IEEE Magnetics Letters最新文献

{"title":"A Physics-Based Circuit Model for Magnetic Tunnel Junctions","authors":"Steven Louis;Hannah Bradley;Artem Litvinenko;Vasyl Tyberkevych","doi":"10.1109/LMAG.2025.3577475","DOIUrl":"https://doi.org/10.1109/LMAG.2025.3577475","url":null,"abstract":"This work presents an equivalent circuit model for magnetic tunnel junctions (MTJs) that accurately reproduces their magnetization dynamics and electrical behavior within the macrospin approximation. The model is validated through direct numerical simulations of the Landau–Lifshitz–Gilbert–Slonczewski (LLGS) equation, encompassing ferromagnetic resonance, field- and spin-torque-induced switching and spin-torque-induced oscillations. Simulation results exhibit excellent agreement between the equivalent circuit model and the LLGS-based simulations, confirming the model accuracy and utility for efficient circuit-level analysis of MTJs. The capability of handling time-dependent magnetic fields and voltage-driven excitations renders the model applicable to diverse areas, including neuromorphic computing, microwave signal processing, and spintronic memory technologies. By providing a computationally efficient yet physically rigorous circuit representation, this work facilitates seamless integration of MTJs into complex electronic systems, thereby accelerating the advancement of novel spintronic circuit architectures.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"16 ","pages":"1-5"},"PeriodicalIF":1.1,"publicationDate":"2025-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144641078","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":"Method to Suppress Polar Kerr Signal in a Longitudinal Magneto-Optic Kerr Effect Measurement","authors":"Ryan W. Greening;Elyssa D. DeVisscher;Xin Fan","doi":"10.1109/LMAG.2025.3577473","DOIUrl":"https://doi.org/10.1109/LMAG.2025.3577473","url":null,"abstract":"The magneto-optical Kerr effect (MOKE) is a convenient technique to study the magnetization of thin films. However, both polar and longitudinal MOKE responses contribute to the total Kerr response in a typical longitudinal MOKE measurement. Here, we present a simple optical technique to suppress the polar MOKE response in the oblique angle incidence by exploiting differences between polar and longitudinal MOKE responses upon double reflection from the sample. By using a mirror to reflect the beam and by selectively using a quarter-wave plate, the polar or longitudinal MOKE signals can be suppressed and, therefore, studied separately using the same oblique experimental setup. To demonstrate the feasibility of this technique, we use an out-of-plane magnetized Pt/Co/Pt film and a Pt/Co/Cu/NiFe heterostructure with both in-plane and out-of-plane magnetization. We show that the polar MOKE of the CoPt film can be suppressed by a factor of 6 compared to a conventional MOKE measurement. By accounting for birefringence, we further reduce the polar MOKE response in a longitudinal MOKE measurement of the Pt/Co/Cu/NiFe film by over 160 times compared to a conventional oblique-angle MOKE measurement.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"16 ","pages":"1-5"},"PeriodicalIF":1.1,"publicationDate":"2025-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144597698","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":"Effects of Ta Buffer Layer on Structural and Magnetic Properties of Sputtered Ni2FeAl","authors":"Aarzoo Dhull;Prashant Kumar;Vipul Sharma;Pawan S. Rana;Bijoy K. Kuanr","doi":"10.1109/LMAG.2025.3564795","DOIUrl":"https://doi.org/10.1109/LMAG.2025.3564795","url":null,"abstract":"In the present investigation, we report the growth of off-stoichiometric Ni-based Heusler thin films of different thicknesses (6–30 nm) on a Si (100) substrate by radio frequency sputtering at 300 °C. We have used an indigenously prepared target comprising thin sheets of Ni, Fe, and Al in specific proportions. Of all the Heusler alloys, Ni₂FeAl is the least researched alloy that may offer immense possibilities in developing spin-based devices. The Ni₅₅Fe₁₄Al₃₁ films crystallize into the A2 phase as confirmed by the diffraction pattern. With the increase in the thickness of films, surface roughness improves followed by an increase in saturation magnetization (<italic>M</i>_S). Further, we have explored the effect of Ta buffer on the static and dynamic magnetic behavior of films and compared it with unbuffered films. The Ta buffer layer significantly impacts the surface morphology of the films. The in-plane magnetic hysteresis loops indicate higher <italic>M</i>_S with Ta buffer. Dynamic magnetization is probed via ferromagnetic resonance technique over a broad band of microwave frequencies and has been quantified in terms of Gilbert damping constant (α). The Ta buffer reduces the Gilbert damping constant from 10.1 × 10⁻³ to 8.4 × 10⁻³ in 30 nm thick films.","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":"144314835","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":"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}