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":"15 ","pages":"1-4"},"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":"15 ","pages":"1-5"},"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":"15 ","pages":"1-5"},"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":"15 ","pages":"1-5"},"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}
Pub Date : 2024-02-28DOI: 10.1109/LMAG.2024.3371370
Wesley Lawson
We describe the design and preliminary testing of a portable single-pulse transcranial magnetic stimulation (sTMS) device for the possible treatment of migraine headaches. The design requirements are presented, and tradeoffs/options for some of the key components are analyzed. Details of the design are given, and performance results of the initial prototype are compared with the theoretical predictions, demonstrating the viability of the design.
{"title":"Design and Testing of a Compact, Portable Single-Pulse Transcranial Magnetic Stimulation Device","authors":"Wesley Lawson","doi":"10.1109/LMAG.2024.3371370","DOIUrl":"10.1109/LMAG.2024.3371370","url":null,"abstract":"We describe the design and preliminary testing of a portable single-pulse transcranial magnetic stimulation (sTMS) device for the possible treatment of migraine headaches. The design requirements are presented, and tradeoffs/options for some of the key components are analyzed. Details of the design are given, and performance results of the initial prototype are compared with the theoretical predictions, demonstrating the viability of the design.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"15 ","pages":"1-5"},"PeriodicalIF":1.2,"publicationDate":"2024-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140011487","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}
This letter proposes a single event upset (SEU)-hardened task-scheduling logic-in-memory xnor/xor neuron and synapse circuit. Using a C-element and a magnetic tunnel junction enhances immunity against SEU injection. Also, using logic-in-memory architecture eliminates the need to access external memory and decreases power and delay. Furthermore, using a carbon nanotube field-effect transistor leads to lower leakage and static current caused by higher gate control in these transistors. Compared to the state-of-the-art counterparts, the developed design offers at least 31%, 17%, and 3% improvement in power, power delay product, and power delay area product, respectively.
这封信提出了一种单事件干扰（SEU）加固的任务调度逻辑内存 xnor/xor 神经元和突触电路。使用 C 元素和磁隧道结增强了对 SEU 注入的免疫力。同时，使用内存逻辑架构无需访问外部存储器，从而降低了功耗和延迟。此外，使用碳纳米管场效应晶体管可降低漏电流和静态电流，因为这些晶体管的栅极控制能力更强。与最先进的同类产品相比，所开发的设计在功率、功率延迟积和功率延迟面积积方面分别至少提高了 31%、17% 和 3%。
{"title":"Radiation-Immune Spintronic Binary Synapse and Neuron for Process-in-Memory Architecture","authors":"Milad Tanavardi Nasab;Abdolah Amirany;Mohammad Hossein Moaiyeri;Kian Jafari","doi":"10.1109/LMAG.2024.3356815","DOIUrl":"10.1109/LMAG.2024.3356815","url":null,"abstract":"This letter proposes a single event upset (SEU)-hardened task-scheduling logic-in-memory \u0000<sc>xnor/xor</small>\u0000 neuron and synapse circuit. Using a C-element and a magnetic tunnel junction enhances immunity against SEU injection. Also, using logic-in-memory architecture eliminates the need to access external memory and decreases power and delay. Furthermore, using a carbon nanotube field-effect transistor leads to lower leakage and static current caused by higher gate control in these transistors. Compared to the state-of-the-art counterparts, the developed design offers at least 31%, 17%, and 3% improvement in power, power delay product, and power delay area product, respectively.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"15 ","pages":"1-5"},"PeriodicalIF":1.2,"publicationDate":"2024-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139950941","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 : 2024-01-05DOI: 10.1109/LMAG.2024.3350438
Charlie Jindrich;Qi Shao;Antonio Ruotolo
Theoretical studies show that metastable phases of nonmagnetic oxides could exhibit magnetic order when synthesized in two-dimensional (2-D) atomic crystals. In this letter, we report experimental evidence of a nontrivial antiferromagnetic behavior in a 2-D, metastable phase of iridium oxide in which iridium forms a triangular lattice. We compare the magnetic behavior of the crystals in the morphology of 2-D nanosheets with that of the same crystals in the morphology of nanoparticles. At low temperatures, the magnetic moment of nanosheets exceeds that of the nanoparticles while coercivity and remanence collapse, suggesting a transition to an antiferromagnetic phase. Morphology at the nanoscale seems to play a significant role in the magnetic behavior of oxide semiconductors.
