IEEE Magnetics Letters最新文献

{"title":"Iterative Multihead Multitrack Detection Scheme for Bit-Patterned Media Recording","authors":"Gyuyeol Kong;Taehyoung Kim;Minchae Jung","doi":"10.1109/LMAG.2022.3219234","DOIUrl":"https://doi.org/10.1109/LMAG.2022.3219234","url":null,"abstract":"An iterative multihead multitrack detection scheme for bit-patterned media recording is described in this letter. The scheme employs two iterative strategies with multihead, multitrack detection where three tracks are simultaneously processed to accurately estimate the channel with track misregistration (TMR) and effectively detect the data by using intertrack interference (\u0000<bold>ITI</b>\u0000) information with high reliability. The first outer iteration aims to compensate for the TMR effect, and the second inner iteration aims to improve the reliability of the data. In the outer iteration, the TMR effect is compensated by modifying the generalized partial response (GPR) target to a channel that reflects the TMR estimated by a TMR estimator using an expectation and maximization algorithm. In the inner iteration, iterative equalization and decoding (IED) is conducted between the two-dimensional partial response maximum-likelihood detector and the low-density parity check decoder based on the revised GPR target. Since each track has a different channel performance according to the amount of ITI information in the multitrack detection, we design the GPR target and the code rate separately for each track to maximize the overall channel performance. The bit error rate performances of the proposed IED scheme are compared with the conventional IED scheme when the areal density is 2 \u0000<inline-formula><tex-math>$text{Tb/in}^{2}$</tex-math></inline-formula>\u0000. Simulation results show that the IED scheme has more than 2 dB gain compared with the conventional IED scheme for 30\u0000<inline-formula><tex-math>$%$</tex-math></inline-formula>\u0000 TMR.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2022-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67741659","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":"Experimental Demonstration of a Spin-Wave Lens Designed With Machine Learning","authors":"Martina Kiechle;Levente Maucha;Valentin Ahrens;Carsten Dubs;Wolfgang Porod;Gyorgy Csaba;Markus Becherer;Adam Papp","doi":"10.1109/LMAG.2022.3209647","DOIUrl":"https://doi.org/10.1109/LMAG.2022.3209647","url":null,"abstract":"In this letter, we present the design and experimental realization of a device that acts like a spin-wave lens i.e., it focuses spin waves to a specified location. The structure of the lens does not resemble any conventional lens design. It is a nonintuitive pattern produced by a machine-learning algorithm. As a spin-wave design tool, we used our custom micromagnetic solver SpinTorch, which has built-in automatic gradient calculation and can perform backpropagation through time for spin-wave propagation. The training itself is performed with the saturation magnetization of a yttrium-iron-garnet (YIG) film as a variable parameter, with the goal to guide spin waves to a predefined location. We verified the operation of the device in the widely used mumax\u0000<inline-formula><tex-math>$^{3}$</tex-math></inline-formula>\u0000 micromagnetic solver, and by experimental realization. For the experimental implementation, we developed a technique to create effective saturation-magnetization landscapes in YIG by direct focused-ion-beam (FIB) irradiation. This allows us to rapidly transfer the nanoscale design patterns to the YIG medium, without patterning the material by etching. We measured the effective saturation magnetization corresponding to the FIB dose levels in advance and used this mapping to translate the designed scatterer to the required dose levels. Our demonstration serves as a proof of concept for a workflow that can be used to realize more sophisticated spin-wave devices with complex functionality, e.g., spin-wave signal processors, or neuromorphic devices.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2022-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67741658","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":"Novel Magnetic Localization Methods for Minimizing the Ellipse Error Based on Tensor Invariants","authors":"Xiangang Li;Shenggang Yan;Jianguo Liu;Youyu Yan","doi":"10.1109/LMAG.2022.3205881","DOIUrl":"https://doi.org/10.1109/LMAG.2022.3205881","url":null,"abstract":"There are various technology routes for the localization of magnetic targets. Among them, localization methods based on magnetic gradient tensor invariants have remarkable preponderance. For instance, such invariants are not sensitive to the jitter of the coordinate system, which means this kind of method can be very suitable for application in moving carriers. The traditional classic method contains ellipse error, which cannot be simply ignored. In order to eliminate this error, the general solution of the location vector is derived in this letter. Three methods for solving the general solution are given. To validate the effectiveness of the methods, the localization problem of the measurement array surrounding a static target is simulated. In this simulation, the localization results of the traditional method and the proposed methods are analyzed and compared. The conclusions show that the developed methods successfully remove the ellipse error and improve the localization accuracy.