Pub Date : 2024-09-13DOI: 10.1109/lmag.2024.3461575
Yassin Elmeligi, Bushra Hussain, Michael G. Cottam
{"title":"Role of Shape Ellipticity on Dipole-exchange Spin Waves in Ferromagnetic Nanorings","authors":"Yassin Elmeligi, Bushra Hussain, Michael G. Cottam","doi":"10.1109/lmag.2024.3461575","DOIUrl":"https://doi.org/10.1109/lmag.2024.3461575","url":null,"abstract":"","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2024-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142259502","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}
Pub Date : 2024-08-26DOI: 10.1109/lmag.2024.3450334
Martin Tkáč, Peter Kollár, Robert Maciaszek, Samuel Dobák, Ján Füzer, Denisa Olekšáková, Radovan Bureš, Mária Fáberová
{"title":"Effect of Powder Particle Surface Treatment on DC Magnetic Properties of Compacted Iron Cores","authors":"Martin Tkáč, Peter Kollár, Robert Maciaszek, Samuel Dobák, Ján Füzer, Denisa Olekšáková, Radovan Bureš, Mária Fáberová","doi":"10.1109/lmag.2024.3450334","DOIUrl":"https://doi.org/10.1109/lmag.2024.3450334","url":null,"abstract":"","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2024-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142193666","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}
Cu–Mn oxide spinels reveal notorious magnetocaloric performance at liquid nitrogen temperatures. We applied the soft chemistry sol–gel method to prepare Cu x Mn 3−x O 4 samples with nominal Cu content of x = 1, 1.5, 1.8, and 2. According to powder X-ray diffraction studies, we succeeded to fabricate multiphase samples with a high content of Cu in spinel phases. We provide insights into the structural and magnetic, as well as magnetocaloric, properties of the synthesized samples. We determine that in contrast to samples with x = 1.0 and 1.5, which are coupled ferromagnetically, the samples with x = 1.8 and 2.0 reveal ferrimagnetic coupling. The transition temperature is found to decrease only slightly from 78 K ( x = 1) to 75 K ( x = 2). The maximum values of the magnetic entropy change and relative cooling power are determined for each compound and found to be the largest for the sample with x = 1.0 due to its largest magnetization. Independent of the Cu content, here, the studied samples reveal a relative cooling power of larger than 139 J/kg, which highlights the relevance of these materials for magnetic refrigeration applications, particularly at liquid nitrogen temperatures.
铜锰氧化物尖晶石在液氮温度下具有显著的磁致性能。我们采用软化学溶胶-凝胶法制备了标称铜含量为 x = 1、1.5、1.8 和 2 的 CuxMn3-xO4 样品。根据粉末 X 射线衍射研究，我们成功制备出了尖晶石相中铜含量较高的多相样品。我们深入了解了合成样品的结构、磁性和磁致性。我们发现，与 x = 1.0 和 1.5 的铁磁耦合样品不同，x = 1.8 和 2.0 的样品具有铁磁耦合。过渡温度仅从 78 K（x = 1）略微下降到 75 K（x = 2）。确定了每种化合物的磁熵变化和相对冷却功率的最大值，发现 x = 1.0 的样品由于磁化最大而磁熵变化和相对冷却功率最大。与铜含量无关，所研究的样品显示出大于 139 J/kg 的相对冷却功率，这凸显了这些材料在磁制冷应用中的相关性，尤其是在液氮温度下。
{"title":"Exploring the Structural and Magnetic Properties of Cu-Rich CuxMn3−xO4 Spinels for Advanced Magnetic Refrigeration at Liquid Nitrogen Temperatures","authors":"Abir Hadded;Igor Veremchuk;Shengqiang Zhou;Denys Makarov;Essebti Dhahri","doi":"10.1109/LMAG.2024.3443745","DOIUrl":"https://doi.org/10.1109/LMAG.2024.3443745","url":null,"abstract":"Cu–Mn oxide spinels reveal notorious magnetocaloric performance at liquid nitrogen temperatures. We applied the soft chemistry sol–gel method to prepare Cu\u0000<italic><sub>x</sub></i>\u0000Mn\u0000<sub>3−</sub>\u0000<italic><sub>x</sub></i>\u0000O\u0000<sub>4</sub>\u0000 samples with nominal Cu content of \u0000<italic>x</i>\u0000 = 1, 1.5, 1.8, and 2. According to powder X-ray diffraction studies, we succeeded to fabricate multiphase samples with a high content of Cu in spinel phases. We provide insights into the structural and magnetic, as well as magnetocaloric, properties of the synthesized samples. We determine that in contrast to samples with \u0000<italic>x</i>\u0000 = 1.0 and 1.5, which are coupled ferromagnetically, the samples with \u0000<italic>x</i>\u0000 = 1.8 and 2.0 reveal ferrimagnetic coupling. The transition temperature is found to decrease only slightly from 78 K (\u0000<italic>x</i>\u0000 = 1) to 75 K (\u0000<italic>x</i>\u0000 = 2). The maximum values of the magnetic entropy change and relative cooling power are determined for each compound and found to be the largest for the sample with \u0000<italic>x</i>\u0000 = 1.0 due to its largest magnetization. Independent of the Cu content, here, the studied samples reveal a relative cooling power of larger than 139 J/kg, which highlights the relevance of these materials for magnetic refrigeration applications, particularly at liquid nitrogen temperatures.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2024-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142174007","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}
