{"title":"Novel Transcranial Magnetic Stimulation Coil for Precise Deep Brain Location Stimulation","authors":"Zihan Tang;Tao Zhang;Shuang Zhang","doi":"10.1109/LMAG.2026.3663877","DOIUrl":"https://doi.org/10.1109/LMAG.2026.3663877","url":null,"abstract":"This letter presents an eccentric inverted-cone three-dimensional transcranial magnetic stimulation (TMS) coil to address the poor focusing ability and small effective stimulation depth in commercial TMS coils. The performance of the coil is compared with that of several commercial and theoretical coils via finite element modeling. Spherical head model simulations reveal that the coil outperforms existing coils in terms of focusing ability and effective stimulation depth. Furthermore, employing a dual-coil combination effectively enhances the maximum induced electric field strength and increases the focusing ability and effective stimulation depth of the signal.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"17 ","pages":"1-5"},"PeriodicalIF":1.1,"publicationDate":"2026-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147440675","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 on Worst-Case Gradient Forces on Untethered Magnetic Devices Using Two Synchronized Rotating Magnetic Dipoles","authors":"Zhengya Zhang;Bohuan Lin;Anke Klingner;Guang Feng;Yanfei Liao;Jian Guo;Wei Xue;Fengping Li;Wujun Geng;Sarthak Misra;Islam S.M.Khalil","doi":"10.1109/LMAG.2026.3657287","DOIUrl":"https://doi.org/10.1109/LMAG.2026.3657287","url":null,"abstract":"Untethered magnetic devices (UMDs) hold significant clinical potential for removing blood clots. However, in the complex intravascular environment, their locomotion may be disturbed. Such disturbances can lead to variations in the magnetic gradient force exerted on the UMD, increasing the risk of vascular damage. Therefore, evaluating the magnetic gradient force acting on the UMD under worst-case conditions is essential for risk mitigation. In this letter, we a novel method to estimate the upper and lower bounds of the worst-case magnetic gradient force acting on the UMD, with actuation provided by two synchronized rotating magnetic dipoles. To assess the robustness of the algorithm, we conducted a Monte Carlo simulation in which the dipole directions of the two synchronized rotating magnetic dipoles and the dipole direction of the UMD were randomly varied 1 000 000 times in the three-dimensional space to simulate all possible scenarios that may be encountered by the UMD in intravascular environments. The simulation results indicate that the worst-case magnetic gradient force remains below the upper bound predicted by the algorithm, thereby validating its effectiveness.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"17 ","pages":"1-5"},"PeriodicalIF":1.1,"publicationDate":"2026-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146223702","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}
Kristen Booth;Aqarib Hussain;Jacob L. Jones;Todd C. Monson
{"title":"Self-Cooling Multiferroic Magnetic Devices","authors":"Kristen Booth;Aqarib Hussain;Jacob L. Jones;Todd C. Monson","doi":"10.1109/LMAG.2026.3657139","DOIUrl":"https://doi.org/10.1109/LMAG.2026.3657139","url":null,"abstract":"Increasing switching frequency reduces magnetic volume, but conventional ferrites, used from tens to hundreds of kilohertz, cannot sustain the temperature and frequency ranges demanded by current and emerging wide bandgap and ultrawide bandgap devices. This work presents a novel magnetic material architecture combining nanocrystalline magnetic material and multiferroic layers for megahertz power conversion. The high saturation flux density of nanocrystalline alloys supports miniaturization but is traditionally constrained by excessive losses above 10 kHz. A revolutionary multiferroic material with solid-state cooling via caloric materials is defined that will enable the next generation of magnetic devices for wide-bandgap-integrated designs. This letter highlights the fundamental physics behind this capability alongside early development of a finite element analysis for the multiferroic-based magnetic device using ANSYS, showing that the core achieves more uniform thermal distribution and reduces peak temperature by 9 <inline-formula><tex-math>$^{circ }$</tex-math></inline-formula>C compared to conventional ferrites.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"17 ","pages":"1-4"},"PeriodicalIF":1.1,"publicationDate":"2026-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147299719","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}
Kaiyuan Zhou;Wenlong Yang;Xuejie Xie;Hengan Zhou;Cheng Zhuo;Enlong Liu
