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}
Pub Date : 2023-11-20DOI: 10.1109/LMAG.2023.3334670
Victoria Martinez;Ezio Iacocca
The shape of nanoislands gives rise to a demagnetizing field that is primarily responsible for the orientation of the magnetization along an axis. In the context of magnetization dynamics, the demagnetization (demag) field also determines the resonant frequencies captured by Kittel's equations. Analytically, we require demag factors that can be obtained exactly for a few geometries, including ellipsoids and prisms. However, analytical expressions are not available for other shapes, limiting the use of Kittel's equation as a predictive model. Here, we present a method to obtain the demag factors from micromagnetic simulations with good accuracy. Similar to other experiments, ferromagnetic resonance was obtained, but we use orthogonal field conditions to fit Kittel's equation unambiguously and obtain the demag factors with good accuracy. This method will be useful to determine demag factors under the ellipsoidal approximation for stadium-shaped nanoislands used in artificial spin ices and thus lead to a better prediction in their ferromagnetic resonance and band structures.
{"title":"A Numerical Method to Determine Demagnetization Factors of Stadium-Shaped Nanoislands for Artificial Spin Ices","authors":"Victoria Martinez;Ezio Iacocca","doi":"10.1109/LMAG.2023.3334670","DOIUrl":"https://doi.org/10.1109/LMAG.2023.3334670","url":null,"abstract":"The shape of nanoislands gives rise to a demagnetizing field that is primarily responsible for the orientation of the magnetization along an axis. In the context of magnetization dynamics, the demagnetization (demag) field also determines the resonant frequencies captured by Kittel's equations. Analytically, we require demag factors that can be obtained exactly for a few geometries, including ellipsoids and prisms. However, analytical expressions are not available for other shapes, limiting the use of Kittel's equation as a predictive model. Here, we present a method to obtain the demag factors from micromagnetic simulations with good accuracy. Similar to other experiments, ferromagnetic resonance was obtained, but we use orthogonal field conditions to fit Kittel's equation unambiguously and obtain the demag factors with good accuracy. This method will be useful to determine demag factors under the ellipsoidal approximation for stadium-shaped nanoislands used in artificial spin ices and thus lead to a better prediction in their ferromagnetic resonance and band structures.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"14 ","pages":"1-4"},"PeriodicalIF":1.2,"publicationDate":"2023-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138822044","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 : 2023-10-13DOI: 10.1109/LMAG.2023.3324517
Lei Wang;Duan Nie;Liye Cheng;Hongyue Wang
This letter presents a high-sensitivity composite probe capable of simultaneously measuring electric- and magnetic-field components. The composite probe contains a U-shaped loop, two parasitic long loops, and a pair of strip lines as a transmission part. First, the U-shaped loop is designed to test both electric and magnetic fields. Second, two parasitic long loops are placed at both sides of the U-shaped loop to increase the sensitivity. Third, to characterize and calibrate the probe, a standard microstrip line is manufactured and used. Finally, the developed probe is printed and tested to prove the feasibility of the design. The tested results indicate that the probe can not only simultaneously test electric and magnetic fields, but also have a wider working bandwidth and higher sensitivity.
这封信介绍了一种能够同时测量电场和磁场分量的高灵敏度复合探针。该复合探头包含一个 U 形环、两个寄生长环和一对作为传输部分的带状线。首先，U 型环设计用于测试电场和磁场。其次，在 U 型环的两侧设置了两个寄生长环，以提高灵敏度。第三，为了鉴定和校准探头，制造并使用了标准微带线。最后，对开发的探头进行打印和测试，以证明设计的可行性。测试结果表明，该探针不仅可以同时测试电场和磁场，而且具有更宽的工作带宽和更高的灵敏度。
{"title":"A High-Sensitivity Composite Probe Capable of Simultaneously Measuring Electric- and Magnetic-Field Components","authors":"Lei Wang;Duan Nie;Liye Cheng;Hongyue Wang","doi":"10.1109/LMAG.2023.3324517","DOIUrl":"10.1109/LMAG.2023.3324517","url":null,"abstract":"This letter presents a high-sensitivity composite probe capable of simultaneously measuring electric- and magnetic-field components. The composite probe contains a U-shaped loop, two parasitic long loops, and a pair of strip lines as a transmission part. First, the U-shaped loop is designed to test both electric and magnetic fields. Second, two parasitic long loops are placed at both sides of the U-shaped loop to increase the sensitivity. Third, to characterize and calibrate the probe, a standard microstrip line is manufactured and used. Finally, the developed probe is printed and tested to prove the feasibility of the design. The tested results indicate that the probe can not only simultaneously test electric and magnetic fields, but also have a wider working bandwidth and higher sensitivity.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"14 ","pages":"1-5"},"PeriodicalIF":1.2,"publicationDate":"2023-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136306060","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 summarizes the recent development of magnetic materials search using artificial intelligence (AI) and machine learning (ML) and briefly introduces ML and AI approaches to materials discovery. The authors offer a flowchart to aid the selection of relevant approaches for their material search. This letter also covers the authors' recent research activities in magnetism and quantum materials, including topological materials, Heusler alloys, interfaces, and permanent magnets. This overview is based on a recent symposium at IEEE Intermag 2023.