Pub Date : 2024-07-18DOI: 10.1109/LMAG.2024.3430189
Susheel K. Arya;Sonalie Ahirwar;Tanmoy Pramanik
External magnetic field perturbation remains a key reliability issue for spin-transfer-torque magnetic random-access memory. Although several prototypes have been demonstrated already, the effects of external fields with varying directions are not well reported. Our macrospin-based study revealed a significant increase in write failures in the presence of small off-axis external magnetic fields. However, incoherent switching pathways, which are also known to impact the switching process, cannot be captured by a macrospin model. Here, we report the micromagnetic model study of the switching process of perpendicular nanomagnets in the presence of magnetic fields of varying magnitudes and directions. The results are consistent with the macrospin model prediction for smaller magnet sizes. For larger magnet sizes, the impact of the off-axis external magnetic field becomes much worse when incoherent magnetization modes dominate the switching process.
{"title":"Impact of Off-Axis External Magnetic Field Perturbation on the Write Error Slopes of Perpendicular STT-RAM Cell: Micromagnetic Study","authors":"Susheel K. Arya;Sonalie Ahirwar;Tanmoy Pramanik","doi":"10.1109/LMAG.2024.3430189","DOIUrl":"10.1109/LMAG.2024.3430189","url":null,"abstract":"External magnetic field perturbation remains a key reliability issue for spin-transfer-torque magnetic random-access memory. Although several prototypes have been demonstrated already, the effects of external fields with varying directions are not well reported. Our macrospin-based study revealed a significant increase in write failures in the presence of small off-axis external magnetic fields. However, incoherent switching pathways, which are also known to impact the switching process, cannot be captured by a macrospin model. Here, we report the micromagnetic model study of the switching process of perpendicular nanomagnets in the presence of magnetic fields of varying magnitudes and directions. The results are consistent with the macrospin model prediction for smaller magnet sizes. For larger magnet sizes, the impact of the off-axis external magnetic field becomes much worse when incoherent magnetization modes dominate the switching process.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2024-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141738173","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}
Pub Date : 2024-06-18DOI: 10.1109/LMAG.2024.3416091
Andre Dubovskiy;Troy Criss;Ahmed Sidi El Valli;Laura Rehm;Andrew D. Kent;Andrew Haas
Large quantities of random numbers are crucial in a wide range of applications. We have recently demonstrated that perpendicular nanopillar magnetic tunnel junctions (pMTJs) can produce true random bits when actuated with short pulses. However, our implementation used high-end and expensive electronics, such as a high-bandwidth arbitrary waveform generator and analog-to-digital converter, and was limited to relatively low data rates. Here, we significantly increase the speed of true random-number generation of our stochastic actuated pMTJs (SMART-pMTJs) using field-programmable gate arrays (FPGAs), demonstrating the generation of over ${text{10}}^{text{12}}$ bits at rates exceeding 10 Mb/s. The resulting bitstreams pass the NIST Statistical Test Suite for randomness with only one xor operation. In addition to a hundred-fold reduction in the setup cost and a thousand-fold increase in bitrate, the advancement includes simplifying and optimizing random bit generation with a custom-designed analog daughterboard to interface an FPGA and SMART-pMTJ. The resulting setup further enables FPGA at-speed processing of MTJ data for stochastic modeling and cryptography.