{"title":"Asymmetric Write Error Rate Caused by Self-Heating-Induced Offset Field Shift in Spin-Orbit-Torque Magnetic Tunnel Junctions","authors":"Kaiyuan Zhou;Wenlong Yang;Xuejie Xie;Hengan Zhou;Cheng Zhuo;Enlong Liu","doi":"10.1109/LMAG.2026.3652528","DOIUrl":"https://doi.org/10.1109/LMAG.2026.3652528","url":null,"abstract":"In this letter, we study the asymmetric increase of write error rate (WER) as the write voltage is elevated in spin-orbit-torque (SOT) magnetic tunnel junctions (MTJs) with perpendicular magnetic anisotropy. Besides the decrease of the free layer’s (FL) coercive field rendering the FL more vulnerable to the influence of offset field from synthetic antiferromagnets (SAFs), we observe, that during the write process, the temperature rise caused by the self-heating effect also modifies the magnetic properties of SAF layers in MTJ stacks. Through the measurement and analysis of two device types with different SAF designs, the amplitude and direction of the offset field show different temperature dependence, which determines an opposite preferentially stable state for the FL, and hence the anomalously high WER. Macrospin simulations of WER incorporating self-heating effect and temperature-dependent magnetic properties in both FL and SAF reproduce well the experimental observations. These findings offer novel insights into the role of the offset field and its temperature dependence in optimizing WER performance in SOT-MTJ devices.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"17 ","pages":"1-5"},"PeriodicalIF":1.1,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146139120","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}
K. Koike;T. Okawa;Y. Ikagawa;T. Amiya;G. Tahara;M. Itakura;T. Yasunaga;M. Nakano
{"title":"Magnetic Properties of Nd-Fe-B Single Dots Fabricated Using the PLD–LIFT Method","authors":"K. Koike;T. Okawa;Y. Ikagawa;T. Amiya;G. Tahara;M. Itakura;T. Yasunaga;M. Nakano","doi":"10.1109/LMAG.2026.3652505","DOIUrl":"https://doi.org/10.1109/LMAG.2026.3652505","url":null,"abstract":"Single-dot Nd-Fe-B micromagnets were fabricated using the pulsed laser deposition-laser-induced forward transfer (PLD–LIFT) technique, and their magnetic properties were systematically examined. Hysteresis measurements with a vibrating sample magneto meter revealed that the coercivity (<italic>H</i><sub>c</sub>) was nearly independent of laser power, whereas an increased defocus rate (DF rate) enhanced <italic>H</i><sub>c</sub> up to 340 kA/m. Scanning electron microscopy and cross-sectional scanning transmission electron microscopy analyses revealed that each dot comprises grains ranging from submicrometer to micrometer scale. Within these grains, an Nd<sub>2</sub>Fe<sub>14</sub>B core is encapsulated by an Fe-rich matrix containing dispersed Nd oxides. The thickness of this Fe-rich outer shell modifies the exchange pathway at the Nd<sub>2</sub>Fe<sub>14</sub>B/Fe interface, giving rise to the characteristic two-step demagnetization. Guided by these observations, a simplified Nd<sub>2</sub>Fe<sub>14</sub>B/α-Fe core–shell model was developed and evaluated through micromagnetic simulations, which successfully reproduced the stepwise reversal and clarified DF’s role in suppressing soft-phase connectivity and improving loop squareness. Collectively, these findings identify DF rate as the dominant processing parameter and provide practical guidelines for tailoring PLD–LIFT Nd-Fe-B micromagnets toward microelectromechanical systems applications.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"17 ","pages":"1-5"},"PeriodicalIF":1.1,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146223734","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":"Developing Laser-Assisted Heating Magnetization Utilizing a Distributed External Magnetic Field for Magnetic MEMS","authors":"Keita Nagai;Tadahiko Shinshi","doi":"10.1109/LMAG.2026.3652483","DOIUrl":"https://doi.org/10.1109/LMAG.2026.3652483","url":null,"abstract":"Self-demagnetizing fields in uniformly magnetized flat magnets limit the surface magnetic flux density and output power of magnetic microelectromechanical systems (MEMSs). In laser-assisted heating magnetization (LAHM), the laser locally reduces the coercivity, and a uniform reverse magnetic field subsequently reverses the magnetization. LAHM was developed to produce fine multipole patterns and address these performance limitations. This study extends LAHM by superimposing a distributed external magnetic field tailored to the target pattern. The field is generated by a prepatterned multipole master NdFeB magnet (<inline-formula><tex-math>$B_{r}$</tex-math></inline-formula> = 1.30 T and <inline-formula><tex-math>$H_{cj}$</tex-math></inline-formula> = 2388 kA/m) placed on a uniform reverse-field source, which strengthens the local magnetizing field in the target areas and attenuates it elsewhere. Experiments employing 0.3 mm thick NdFeB samples demonstrate that distributed-field LAHM increases the magnetization ratio by 10.8% and the peak-to-peak surface magnetic flux density by 54.2 mT compared with conventional uniform-field LAHM. These results indicate a potential route to higher performance multipole magnets for MEMS applications.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"17 ","pages":"1-5"},"PeriodicalIF":1.1,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146175752","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}