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2022-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67902598","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":"Robustness of Binary Stochastic Neurons Implemented With Low Barrier Nanomagnets Made of Dilute Magnetic Semiconductors","authors":"Rahnuma Rahman;Supriyo Bandyopadhyay","doi":"10.1109/LMAG.2022.3202135","DOIUrl":"https://doi.org/10.1109/LMAG.2022.3202135","url":null,"abstract":"Binary stochastic neurons (BSNs) are excellent hardware accelerators for machine learning. A popular platform for implementing them is low- or zero-energy barrier nanomagnets possessing in-plane magnetic anisotropy (e.g., circular disks or quasi-elliptical disks with very small eccentricity). Unfortunately, small geometric variations in the lateral shapes of such nanomagnets can produce large changes in the BSN response times if the nanomagnets are made of common metallic ferromagnets (Co, Ni, Fe) with large saturation magnetization. In addition, the response times become very sensitive to initial conditions, i.e., the initial magnetization orientation. In this letter, we show that if the nanomagnets are made of dilute magnetic semiconductors with much smaller saturation magnetization than common metallic ferromagnets, then the variability in their response times (due to shape variations and variation in the initial condition) is drastically suppressed. This significantly reduces the device-to-device variation, which is a serious challenge for large-scale neuromorphic systems. A simple material choice can, therefore, alleviate one of the most aggravating problems in probabilistic computing with nanomagnets.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2022-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67902601","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":"Theoretical Circuit Design of an Efficient Spintronic Random Number Generator With an Internal Postprocessing Unit","authors":"Saeed Mehri;Abdolah Amirany;Mohammad Hossein Moaiyeri;Kian Jafari","doi":"10.1109/LMAG.2022.3200326","DOIUrl":"https://doi.org/10.1109/LMAG.2022.3200326","url":null,"abstract":"In this letter, a spintronic true random number generator (TRNG) is designed using the stochastic switching feature of the magnetic tunnel junction device in the subcritical current regime. The proposed structure consumes low power and occupies a small area. Also, to improve the quality of random numbers production and compensate for the impact of process variations on the quality of the random output, the proposed TRNG includes an internal postprocessing unit. Compared to state-of-the-art designs, using an internal postprocessing unit reduces the proposed generator's area overhead and power consumption. The simulation results show that the TRNG proposed in this letter consumes up to 68% less power and occupies up to 64% smaller area than the state-of-the-art design. Also, due to the existence of the efficient postprocessing unit, the proposed TRNG successfully passes the National Institute of Standards and Technology random number tests even in the presence of the fabrication process variations.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2022-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67740925","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":"Longitudinal Transformation of Magnetic Properties in Magnetic Microwires With Graded Magnetic Anisotropy","authors":"Alexander Chizhik;Paula Corte-León;Valentina Zhukova;Julian Gonzalez;Arcady Zhukov","doi":"10.1109/LMAG.2022.3199170","DOIUrl":"https://doi.org/10.1109/LMAG.2022.3199170","url":null,"abstract":"We studied the magneto-optical and magnetic behavior of Co- and Fe-rich microwires that were stress-annealed at temperatures distributed along the microwire length. There was a transformation of the magnetic structure across zones subjected to annealing at different temperatures. Differences in the magnetic behavior between the surface and bulk were observed for both Co- and Fe-rich microwires. The formation and subsequent transformation of a helical magnetic structure were observed, depending on the type of microwire. Annealing at temperatures below 100 °C affected the magnetic system of microwires. This effect is due to a weak but noticeable relaxation of the initial stresses in all parts of the microwire that even occurs in the low temperature range.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2022-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67741242","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":"Safety Assessment of H-Coil for Nursing Staff in Deep Transcranial Magnetic Stimulation","authors":"Mai Lu;Shoogo Ueno","doi":"10.1109/LMAG.2022.3198370","DOIUrl":"https://doi.org/10.1109/LMAG.2022.3198370","url":null,"abstract":"This work investigates the exposure experienced by the nursing staff executing deep transcranial magnetic stimulations (TMS) using H-coil. The safety assessment was implemented by employing the H-coil and realistic human model. The 144 relative positions of the H-coil with respect to the TMS operator body were considered, including the distance and vertical height. Dependence of the magnetic flux density and induced electric fields in the human model were obtained by using the impedance method. Results were compared with the International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines. Regarding the occupational exposure, safe distances of 120 and 100 cm are derived from the ICNIRP reference level (RL) and basic restriction (BR), respectively. At the distance of 100 cm, the exposure level does not exceed the ICNIRP BR, and although the exposure level exceeds the RL, continued exposure is allowed. The findings suggest that nursing staff should stand at least 100 cm apart from the H-coil.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2022-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/iel7/5165412/9656771/09857568.