{"title":"One Trillion True Random Bits Generated With a Field-Programmable Gate Array Actuated Magnetic Tunnel Junction","authors":"Andre Dubovskiy;Troy Criss;Ahmed Sidi El Valli;Laura Rehm;Andrew D. Kent;Andrew Haas","doi":"10.1109/LMAG.2024.3416091","DOIUrl":"10.1109/LMAG.2024.3416091","url":null,"abstract":"Large quantities of random numbers are crucial in a wide range of applications. We have recently demonstrated that perpendicular nanopillar magnetic tunnel junctions (pMTJs) can produce true random bits when actuated with short pulses. However, our implementation used high-end and expensive electronics, such as a high-bandwidth arbitrary waveform generator and analog-to-digital converter, and was limited to relatively low data rates. Here, we significantly increase the speed of true random-number generation of our stochastic actuated pMTJs (SMART-pMTJs) using field-programmable gate arrays (FPGAs), demonstrating the generation of over \u0000<inline-formula><tex-math>${text{10}}^{text{12}}$</tex-math></inline-formula>\u0000 bits at rates exceeding 10 Mb/s. The resulting bitstreams pass the NIST Statistical Test Suite for randomness with only one \u0000<sc>xor</small>\u0000 operation. In addition to a hundred-fold reduction in the setup cost and a thousand-fold increase in bitrate, the advancement includes simplifying and optimizing random bit generation with a custom-designed analog daughterboard to interface an FPGA and SMART-pMTJ. The resulting setup further enables FPGA at-speed processing of MTJ data for stochastic modeling and cryptography.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2024-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10561576","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141934040","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}
In recent years, there have been significant advancements in the manufacturing of emerging technologies, especially in the areas of in-memory computing and neural networks, which are currently some of the most actively researched topics. With the increasing need to process complex tasks, the development of intelligent processors has become more crucial than ever. This letter advances a high-capacity spintronic synapse using magnetic tunnel junctions (MTJs) and carbon nanotube field-effect transistors (CNTFETs) to implement associative memory. The choice of MTJ devices is due to their remarkable features, including reliable reconfiguration and nonvolatility. Moreover, CNTFETs have overcome traditional complementary metal–oxide semiconductor limitations, such as the short-channel effect and suboptimal hole mobility. The design seeks to improve accuracy and memory capacity by increasing the number of weights. Simulation results indicate that the design offers a 19%–73% higher number of weights and a lower error rate than the state-of-the-art counterparts.
{"title":"A Multiplexer-Based High-Capacity Spintronic Synapse","authors":"Mahan Rezaei;Ermia Elahi;Arefe Amirany;Mohammad Hossein Moaiyeri","doi":"10.1109/LMAG.2024.3416092","DOIUrl":"10.1109/LMAG.2024.3416092","url":null,"abstract":"In recent years, there have been significant advancements in the manufacturing of emerging technologies, especially in the areas of in-memory computing and neural networks, which are currently some of the most actively researched topics. With the increasing need to process complex tasks, the development of intelligent processors has become more crucial than ever. This letter advances a high-capacity spintronic synapse using magnetic tunnel junctions (MTJs) and carbon nanotube field-effect transistors (CNTFETs) to implement associative memory. The choice of MTJ devices is due to their remarkable features, including reliable reconfiguration and nonvolatility. Moreover, CNTFETs have overcome traditional complementary metal–oxide semiconductor limitations, such as the short-channel effect and suboptimal hole mobility. The design seeks to improve accuracy and memory capacity by increasing the number of weights. Simulation results indicate that the design offers a 19%–73% higher number of weights and a lower error rate than the state-of-the-art counterparts.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2024-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141934114","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}
During the service of an HP tube, carbon diffuses into the tube wall, forming a carburization layer and reducing the mechanical strength. To quantitatively measure the carburization layer thickness, its magnetic properties should be accurately characterized. Magnetic properties, including saturation magnetization and magnetic permeability, of chromium-depleted HP alloy have been characterized by a vibration sample magnetometer and the eddy current method. The microstructural observations were made using optical microscopy and scanning electron microscopy. The change of the magnetic properties with chromium content has been quantitatively obtained. The results show that the saturated mass magnetization and magnetic permeability have abrupt increases when chromium content is less than 14.6% and 11.8%, respectively. The obtained properties were further used to quantitatively evaluate the carburization layer thickness in a slice of ex-serviced tube. The estimation error was less than 0.33 mm, indicating the characterized magnetic properties are effective for the carburization layer measurement.
