signals obtained from micromagnetic simulations. The method effectively identifies noise sources, thus providing a cost-efficient alternative to other experimental techniques.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"16 ","pages":"1-4"},"PeriodicalIF":1.1,"publicationDate":"2025-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144177414","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"High-Permeability Magnetic Composites With Cement, Asphalt, and Epoxy Binders for Enhanced Performance Across Diverse Applications","authors":"Ibrahim Ellithy;Mauricio Esguerra;Rewanth Radhakrishnan","doi":"10.1109/LMAG.2025.3564881","DOIUrl":"https://doi.org/10.1109/LMAG.2025.3564881","url":null,"abstract":"As the global demand for energy transition and transport decarbonization intensifies, the development of advanced magnetizable materials becomes crucial for supporting large-scale applications. This study presents the optimization of MAGMENT composites, which are produced using recycled ferrite aggregates combined with binders, such as cement, asphalt, or epoxy. These composites are engineered to achieve high magnetic permeability and low core losses, key characteristics for efficient energy systems. Our results demonstrate that by fine-tuning the aggregate size and volume fraction, permeability can be significantly enhanced, with volume fractions above 65% showing the most promise. Although cement workability imposes a 73% limit, the performance of these composites still surpasses industry benchmarks, notably the KH-HT 60µ from KEDA, by refining the particle size distribution. Adjusting the nominal maximum aggregate size from 4.5 to 19 mm changes permeability from 40 to 180. The superior magnetic performance of the MC60 grade, particularly its minimal core losses, underscores its potential as a leading material in the market. These advancements are for applications in wireless charging, both static and dynamic, and in high-power transmission systems, addressing critical needs in sustainable transport and energy infrastructure. The use of recycled materials further aligns with the global push for environmentally responsible technologies.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"16 ","pages":"1-5"},"PeriodicalIF":1.1,"publicationDate":"2025-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144243821","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Temperature Dependence of Magnetization Reversal and Harmonic Spectrum in Low Curie Temperature Amorphous Microwires","authors":"Adrian Acuna;Larissa Panina;Nikolay Yudanov","doi":"10.1109/LMAG.2025.3564147","DOIUrl":"https://doi.org/10.1109/LMAG.2025.3564147","url":null,"abstract":"The present study focuses on the investigation of the magnetization reversal process in amorphous microwires of the composition Co_64.82Fe_3.9B_10.2Si₁₂Cr₉Mo_0.08, which possesses a low Curie temperature <inline-formula><tex-math>${{T}_c}$</tex-math></inline-formula> of 61 °<inline-formula><tex-math>$mathrm{C}$</tex-math></inline-formula>. The microwire retains a nearly rectangular hysteresis loop, an axial anisotropy, and a positive magnetostriction up to <inline-formula><tex-math>${{T}_c}$</tex-math></inline-formula>. The coercivity decreases with temperature, following the decrease in the saturation magnetization <inline-formula><tex-math>${{M}_s}$</tex-math></inline-formula>, but it has a different dependence on <inline-formula><tex-math>${{M}_s}$</tex-math></inline-formula> far from and near <inline-formula><tex-math>$ {{T}_c}$</tex-math></inline-formula>, which suggests different mechanisms of magnetostriction in these temperature intervals. Furthermore, the harmonic spectrum of the voltage induced during remagnetization is also temperature sensitive. The area under the voltage pulse is directly proportional to <inline-formula><tex-math>${{M}_s}$</tex-math></inline-formula>, resulting in a comparable dependence of the harmonic amplitudes. In the context of potential applications in wireless temperature sensors, measuring the harmonic spectrum offers distinct advantages based on lock-in techniques. In addition, the temperature range over which the harmonic spectrum varies most is extended by using two (or potentially few) microwires with different <inline-formula><tex-math>${{T}_c}$</tex-math></inline-formula>. The change in <inline-formula><tex-math>${{T}_c}$</tex-math></inline-formula> from 61 °<inline-formula><tex-math>$mathrm{C}$</tex-math></inline-formula> to 57 °<inline-formula><tex-math>$mathrm{C}$</tex-math></inline-formula> is achieved by current annealing of the same microwire, which helps to extend the temperature-sensitive range of the two microwire harmonic responses between 40 °<inline-formula><tex-math>$mathrm{C}$</tex-math></inline-formula> and 61 °<inline-formula><tex-math>$mathrm{C}$</tex-math></inline-formula>.