{"title":"Materials Informatics for the Development and Discovery of Future Magnetic Materials","authors":"Ryotaro Okabe;Mingda Li;Yuma Iwasaki;Nicolas Regnault;Claudia Felser;Masafumi Shirai;Alexander Kovacs;Thomas Schrefl;Atsufumi Hirohata","doi":"10.1109/LMAG.2023.3320888","DOIUrl":"10.1109/LMAG.2023.3320888","url":null,"abstract":"This letter summarizes the recent development of magnetic materials search using artificial intelligence (AI) and machine learning (ML) and briefly introduces ML and AI approaches to materials discovery. The authors offer a flowchart to aid the selection of relevant approaches for their material search. This letter also covers the authors' recent research activities in magnetism and quantum materials, including topological materials, Heusler alloys, interfaces, and permanent magnets. This overview is based on a recent symposium at IEEE Intermag 2023.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"14 ","pages":"1-5"},"PeriodicalIF":1.2,"publicationDate":"2023-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10268090","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135839038","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 has been a strong demand for soft magnetic films suitable for high-frequency micromagnetic devices as power electronics circuits to operate at higher frequencies. Specifically, there is a need for magnetic thin films with ferromagnetic resonance frequencies ( f r ) in the range of several gigahertz. Nanogranular CoZrO thin films have emerged as promising candidates due to their high f r and high electrical resistivity. We fabricated CoZrO thin films using facing targets reactive sputtering with oxygen as the reactive gas. As the oxygen partial pressure ratio ( P O2 ) was gradually increased up to 0.8%, clear uniaxial magnetic anisotropy appeared, leading to improved soft magnetic properties. At a P O2 of 0.8%, the film exhibited the most superior soft magnetic properties. With further increase in P O2 , magnetic loops implying a stripe magnetic-domain structure were obtained. In this P O2 range, phase separation was observed, along with a sharp increase in electrical resistivity. f r of the CoZrO film formed at P O2 = 0.8% was determined to be 3.2 GHz from high-frequency permeability measurement. We have confirmed the effectiveness of facing targets’ reactive sputtering in preparing CoZrO films with excellent soft magnetic properties.
{"title":"Fabrication and Characterization CoZrO Films Deposited by Facing Targets Reactive Sputtering for Micromagnetic Inductors","authors":"Honami Nitta;Yota Takamura;Tadayuki Kaneko;Shigeki Nakagawa","doi":"10.1109/LMAG.2023.3320495","DOIUrl":"10.1109/LMAG.2023.3320495","url":null,"abstract":"In recent years, there has been a strong demand for soft magnetic films suitable for high-frequency micromagnetic devices as power electronics circuits to operate at higher frequencies. Specifically, there is a need for magnetic thin films with ferromagnetic resonance frequencies (\u0000<italic>f</i>\u0000<sub>r</sub>\u0000) in the range of several gigahertz. Nanogranular CoZrO thin films have emerged as promising candidates due to their high \u0000<italic>f</i>\u0000<sub>r</sub>\u0000 and high electrical resistivity. We fabricated CoZrO thin films using facing targets reactive sputtering with oxygen as the reactive gas. As the oxygen partial pressure ratio (\u0000<italic>P</i>\u0000<sub>O2</sub>\u0000) was gradually increased up to 0.8%, clear uniaxial magnetic anisotropy appeared, leading to improved soft magnetic properties. At a \u0000<italic>P</i>\u0000<sub>O2</sub>\u0000 of 0.8%, the film exhibited the most superior soft magnetic properties. With further increase in \u0000<italic>P</i>\u0000<sub>O2</sub>\u0000, magnetic loops implying a stripe magnetic-domain structure were obtained. In this \u0000<italic>P</i>\u0000<sub>O2</sub>\u0000 range, phase separation was observed, along with a sharp increase in electrical resistivity. \u0000<italic>f</i>\u0000<sub>r</sub>\u0000 of the CoZrO film formed at \u0000<italic>P</i>\u0000<sub>O2</sub>\u0000 = 0.8% was determined to be 3.2 GHz from high-frequency permeability measurement. We have confirmed the effectiveness of facing targets’ reactive sputtering in preparing CoZrO films with excellent soft magnetic properties.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"14 ","pages":"1-5"},"PeriodicalIF":1.2,"publicationDate":"2023-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135838519","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 : 2023-09-27DOI: 10.1109/LMAG.2023.3319992
Rahnuma Rahman;Supriyo Bandyopadhyay