{"title":"Antiferromagnetism in Two-Dimensional, 1T-Phase Iridium Oxide","authors":"Charlie Jindrich;Qi Shao;Antonio Ruotolo","doi":"10.1109/LMAG.2024.3350438","DOIUrl":"https://doi.org/10.1109/LMAG.2024.3350438","url":null,"abstract":"Theoretical studies show that metastable phases of nonmagnetic oxides could exhibit magnetic order when synthesized in two-dimensional (2-D) atomic crystals. In this letter, we report experimental evidence of a nontrivial antiferromagnetic behavior in a 2-D, metastable phase of iridium oxide in which iridium forms a triangular lattice. We compare the magnetic behavior of the crystals in the morphology of 2-D nanosheets with that of the same crystals in the morphology of nanoparticles. At low temperatures, the magnetic moment of nanosheets exceeds that of the nanoparticles while coercivity and remanence collapse, suggesting a transition to an antiferromagnetic phase. Morphology at the nanoscale seems to play a significant role in the magnetic behavior of oxide semiconductors.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"15 ","pages":"1-4"},"PeriodicalIF":1.2,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139694981","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 : 2024-01-05DOI: 10.1109/LMAG.2024.3350428
Mahieddine Lahoubi;Shengli Pu;Weinan Liu;Zhe Yang
In this letter, we report anomalous magnetic properties in high dc magnetic fields H up to 11 and 16 T from 1.35 up to 20 K on PrBa 2 Cu 3 O 6.95 (PrBCO 6.95 ) cuprate ceramic. Significant magnetic-field effects are revealed in the derivative of the magnetization M ( T ) versus T using two sets of values of H selected in the range of 2.5–9.5 T. Anomalies are observed at the low-critical point T cr = 4–5 K, in the region of the spin reorientation phase transition temperature T 2 = 10.5 K, and around the Néel temperature of the antiferromagnetic ordering of the Pr 3+ sublattice T N = 14 K. Using Arrott plot analysis, we identified weak field-induced phase transitions at two critical fields, H cr1 ( T ) ∼ 3.3 T and H cr2 ( T ) ∼ 7.5 T, whose associated transition lines exhibit an almost temperature-independent behavior in the range 1.35 K- T 2 , and seem to vanish in the vicinity of T N . When T decreases from 20 K, an increase occurs in the derivative of the magnetization M ( H ) versus H for 0.5 T < H < 1 T, as well as in the differential susceptibility χ d ( T ) versus T where a shape change occurs when crossing T cr . The spontaneous magnetization M S ( T ), which was deduced by extrapolation to zero-field from the field-linear regime up to 2 T, shows an inverse variation with T and a shape change when crossing T N and T 2 . These features, which are taken as evidence for an additional weak ferromagnetic-like component that survives above T N , result from the significant role of the Pr-Cu(2) magnetic coupling.
在这封信中，我们报告了 PrBa2Cu3O6.95 (PrBCO6.95) 铜氧化物陶瓷在 1.35 至 20 K 高直流磁场 H 达 11 和 16 T 时的异常磁性能。在低临界点 Tcr = 4-5 K、自旋重新定向相变温度 T2 = 10.利用阿罗特图分析，我们确定了在两个临界场 Hcr1(T) ∼ 3.3 T 和 Hcr2(T) ∼ 7.5 T 处的弱场诱导相变，其相关的过渡线在 1.35 K-T2 范围内表现出几乎与温度无关的行为，并且似乎在 TN 附近消失。当 T 从 20 K 开始降低时，磁化 M(H) 相对于 H 的导数（0.5 T < H < 1 T）以及相对于 T 的差分磁感应强度 χd(T)都会增加。自发磁化 MS(T) 是通过从场-线性机制推断出的零场，最高可达 2 T，显示出随 T 的反向变化，以及在跨越 TN 和 T2 时的形状变化。这些特征被认为是在 TN 以上存在一个额外的弱铁磁样成分的证据，是 Pr-Cu(2) 磁耦合的重要作用所致。