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"16 ","pages":"1-5"},"PeriodicalIF":1.1,"publicationDate":"2025-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144123348","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Study of Structural and Magnetic Properties of Antiferromagnetic Cr2MnGe Heusler Alloy","authors":"Karthik G;Shipra Das;T. R. Naveen Kumar;K Ravichandran","doi":"10.1109/LMAG.2025.3560867","DOIUrl":"https://doi.org/10.1109/LMAG.2025.3560867","url":null,"abstract":"Engineered Heusler alloys have potential applications in spintronic devices owing to their fascinating properties. Therefore, we synthesized a ternary Cr₂MnGe Heusler alloy using a simple solid-state reaction. Rietveld refinement of the X-ray diffraction data confirmed the presence of a cubic Fd-3m structure, specifically the B32a disorder Heusler phase with a space group number of 227. The microstructure and chemical composition of the Cr₂MnGe sample confirmed agglomeration and adherence to the nominal composition of the Heusler alloy. Furthermore, the Cr₂MnGe sample exhibits antiferromagnetic behavior with ferromagnetic clusters due to the site swapping of Cr–Mn and Cr–Ge, which contributes to a magnetic signal in the zero-field-cooled and field-cooled measurements. These findings highlight the potential of Cr₂MnGe for application in magnetic tunnel junctions and spin valves, contributing to advancements in spintronic technologies.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"16 ","pages":"1-4"},"PeriodicalIF":1.1,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144232180","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Features and Peculiarities of Gate-Voltage Modulation of Spin-Orbit Interaction in FeB Nanomagnets: Insights Into the Physical Origins of the Voltage-Controlled Magnetic Anisotropy Effect","authors":"Vadym Zayets","doi":"10.1109/LMAG.2025.3560858","DOIUrl":"https://doi.org/10.1109/LMAG.2025.3560858","url":null,"abstract":"This letter systematically investigates the fundamental mechanisms driving the voltage-controlled magnetic anisotropy (VCMA) effect, with a focus on the dependencies of the anisotropy field and the strength of spin-orbit (SO) interaction on gate voltage, measured in Ta/FeB/MgO nanomagnets. Our findings reveal an intriguing opposite polarity in the gate-voltage dependencies of the anisotropy field and the coefficient of SO interaction across all studied nanomagnets. This discovery challenges the prevailing assumption that SO interaction is the primary contributor to the VCMA effect, instead suggesting that gate-voltage modulation of magnetization is likely the dominant factor, as its polarity aligns with the observed modulation of anisotropy. The modulation of magnetic anisotropy is governed by two major contributions with opposite polarities, which tend to counterbalance each other, reducing the overall VCMA effect. Optimizing this balance could significantly enhance the VCMA effect, offering a promising avenue for broadening its applications. In addition, our measurements confirm that gate voltage does not modulate the in-plane component of spin accumulation, providing further insights into the underlying mechanisms of the VCMA effect.