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Magnetic control of heat generation in a magnetic tunnel contact with spin accumulation

Physical Review B 2022年第18期106卷 184421-184421页

作者： R. Jansen A. Spiesser S. Yuasa Research Center for Emerging Computing Technologies National Institute of Advanced Industrial Science and Technology (AIST) Tsukuba Ibaraki 305-8568 Japan

It is described how the heat generation by an electrical current in a ferromagnetic tunnel contact to a nonmagnetic material depends on the spin accumulation in the nonmagnetic electrode for both Joule and Peltier heating. This enables the control of the heating in the tunnel contact by an external applied magnetic field that induces spin precession of the spin accumulation. Thereby, a Hanle type of spin signal is imprinted in the heating power. We derive expressions for the magnitude and sign of the magnetic-field-dependent heating power for Joule and Peltier heating, and discuss the important parameters. For contacts with small resistance-area product, the spin accumulation provides the dominant contribution to the Joule heating power, which can therefore be modulated by more than a factor of 2 with a magnetic field. The described phenomenon can also produce genuine spin signals in various devices, including nonlocal lateral spin valves.

关键词： Spin accumulation Spin caloritronics Spin current Thermomagnetic effects Tunnel junctions

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Write Error Rate in Bias-Magnetic-Field-Free Voltage-Induced Switching in a Conically Magnetized Free Layer

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Physical Review Applied 2022年第3期17卷 034063-034063页

作者： R. Matsumoto H. Imamura National Institute of Advanced Industrial Science and Technology (AIST) Research Center for Emerging Computing Technologies Tsukuba Ibaraki 305-8568 Japan

Write error rate (WER) in voltage-induced magnetization switching of a conically magnetized free layer with an elliptic cylinder shape is numerically calculated on the basis of the macrospin model. Simulations using the Langevin equation show that a WER lower than the order of 10−5, which enables practical WER with a single error-correction process, is theoretically feasible at zero-bias magnetic field and room temperature. We also show that WER at a given thermal stability factor and the volume of the free layer can be reduced by adopting the free layer with the larger in-plane shape anisotropy field and a moderate cone angle at zero-bias voltage.

关键词： Magnetic anisotropy Magnetization switching Spintronics Devices for digital logic, storage & processing Ferromagnets Magnetic tunnel junctions Nanostructures Langevin equation

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Heavily Damped Precessional Switching with Very Low Write-Error Rate in Elliptical-Cylinder Magnetic Tunnel Junctions

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Physical Review Applied 2022年第5期18卷 054069-054069页

作者： R. Matsumoto S. Yuasa H. Imamura National Institute of Advanced Industrial Science and Technology (AIST) Research Center for Emerging Computing Technologies Ibaraki Tsukuba 305-8568 Japan

Voltage-induced dynamic switching in magnetic tunnel junctions (MTJs) is a writing technique for voltage-controlled magnetoresistive random access memory (VCMRAM), which is expected to be an ultimate nonvolatile memory with ultralow power consumption. In conventional dynamic switching, the width of subnanosecond write voltage pulses must be precisely controlled to achieve a sufficiently low write-error rate (WER). This very narrow tolerance of pulse width is the biggest technical difficulty in developing VCMRAM. Heavily damped precessional switching is a writing scheme for VCMRAM with a substantially high tolerance of pulse width, although the minimum WER has been much higher than that of conventional dynamic switching with an optimum pulse width. In this study, we theoretically investigate the effect of MTJ shape and the direction of the applied magnetic field on the WER of heavily damped precessional switching. The results show that the WER in elliptical-cylinder MTJs can be several orders of magnitude smaller than that in usual circular-cylinder MTJs when the external magnetic field is applied parallel to the minor axis of the ellipse. The reduction in the WER is due to the fact that the demagnetization field narrows the component of the magnetization distribution perpendicular to the plane direction immediately before the voltage is applied.