{"title":"Magnetic Field-Induced Phase Transition and Weak Ferromagnetism in Nonsuperconducting Optimally Doped PrBCO Cuprate","authors":"Mahieddine Lahoubi;Shengli Pu;Weinan Liu;Zhe Yang","doi":"10.1109/LMAG.2024.3350428","DOIUrl":"10.1109/LMAG.2024.3350428","url":null,"abstract":"In this letter, we report anomalous magnetic properties in high dc magnetic fields \u0000<italic>H</i>\u0000 up to 11 and 16 T from 1.35 up to 20 K on PrBa\u0000<sub>2</sub>\u0000Cu\u0000<sub>3</sub>\u0000O\u0000<sub>6.95</sub>\u0000 (PrBCO\u0000<sub>6.95</sub>\u0000) cuprate ceramic. Significant magnetic-field effects are revealed in the derivative of the magnetization \u0000<italic>M</i>\u0000(\u0000<italic>T</i>\u0000) versus \u0000<italic>T</i>\u0000 using two sets of values of \u0000<italic>H</i>\u0000 selected in the range of 2.5–9.5 T. Anomalies are observed at the low-critical point \u0000<italic>T</i>\u0000<sub>cr</sub>\u0000 = 4–5 K, in the region of the spin reorientation phase transition temperature \u0000<italic>T</i>\u0000<sub>2</sub>\u0000 = 10.5 K, and around the Néel temperature of the antiferromagnetic ordering of the Pr\u0000<sup>3+</sup>\u0000 sublattice \u0000<italic>T</i>\u0000<sub>N</sub>\u0000 = 14 K. Using Arrott plot analysis, we identified weak field-induced phase transitions at two critical fields, \u0000<italic>H</i>\u0000<sub>cr1</sub>\u0000(\u0000<italic>T</i>\u0000) ∼ 3.3 T and \u0000<italic>H</i>\u0000<sub>cr2</sub>\u0000(\u0000<italic>T</i>\u0000) ∼ 7.5 T, whose associated transition lines exhibit an almost temperature-independent behavior in the range 1.35 K-\u0000<italic>T</i>\u0000<sub>2</sub>\u0000, and seem to vanish in the vicinity of \u0000<italic>T</i>\u0000<sub>N</sub>\u0000. When \u0000<italic>T</i>\u0000 decreases from 20 K, an increase occurs in the derivative of the magnetization \u0000<italic>M</i>\u0000(\u0000<italic>H</i>\u0000) versus \u0000<italic>H</i>\u0000 for 0.5 T < \u0000<italic>H</i>\u0000 < 1 T, as well as in the differential susceptibility \u0000<italic>χ</i>\u0000<sub>d</sub>\u0000(\u0000<italic>T</i>\u0000) versus \u0000<italic>T</i>\u0000 where a shape change occurs when crossing \u0000<italic>T</i>\u0000<sub>cr</sub>\u0000. The spontaneous magnetization \u0000<italic>M</i>\u0000<sub>S</sub>\u0000(\u0000<italic>T</i>\u0000), which was deduced by extrapolation to zero-field from the field-linear regime up to 2 T, shows an inverse variation with \u0000<italic>T</i>\u0000 and a shape change when crossing \u0000<italic>T</i>\u0000<sub>N</sub>\u0000 and \u0000<italic>T</i>\u0000<sub>2</sub>\u0000. These features, which are taken as evidence for an additional weak ferromagnetic-like component that survives above \u0000<italic>T</i>\u0000<sub>N</sub>\u0000, result from the significant role of the Pr-Cu(2) magnetic coupling.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"15 ","pages":"1-5"},"PeriodicalIF":1.2,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139950929","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 : 2023-12-18DOI: 10.1109/LMAG.2023.3344026
Oksana Koplak;Federico Maspero;Alejandro Plaza;Andrea Del Giacco;Maria Cocconcelli;Riccardo Bertacco
Thick SmCo films of 500 nm thickness were deposited by radio frequency sputtering in W/SmCo/W structures on a Si substrate. After annealing at 650–750 °C, the as-grown soft amorphous structure transforms into a mixture of crystalline Sm 2 Co 17 and SmCo 5 hard magnetic phases. Annealing at 650 °C leads to film crystallization with an average grain size of 64 nm, coercivity of 0.5 T, and remanence magnetization of about 0.5 T for a maximum applied field of 2 T. The remanence magnetization decreases by 20% upon annealing at 750 °C, whereas the average crystalline size and coercivity increase up to 73 nm and 1.1 T, respectively. Series of the first-order reversal curves recorded in the samples that were annealed at 650 °C and 750 °C demonstrate redistribution of the switching fields between the softer (Sm 2 Co 17) and harder (SmCo 5 ) phases, depending on the strength of interphase interaction. Overall, the higher remanence and sizable coercivity of films annealed at 650 °C make them good candidates for the fabrication of micromagnets to be integrated in microelectromechanical systems.