HP 管在使用过程中，碳会扩散到管壁，形成渗碳层，降低机械强度。要定量测量渗碳层厚度，就必须准确表征其磁性能。我们采用振动样品磁力计和涡流法对贫铬 HP 合金的磁性能（包括饱和磁化和磁导率）进行了表征。使用光学显微镜和扫描电子显微镜对微观结构进行了观察。定量分析了磁性能随铬含量的变化。结果表明，当铬含量低于 14.6% 和 11.8% 时，饱和磁化率和磁导率会突然增加。获得的特性被进一步用于定量评估退役钢管切片的渗碳层厚度。估算误差小于 0.33 毫米，表明所表征的磁性能对渗碳层测量有效。
{"title":"Magnetic and Microstructural Characterization of Carburized 25Cr35NiNb Alloy","authors":"Shukai Chen;Minghao Zhang;Ke Huang;Genghao Jiao;Yihua Kang;Bo Feng","doi":"10.1109/LMAG.2024.3376152","DOIUrl":"10.1109/LMAG.2024.3376152","url":null,"abstract":"During the service of an HP tube, carbon diffuses into the tube wall, forming a carburization layer and reducing the mechanical strength. To quantitatively measure the carburization layer thickness, its magnetic properties should be accurately characterized. Magnetic properties, including saturation magnetization and magnetic permeability, of chromium-depleted HP alloy have been characterized by a vibration sample magnetometer and the eddy current method. The microstructural observations were made using optical microscopy and scanning electron microscopy. The change of the magnetic properties with chromium content has been quantitatively obtained. The results show that the saturated mass magnetization and magnetic permeability have abrupt increases when chromium content is less than 14.6% and 11.8%, respectively. The obtained properties were further used to quantitatively evaluate the carburization layer thickness in a slice of ex-serviced tube. The estimation error was less than 0.33 mm, indicating the characterized magnetic properties are effective for the carburization layer measurement.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2024-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140169211","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}
The read reliability of spin-transfer torque magnetic random-access memory (STT-MRAM) is greatly hindered by a low sensing margin as a result of a small tunneling magnetoresistance ratio. Although the new generation of perpendicular anisotropy spin-orbit torque (SOT)-MRAM offers faster access speed and a longer lifetime than STT-MRAM, its read performance has not improved or even deteriorated because of the additional resistance of the SOT channel in the read path. In this letter, we propose two novel cell structures of SOT-MRAM that consist of one/two transistors, two diodes, and two magnetic tunnel junctions (1T2D2MTJ/2T2D2MTJ) on a shared U-shaped antiferromagnet layer, enabling a self-referencing scheme. Thanks to the bent current channel, the opposite direction of the SOT current below the free layers can one-step switch different data states in compatibility with the existing fabrication process of SOT-MRAM. Combined with the 28 nm tech node and Verilog-A MTJ compact model, the simulation results show that our MRAM cell significantly improves the sensing margin and bit error rate over the conventional two transistors and one MTJ (2T1M) cell, which is expected to become a high read performance solution.
自旋转移力矩磁性随机存取存储器（STT-MRAM）的读取可靠性因隧道磁阻比小而感应裕度低而大受影响。虽然新一代垂直各向异性自旋轨道力矩（SOT）-MRAM 比 STT-MRAM 具有更快的存取速度和更长的使用寿命，但由于 SOT 通道在读取路径中的附加电阻，其读取性能并未得到改善，甚至有所下降。在这封信中，我们提出了两种新型 SOT-MRAM 单元结构，它们由一个/两个晶体管、两个二极管和两个磁隧道结（1T2D2MTJ/2T2D2MTJ）组成，位于一个共享的 U 型反铁磁体层上，从而实现了自参照方案。得益于弯曲的电流通道，自由层下的 SOT 电流的相反方向可以一步切换不同的数据状态，与现有的 SOT-MRAM 制造工艺兼容。结合 28 纳米技术节点和 Verilog-A MTJ 紧凑型模型，仿真结果表明，与传统的两个晶体管和一个 MTJ（2T1M）单元相比，我们的 MRAM 单元显著提高了传感裕度和误码率，有望成为一种高读取性能解决方案。
{"title":"Complementary-Magnetization-Switching Perpendicular Spin-Orbit Torque Random-Access Memory Cell for High Read Performance","authors":"Hao Zhang;Di Wang;Long Liu;Yu Liu;Huai Lin;Yifan Zhang;Changqing Xie","doi":"10.1109/LMAG.2024.3396750","DOIUrl":"10.1109/LMAG.2024.3396750","url":null,"abstract":"The read reliability of spin-transfer torque magnetic random-access memory (STT-MRAM) is greatly hindered by a low sensing margin as a result of a small tunneling magnetoresistance ratio. Although the new generation of perpendicular anisotropy spin-orbit torque (SOT)-MRAM offers faster access speed and a longer lifetime than STT-MRAM, its read performance has not improved or even deteriorated because of the additional resistance of the SOT channel in the read path. In this letter, we propose two novel cell structures of SOT-MRAM that consist of one/two transistors, two diodes, and two magnetic tunnel junctions (1T2D2MTJ/2T2D2MTJ) on a shared U-shaped antiferromagnet layer, enabling a self-referencing scheme. Thanks to the bent current channel, the opposite direction of the SOT current below the free layers can one-step switch different data states in compatibility with the existing fabrication process of SOT-MRAM. Combined with the 28 nm tech node and Verilog-A MTJ compact model, the simulation results show that our MRAM cell significantly improves the sensing margin and bit error rate over the conventional two transistors and one MTJ (2T1M) cell, which is expected to become a high read performance solution.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2024-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140842453","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}
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