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"16 ","pages":"1-4"},"PeriodicalIF":1.1,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144108338","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Size Dependence of the Read Voltage and Electrical Diameter of STT MRAM Cells","authors":"Goran Mihajlović;Wonjoon Jung;Noraica Dávila;Jeffrey Lille;Michael Tran;Jordan A. Katine;Michael K. Grobis","doi":"10.1109/LMAG.2025.3560889","DOIUrl":"https://doi.org/10.1109/LMAG.2025.3560889","url":null,"abstract":"We present an experimental study of the size-dependent tunneling magnetoresistance ratio (TMR) and voltage read signal in perpendicular spin transfer torque magnetoresistive random-access (MRAM) memory cells, which shows that the maximum read signal is mostly independent of the size, while TMR decreases with decreasing size. Our analysis shows that this is due to a size-dependent parasitic resistance specific to the nanofabrication process and that the intrinsic <inline-formula><tex-math>$Delta text{RA}$</tex-math></inline-formula> of the cells is size-independent. As a consequence, we show that the electrical diameter of an MRAM cell can be reliably extracted down to sub-20 nm assuming that <inline-formula><tex-math>$Delta text{RA}$</tex-math></inline-formula> does not depend on the cell size.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"16 ","pages":"1-5"},"PeriodicalIF":1.1,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144072775","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fast Acquisition of Sensor Array Geometry of Whole-Head Magnetoencephalograph Systems Using a Neural Network","authors":"Yoshiaki Adachi;Daisuke Oyama;Gen Uehara","doi":"10.1109/LMAG.2025.3560886","DOIUrl":"https://doi.org/10.1109/LMAG.2025.3560886","url":null,"abstract":"Acquiring position, orientation, and sensitivity of magnetometers in a helmet-shaped sensor array is crucial for accurate current source reconstruction in magnetoencephalography. To determine these parameters for each magnetometer, we utilize a spherical calibration coil array. In our previous study, the position and orientation of each magnetometer were determined as the solution of an inverse problem through a numerical search that minimized the difference between the theoretical magnetic field signals from each coil and the measured signals detected by the magnetometer. In this study, we applied a deep neural network to estimate the position and orientation of each magnetometer in the helmet-shaped sensor array without solving the inverse problem. A total of 223 million pairs of a given magnetometer's five parameters (<italic>x</i>, <italic>y</i>, <italic>z</i>, <italic>θ</i>, and <italic>ϕ</i>) and the corresponding theoretical magnetic field signals from the coils were used to train the neural network. The training process required approximately 53 h using a commercially available GPU-equipped computer. The trained neural network was then applied to acquire the sensor geometry from magnetic field data obtained during a conventional calibration procedure for a 160-channel whole-head magnetoencephalograph system using a spherical calibration coil array. The position and orientation of each magnetometer estimated by this method deviated by an average of 0.65 mm and 0.51°, respectively, from those obtained via the conventional inverse problem approach. The acquisition of the geometry for all 160 magnetometers required less than 8 ms. With such high-speed acquisition, this approach opens possibilities for future applications in acquiring positional information of wearable sensor arrays whose structures change in real time.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"16 ","pages":"1-5"},"PeriodicalIF":1.1,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10964712","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144179108","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Voltage-Modulated Magneto-Dynamics in Spin Hall Nano-Oscillators","authors":"Linrong Yao;Hongchao Xie;Bin Hu;Sheng Jiang","doi":"10.1109/LMAG.2025.3555942","DOIUrl":"https://doi.org/10.1109/LMAG.2025.3555942","url":null,"abstract":"Spin Hall nano-oscillators (SHNOs) have garnered attention due to their broad application prospects in microwave generators, information storage, and artificial intelligence computing. This has necessitated the development of efficient methods to control the magneto-dynamics of SHNOs. Magnetic field control requires a field generator, and current control suffers from a narrow frequency range and low efficiency. We present an approach to efficiently control the SHNO magneto-dynamics, i.e., a piezoelectric-based SHNO system, to achieve voltage-modulated magneto-dynamics through magneto-electric coupling. Through micromagnetic simulations, this work demonstrates the indirect control of the magneto-dynamics by voltage-modulated magnetic anisotropy, revealing the impact of changes in magnetic anisotropy on the magneto-dynamics and the underlying physical mechanisms. This discovery enhances the degree of freedom for electrical modulation of SHNOs and contributes to developing advanced spintronic devices.