Probabilistic computing with binary stochastic neurons (BSNs) implemented with low-barrier magnets (LBMs) or zero-energy barrier nanoscale ferromagnets possessing in-plane magnetic anisotropy has emerged as an efficient paradigm for solving computationally hard problems. The fluctuating magnetization of an LBM at room temperature encodes a p-bit, which is the building block of a BSN. Its drawback, however, is that the dynamics of common (transition metal) ferromagnets are relatively slow, and, hence, the number of uncorrelated p-bits that can be generated per second—the so-called “flips per second” ( fps )—is insufficient, leading to slow computational speed in autonomous coprocessing with p-computers. Here, we show that a simple way to increase fps in LBMs is to replace commonly used ferromagnets (e.g., Co, Fe, and Ni), which have large saturation magnetization Ms , with a dilute magnetic semiconductor, such as GaMnAs with much smaller saturation magnetization. The smaller Ms reduces any residual energy barrier within an LBM and increases the fps significantly. It also offers other benefits, such as reduced dipole coupling between neighbors, resulting in larger density of uncorrelated p-bits for more processing power, and reduced device-to-device variation. All this provides a way to realize the hardware acceleration and energy efficiency promise of p-computers.
{"title":"Increasing Flips per Second and Speed of p-Computers by Using Dilute Magnetic Semiconductors","authors":"Rahnuma Rahman;Supriyo Bandyopadhyay","doi":"10.1109/LMAG.2023.3319992","DOIUrl":"https://doi.org/10.1109/LMAG.2023.3319992","url":null,"abstract":"Probabilistic computing with binary stochastic neurons (BSNs) implemented with low-barrier magnets (LBMs) or zero-energy barrier nanoscale ferromagnets possessing in-plane magnetic anisotropy has emerged as an efficient paradigm for solving computationally hard problems. The fluctuating magnetization of an LBM at room temperature encodes a p-bit, which is the building block of a BSN. Its drawback, however, is that the dynamics of common (transition metal) ferromagnets are relatively slow, and, hence, the number of uncorrelated p-bits that can be generated per second—the so-called “flips per second” (\u0000<italic>fps</i>\u0000)—is insufficient, leading to slow computational speed in autonomous coprocessing with p-computers. Here, we show that a simple way to increase \u0000<italic>fps</i>\u0000 in LBMs is to replace commonly used ferromagnets (e.g., Co, Fe, and Ni), which have large saturation magnetization \u0000<italic>M<sub>s</sub></i>\u0000, with a dilute magnetic semiconductor, such as GaMnAs with much smaller saturation magnetization. The smaller \u0000<italic>M<sub>s</sub></i>\u0000 reduces any residual energy barrier within an LBM and increases the \u0000<italic>fps</i>\u0000 significantly. It also offers other benefits, such as reduced dipole coupling between neighbors, resulting in larger density of uncorrelated p-bits for more processing power, and reduced device-to-device variation. All this provides a way to realize the hardware acceleration and energy efficiency promise of p-computers.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"14 ","pages":"1-4"},"PeriodicalIF":1.2,"publicationDate":"2023-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67763009","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 : 2023-09-26DOI: 10.1109/LMAG.2023.3319289
Guannan Wei;Rajasree Das;Daniel Lordan;Marek Lorenc;Barry Clark;David P. F. Hurley;Mike Hayes;Cian O'Mathuna;Ranajit Sai;Paul McCloskey
Soft magnetic properties of thin films for use as a core material are critical for the realization of future miniaturized electromagnetic devices operating at frequencies of tens or hundreds of megahertz. Laminated stacks consisting of alternate thin layers of magnetic material and dielectric material are widely used to suppress eddy current losses that dominate, especially at a higher frequency of operation. Thus, identifying a suitable dielectric layer, its optimum thickness, and the understanding of its effect on the performance of the laminated core is important. In this letter, six different CoZrTaB (CZTB) laminated cores are reported, featuring a variety of dielectric materials (AlN, SiN, Al 2 O 3 , and oxide CZTB) and/or dielectric thickness (5, 15, and 50 nm). This study shows that stacks with different dielectric materials have a varied residual stress that plays an important role in inducing magnetic anisotropy, thus affecting the permeability. CZTB stacks with oxide CZTB dielectric show the best combination of high permeability, low coercivity, and low losses at high frequency.