IEEE Magnetics LettersPub Date : 2026-01-01Epub Date: 2026-03-17DOI: 10.1109/LMAG.2026.3674363
Travis J. Allen;Levi M. Barker;Jake J. Abbott
{"title":"Assume a Spherical Cube: Bounding the Force and Torque Induced on a Conductive Nonmagnetic Cube by a Rotating Magnetic Dipole","authors":"Travis J. Allen;Levi M. Barker;Jake J. Abbott","doi":"10.1109/LMAG.2026.3674363","DOIUrl":"https://doi.org/10.1109/LMAG.2026.3674363","url":null,"abstract":"A time-varying magnetic field induces electric currents in a conductive object, which in turn induces a force–torque wrench on the object that is not due to ferromagnetism. Prior work empirically modeled the wrench induced in a solid sphere by a rotating magnetic dipole (RMD) field, and then used this model to perform contactless manipulation using multiple RMD field sources, motivated by application in on-orbit satellite servicing and space-debris capture. In this letter, we measure the induced wrench on a conductive, nonferromagnetic cube—which, unlike on a sphere, is not invariant to orientation—in six canonical configurations, and we compare it to that of a sphere with identical volume. Results show that such a spherical model provides a reasonable orientation-invariant approximation of a cube. Further, the induced wrench can be bounded by considering the induced wrenches on spheres with <inline-formula><tex-math>$pm 15%$</tex-math></inline-formula> volume.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"17 ","pages":"1-5"},"PeriodicalIF":1.1,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147696637","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}
IEEE Magnetics LettersPub Date : 2026-01-01Epub Date: 2026-02-11DOI: 10.1109/LMAG.2026.3663904
Dimitrios Niarchos;Margarit Gjoka;Vassilis Psycharis;Alexandra Ioannidou;Eamonn Devlin;Athanasios Sigalos;Dimitrios I. Anyfantis
{"title":"Toward Realization of Bulk L10-FeNi","authors":"Dimitrios Niarchos;Margarit Gjoka;Vassilis Psycharis;Alexandra Ioannidou;Eamonn Devlin;Athanasios Sigalos;Dimitrios I. Anyfantis","doi":"10.1109/LMAG.2026.3663904","DOIUrl":"https://doi.org/10.1109/LMAG.2026.3663904","url":null,"abstract":"In this letter, we demonstrate for the first time the preparation of bulk L1<sub>0</sub>-FeNi embedded in an fcc FeNi by alloying Fe and Ni during casting with 5%–10% indium metal and annealing at 350 °C for a week. From X-ray diffraction, magnetization, and Mössbauer data, we have strong indications that the L1<sub>0</sub>-FeNi phase is formed and coexists with the cubic A1-FeNi at a ratio of 30/70 for the sample with 5% In and 20/80% for the sample with 10% In, as derived from X-ray diffraction. This finding is supported by the Mössbauer data, where the ratio of L1<sub>0</sub>-FeNi to A1-FeNi is 48/52 and 24/76, respectively. The morphology of the alloys is sponge-like and very brittle, and the final In stoichiometry is much less than the nominal one.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"17 ","pages":"1-5"},"PeriodicalIF":1.1,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11393511","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147557790","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}
IEEE Magnetics LettersPub Date : 2026-01-01Epub Date: 2026-03-16DOI: 10.1109/LMAG.2026.3674354
Ceziana Pereira da Costa;Ana Lucia Dantas;Artur da Silva Carriço
{"title":"Tuning the Remanent Magnetic State in Square Ferromagnetic Nanorings","authors":"Ceziana Pereira da Costa;Ana Lucia Dantas;Artur da Silva Carriço","doi":"10.1109/LMAG.2026.3674354","DOIUrl":"https://doi.org/10.1109/LMAG.2026.3674354","url":null,"abstract":"We present a micromagnetic study of remanent magnetic states in square Fe and Permalloy nanorings, emphasizing the roles of field history and geometric confinement. Remanent configurations are obtained by saturating the rings under different field orientations and reducing the field to zero. The results reveal strong path dependence: diagonal and perpendicular saturation stabilize onion-like and vortex states, respectively, whereas edge-field saturation induces transitions among buckle-like, in-plane vortex, and fully three-dimensional vortex states. Phase diagrams show that these transitions are governed primarily by magnetostatic interactions, with stronger effects in Fe due to its higher saturation magnetization. These findings provide a strategy for deterministic remanent-state selection in square nanorings, relevant to multistate magnetic and spintronic applications.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"17 ","pages":"1-5"},"PeriodicalIF":1.1,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147665297","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}