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"16 ","pages":"1-5"},"PeriodicalIF":1.1,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143908431","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"YIG/CoFeB Bilayer Magnonic Isolator","authors":"Noura Zenbaa;Khrystyna O. Levchenko;Jaganandha Panda;Kristýna Davídková;Moritz Ruhwedel;Sebastian Knauer;Morris Lindner;Carsten Dubs;Qi Wang;Michal Urbánek;Philipp Pirro;Andrii V. Chumak","doi":"10.1109/LMAG.2025.3551990","DOIUrl":"https://doi.org/10.1109/LMAG.2025.3551990","url":null,"abstract":"We demonstrate a magnonic isolator based on a bilayer structure of yttrium iron garnet (YIG) and cobalt iron boron (CoFeB). The bilayer exhibits pronounced nonreciprocal spin-wave propagation, enabled by dipolar coupling and the magnetic properties of the two layers. The YIG layer provides low damping and efficient spin-wave propagation, whereas the CoFeB layer introduces strong magnetic anisotropy, critical for achieving the isolator functionality. Experimental results, supported by numerical simulations, show unidirectional propagation of magneto-static surface spin waves, significantly suppressing backscattered waves. This behavior was confirmed through wavevector-resolved and microfocused Brillouin light scattering measurements and is supported by numerical simulations. The developed YIG/SiO<inline-formula><tex-math>$_{2}$</tex-math></inline-formula>/CoFeB bilayer magnonic isolator demonstrates the feasibility of leveraging nonreciprocal spin-wave dynamics for functional magnonic devices, paving the way for energy-efficient, wave-based signal processing technologies.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"16 ","pages":"1-5"},"PeriodicalIF":1.1,"publicationDate":"2025-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10930529","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143865306","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ready-to-Use Composite Fused Deposition Modeling Filaments Produced With Polylactic Acid and Recycled Nd–Fe–B Nanocrystalline Powder for Additive Manufacturing of Bonded Magnets","authors":"Gabriel M. Vieira;Marcelo A. Rosa;Paulo A. P. Wendhausen;Maximiliano D. Martins","doi":"10.1109/LMAG.2025.3551243","DOIUrl":"https://doi.org/10.1109/LMAG.2025.3551243","url":null,"abstract":"Fused deposition modeling (FDM) is an additive manufacturing technique that has become widely used in many fields of engineering and has recently proven to be suitable for producing complex, net-shaped bonded Nd–Fe–B magnets. At the same time, recycling end-of-life magnets has been an emerging concern due to their increasing presence in current technologies and the intrinsic scarcity of rare-Earth elements, such as neodymium and praseodymium. Here, we investigated the feasibility of using recycled nanocrystalline Nd–Fe–B powders, obtained from a hydrogenation–disproportionation–desorption–recombination (HDDR) process in the preparation of FDM feedstock and subsequent printing of magnetic parts. Recycled magnetic powder was mixed with polylactic acid and extruded into filaments containing increasing volume fractions of magnetic powder. It was possible to obtain filaments containing from 6.7% to 23.6% in volume (30.4 to 65.2 wt.%) of the magnetic powder, from which parts could be printed, reaching maximum coercivity (<italic>H</i>_cj) of 707.7 ± 3.5 kA/m, maximum remanence (<italic>B</i>_r) of 84.5 ± 0.4 mT, maximum energy product (<italic>BH</i>_max) of 1.3 kJ/m³, and average part porosity of 42 ± 8%. Coercivity loss of about 8.6% was observed in the printed parts compared to the recycled powder (750±75 kA/m). Aging experiments showed that such loss may be a combined effect of thermal and oxidation effects of the magnetic particles during the additive manufacturing processing. The present work has demonstrated the achievement of ready-to-use, high-coercivity FDM filaments, and 3-D-printed parts using recycled Nd–Fe–B HDDR powders.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"16 ","pages":"1-5"},"PeriodicalIF":1.1,"publicationDate":"2025-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143856196","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}