{"title":"Investigation of the Soft-Magnetic Properties of CoZrTaB Laminated Cores by Dielectric Layer Tuning","authors":"Guannan Wei;Rajasree Das;Daniel Lordan;Marek Lorenc;Barry Clark;David P. F. Hurley;Mike Hayes;Cian O'Mathuna;Ranajit Sai;Paul McCloskey","doi":"10.1109/LMAG.2023.3319289","DOIUrl":"https://doi.org/10.1109/LMAG.2023.3319289","url":null,"abstract":"Soft magnetic properties of thin films for use as a core material are critical for the realization of future miniaturized electromagnetic devices operating at frequencies of tens or hundreds of megahertz. Laminated stacks consisting of alternate thin layers of magnetic material and dielectric material are widely used to suppress eddy current losses that dominate, especially at a higher frequency of operation. Thus, identifying a suitable dielectric layer, its optimum thickness, and the understanding of its effect on the performance of the laminated core is important. In this letter, six different CoZrTaB (CZTB) laminated cores are reported, featuring a variety of dielectric materials (AlN, SiN, Al\u0000<sub>2</sub>\u0000O\u0000<sub>3</sub>\u0000, and oxide CZTB) and/or dielectric thickness (5, 15, and 50 nm). This study shows that stacks with different dielectric materials have a varied residual stress that plays an important role in inducing magnetic anisotropy, thus affecting the permeability. CZTB stacks with oxide CZTB dielectric show the best combination of high permeability, low coercivity, and low losses at high frequency.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"14 ","pages":"1-5"},"PeriodicalIF":1.2,"publicationDate":"2023-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67763016","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}
Magnetic materials with low magnetic loss are required to realize both a high-frequency support and a miniaturization of radio frequency components. Hexagonal close-packed cobalt (hcp-Co) nanoparticles are considered suitable for high frequencies due to their nanoparticle morphology and high magnetocrystalline anisotropy. However, the face-centered cubic (fcc) or the ϵ phase with low magnetocrystalline anisotropy is fabricated in the synthetization of Co nanoparticles with a size of less than a few hundred nanometers. In this letter, we investigate the synthesis of Co nanoparticles by the thermolysis of dicobalt octacarbonyl at various temperatures for obtaining Co particles with a single hcp phase. Although Co nanoparticles synthesized at 453 K exhibited a mixture of hcp and fcc phases with an hcp phase ratio of 25%, Co nanoparticles almost achieved the hcp phase ratio of 100% by decreasing the thermolysis temperature to 333 K or lower. Furthermore, we evaluated the permeability spectrum of the composite with Co particles of 10 vol% dispersed in polystyrene. Although the real part of the permeability in the composite containing Co nanoparticles with the mixed phase of fcc and hcp monotonously decreased with frequency, the composite contained Co nanoparticles with a single phase with a suitable constant value up to 3 GHz for high-frequency applications.
{"title":"Synthesis of Hexagonal Close-Packed Cobalt Nanoparticles From Thermolysis of Cobalt Carbonyl","authors":"Kyohei Takahashi;Hiroshi Ito;Isao Kanada;Hiroyuki Matsumoto","doi":"10.1109/LMAG.2023.3316608","DOIUrl":"https://doi.org/10.1109/LMAG.2023.3316608","url":null,"abstract":"Magnetic materials with low magnetic loss are required to realize both a high-frequency support and a miniaturization of radio frequency components. Hexagonal close-packed cobalt (hcp-Co) nanoparticles are considered suitable for high frequencies due to their nanoparticle morphology and high magnetocrystalline anisotropy. However, the face-centered cubic (fcc) or the ϵ phase with low magnetocrystalline anisotropy is fabricated in the synthetization of Co nanoparticles with a size of less than a few hundred nanometers. In this letter, we investigate the synthesis of Co nanoparticles by the thermolysis of dicobalt octacarbonyl at various temperatures for obtaining Co particles with a single hcp phase. Although Co nanoparticles synthesized at 453 K exhibited a mixture of hcp and fcc phases with an hcp phase ratio of 25%, Co nanoparticles almost achieved the hcp phase ratio of 100% by decreasing the thermolysis temperature to 333 K or lower. Furthermore, we evaluated the permeability spectrum of the composite with Co particles of 10 vol% dispersed in polystyrene. Although the real part of the permeability in the composite containing Co nanoparticles with the mixed phase of fcc and hcp monotonously decreased with frequency, the composite contained Co nanoparticles with a single phase with a suitable constant value up to 3 GHz for high-frequency applications.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"14 ","pages":"1-4"},"PeriodicalIF":1.2,"publicationDate":"2023-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67763015","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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