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67741202","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":"Simulation of Magnetic Resonance Sounding With a Delayed Adiabatic Pulse","authors":"Benquan Yang;Yujing Yang","doi":"10.1109/LMAG.2022.3196597","DOIUrl":"https://doi.org/10.1109/LMAG.2022.3196597","url":null,"abstract":"Magnetic resonance sounding (MRS) is used to identify groundwater by exciting and measuring the nuclear magnetic resonance of hydrogen nuclei in subsurface aquifers. However, the MRS response is particularly weak and has a low signal-to-noise ratio (SNR); therefore, signal enhancement methods, such as adiabatic pulses, are essential for MRS applications with strong interference. The key challenges of utilizing this novel method are to increase the MRS signal response and sensitivity for field measurements. In this letter, we present an improved transmitting mode of a commonly used adiabatic half-passage pulse by combining this pulse with an earlier fixed frequency off-resonant pulse of short duration, thereby increasing the theoretical MRS sensitivity. Simulation results demonstrate that the approach could be used to further improve the signal responses, i.e., in terms of the SNR and potential resolution, for MRS exploration of high-noise environments.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2022-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67902596","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":"Two Modes of Drag Reduction for Magnetorheological Fluids","authors":"Jing Cheng Lv;Ming Yu Wu;Tong Zhao;Yin Tao Wei","doi":"10.1109/LMAG.2022.3193954","DOIUrl":"https://doi.org/10.1109/LMAG.2022.3193954","url":null,"abstract":"Magnetorheological fluids (MRFs) show a millisecond-level reversible response controlled by an external magnetic field and are, thus, widely used in many areas, especially vehicle dampers, clutches, and brakes. However, in the standby state, the piston or rotor of these devices still moves in the MRF and generates damping force or torque, which will deteriorate the performance and even significantly increase the energy consumption of the entire vehicle. To solve these problems, we propose two working modes of MRFs based on rheology: vertical shear and parallel shear modes. We designed relevant magnetic circuit implementations for drum-type rotary magnetorheological (MR) devices to realize these new modes and verified the drag reduction effects by using a modified rheometer. The experimental results indicate that the vertical shear and parallel shear modes reduce the drag torque of the MRF by approximately 10% and 9% at magnetic field strengths of approximately 3.5 and 0.1 kA/m, respectively. Therefore, MR devices utilizing these drag reduction modes can reduce standby damping to improve performance. In addition, two mechanisms were developed to explain the significant decrease in damping torque with the increasing number of experiments under the vertical shear mode. In summary, research into these two modes promotes understanding of MRFs and the development of MR devices.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2022-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67741204","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":"Construction of Energy Loops Using Magnetic Barkhausen Noise","authors":"Xiaoge Meng;Lin Li;Yanzhao Hou","doi":"10.1109/LMAG.2022.3191281","DOIUrl":"https://doi.org/10.1109/LMAG.2022.3191281","url":null,"abstract":"Magnetic Barkhausen noise (MBN), which contains microstructure information of materials, is widely used in nondestructive testing (NDT) of magnetic materials. MBN energy (MBN\u0000_energy\u0000) is a time-independent indicator for NDT, but the initial MBN\u0000_energy\u0000 has no clear physical meaning and cannot be used to explain the relationship to the hysteresis loop. In this letter, based on the physical mechanism of MBN, a proportional relation is built between the MBN voltage signal \u0000<italic>V</i>\u0000_B\u0000 and energy loss, and the signal \u0000<italic>V</i>\u0000_B\u0000 is then related to the energy loss through wall pinning in the Jiles–Atherton hysteresis model. We define a novel magnetic Barkhausen noise energy eigenvalue (MBNE\u0000<italic>)</i>\u0000 as the time integral of the product of the absolute value of \u0000<italic>V</i>\u0000_B\u0000 and the sign function sign(\u0000<italic>dH</i>\u0000/\u0000<italic>dt</i>\u0000). We prove that the MBNE is proportional to the irreversible magnetization \u0000<italic>M</i>\u0000_irr\u0000. Since \u0000<italic>M</i>\u0000_irr\u0000 is equal to the saturation magnetization \u0000<italic>M</i>\u0000_s\u0000 when the magnetization of ferromagnetic material reaches saturation, we scaled the MBNE to make its maximum value equal to \u0000<italic>M</i>\u0000_s\u0000 and found that MBNE with respect to the magnetic field \u0000<italic>H</i>\u0000, MBNE(\u0000<italic>H</i>\u0000), coincides with the irreversible hysteresis loop \u0000<italic>M</i>\u0000_irr\u0000(\u0000<italic>H</i>\u0000). We refer to MBNE(\u0000<italic>H</i>\u0000) as the MBN energy loop. The MBNE(\u0000<italic>H</i>\u0000) and \u0000<italic>M</i>\u0000_irr\u0000(\u0000<italic>H</i>\u0000) for two kinds of electrical steel sheets are compared experimentally, which validates the adaptability of the MBNE(\u0000<italic>H</i>\u0000) construction method. The method to obtain \u0000<italic>M</i>\u0000_irr\u0000(\u0000<italic>H</i>\u0000) from the MBN raw signal reveals the physical mechanism of MBN and the irreversible magnetization process of magnetic materials.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2022-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67741215","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}