{"title":"Microstructure Evolution and First-Order Reversal Curve Analysis of the Interphase Coupling in SmCo Thick Film","authors":"Oksana Koplak;Federico Maspero;Alejandro Plaza;Andrea Del Giacco;Maria Cocconcelli;Riccardo Bertacco","doi":"10.1109/LMAG.2023.3344026","DOIUrl":"https://doi.org/10.1109/LMAG.2023.3344026","url":null,"abstract":"Thick SmCo films of 500 nm thickness were deposited by radio frequency sputtering in W/SmCo/W structures on a Si substrate. After annealing at 650–750 °C, the as-grown soft amorphous structure transforms into a mixture of crystalline Sm\u0000<sub>2</sub>\u0000Co\u0000<sub>17</sub>\u0000 and SmCo\u0000<sub>5</sub>\u0000 hard magnetic phases. Annealing at 650 °C leads to film crystallization with an average grain size of 64 nm, coercivity of 0.5 T, and remanence magnetization of about 0.5 T for a maximum applied field of 2 T. The remanence magnetization decreases by 20% upon annealing at 750 °C, whereas the average crystalline size and coercivity increase up to 73 nm and 1.1 T, respectively. Series of the first-order reversal curves recorded in the samples that were annealed at 650 °C and 750 °C demonstrate redistribution of the switching fields between the softer (Sm\u0000<sub>2</sub>\u0000Co\u0000<sub>17)</sub>\u0000 and harder (SmCo\u0000<sub>5</sub>\u0000) phases, depending on the strength of interphase interaction. Overall, the higher remanence and sizable coercivity of films annealed at 650 °C make them good candidates for the fabrication of micromagnets to be integrated in microelectromechanical systems.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"14 ","pages":"1-5"},"PeriodicalIF":1.2,"publicationDate":"2023-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139654699","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 : 2023-12-06DOI: 10.1109/LMAG.2023.3340122
Simon Häuser;Matthias R. Schweizer;Sascha Keller;Andres Conca;Moritz Hofherr;Evangelos Papaioannou;Benjamin Stadtmüller;Burkard Hillebrands;Martin Aeschlimann;Mathias Weiler
We present a study of the damping and spin pumping properties of CoFeB/X/Pt systems with $rm X=Al,Cr$ , and $rm Ta$ . We show that the total damping of the CoFeB/Pt systems is strongly reduced when an interlayer is introduced independently of the material. Using a model that considers spin relaxation, we identify the origin of this contribution in the magnetically polarized Pt formed by the magnetic proximity effect (MPE), which is suppressed by the introduction of the interlayer. The induced ferromagnetic order in the Pt layer is confirmed by element-sensitive transverse magneto-optical Kerr spectroscopy at the M $_{2,3}$ and N $_{7}$ absorption edges. We discuss the impact of the MPE on parameter extraction in the spin transport model.
{"title":"Spin Transport and Magnetic Proximity Effect in CoFeB/Normal Metal/Pt Trilayers","authors":"Simon Häuser;Matthias R. Schweizer;Sascha Keller;Andres Conca;Moritz Hofherr;Evangelos Papaioannou;Benjamin Stadtmüller;Burkard Hillebrands;Martin Aeschlimann;Mathias Weiler","doi":"10.1109/LMAG.2023.3340122","DOIUrl":"10.1109/LMAG.2023.3340122","url":null,"abstract":"We present a study of the damping and spin pumping properties of CoFeB/X/Pt systems with \u0000<inline-formula><tex-math>$rm X=Al,Cr$</tex-math></inline-formula>\u0000, and \u0000<inline-formula><tex-math>$rm Ta$</tex-math></inline-formula>\u0000. We show that the total damping of the CoFeB/Pt systems is strongly reduced when an interlayer is introduced independently of the material. Using a model that considers spin relaxation, we identify the origin of this contribution in the magnetically polarized Pt formed by the magnetic proximity effect (MPE), which is suppressed by the introduction of the interlayer. The induced ferromagnetic order in the Pt layer is confirmed by element-sensitive transverse magneto-optical Kerr spectroscopy at the M\u0000<inline-formula><tex-math>$_{2,3}$</tex-math></inline-formula>\u0000 and N\u0000<inline-formula><tex-math>$_{7}$</tex-math></inline-formula>\u0000 absorption edges. We discuss the impact of the MPE on parameter extraction in the spin transport model.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"14 ","pages":"1-5"},"PeriodicalIF":1.2,"publicationDate":"2023-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139369413","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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