关键词： Demagnetization Magnetic anisotropy Magnetization dynamics Spin dynamics Spintronics Devices for digital logic, storage & processing Magnetic tunnel junctions Landau-Lifschitz-Gilbert equation

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Enhancing voltage-controlled magnetic anisotropy in Fe80B20/MgO/HfO2 thin films by dielectric constant modulation

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Physical Review Materials 2022年第10期6卷 104406-104406页

作者： Hiroshige Onoda Tomohiro Nozaki Shingo Tamaru Takayuki Nozaki Shinji Yuasa National Institute of Advanced Industrial Science and Technology (AIST) Research Center for Emerging Computing Technologies Tsukuba Ibaraki 305-8568 Japan

The voltage-controlled magnetic anisotropy (VCMA) effect is the basis for ultralow-power spin manipulation in spintronic devices such as voltage-controlled magnetoresistive random-access memory (VC-MRAM). A larger VCMA coefficient ξ is required to develop VC-MRAM with a higher density. Although ξ is theoretically proportional to the dielectric constant ɛr of the tunnel barrier material, this relationship has not been experimentally examined. We systematically investigated the relationship between ξ and ɛr in a Fe80B20/MgO/HfO2 structure prepared by sputtering-based deposition. We successfully controlled ɛr while maintaining perpendicular magnetic anisotropy at the Fe80B20/MgO interface. Both ɛr and ξ were observed to monotonically increase with HfO2, showing a positive correlation between ξ and ɛr. The maximum ξ reached −92 ± 4 fJ/Vm with ɛr=19.6±0.3. This result experimentally demonstrated that the VCMA effect could be enhanced by increasing ɛr.

关键词： Dielectric properties Ferromagnetism Magnetoelectric effect Materials Thin films

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QDL: Quantitative Dynamic Latency Model in Permissioned Blockchain System 22

QDL: Quantitative Dynamic Latency Model in Permissioned Bloc...

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22nd IEEE International Symposium on Parallel and Distributed Processing with Applications, ISPA 2024

作者： Wei, Jiacheng Wang, Qingmei Wang, Zheng Beihang University School of Artificial Intelligence Beijing China Beihang University Beijing Advanced Innovation Center for Future Blockchain and Privacy Computing Beijing China University of Science and Technology Beijing National Center for Materials Service Safety Beijing China Shanghai Jiao Tong University Institute of Cyber Science and Technology China Shanghai Key Laboratory of Integrated Administration Technologies for Information Security China

ISBN: (纸本)9798331509712

Latency, as a critical attribute influencing scalability and consistency in blockchain systems, has attracted significant research attention. This paper addresses the issue of latency evaluation by presenting a novel framework. We thoroughly analyze the factors affecting latency in blockchain system, including concurrency, consistency, and contention. To accurately model the correlation between latency and the quantity of nodes in permissioned blockchain setup, we introduce the Latency Regression Loss (LRL) function. By utilizing Newton's interpolation and least squares methods, we determine the hyperparameters. Subsequently, we devise the framework for the Quantitative Dynamic Latency (QDL) evaluation model, which accounts for both the growth rate and magnitude of latency. Utilizing the parameters derived from the LRL function facilitated the calculation of latency growth rate, allowing for a comprehensive evaluation of latency. Finally, we validated the accuracy of the LRL function through extensive experiments and simulated the adaptability of the QDL model in latency assessment. © 2024 IEEE.

关键词： Scalability

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Growth of InAs quantum dots on the modified GaAs surface by using in-situ multi-pulsed laser shooting 10

Growth of InAs quantum dots on the modified GaAs surface by ...

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10th Symposium on Novel Optoelectronic Detection Technology and Applications

作者： Cheng, Lingsu Geng, Biao Ren, Maoyun Peng, Chunbo Guo, Yu Shi, Zhenwu Peng, Changsi School of Optoelectronic Science and Engineering Collaborative Innovation Center of Suzhou Nano Science and Technology Soochow University Suzhou215006 China Key Lab of Advanced Optical Manufacturing Technologies of Jiangsu Province Key Lab of Modern Optical Technologies of Education Ministry of China Soochow University Suzhou215006 China Institute of Research for Applicable Computing University of Bedfordshire Park Square LutonLU1 3JU United Kingdom

ISBN: (数字)9781510688155

ISBN: (纸本)9781510688148

In this work, we subjected the GaAs substrate to in-situ irradiation by 10 laser pulses with 30 second interruption among each pulse at a temperature of 500℃ without As flux. Then the substrate was annealed at the same temperature for 5 minutes under As flux. We have respectively prepared a series of samples corresponding to different pulse energies (1mJ-8mJ). At the very low energy stage (1-2mJ), oval islands elongated along [-110] can be observed on the surface. At the medium energy stage (2-4mJ), the oval islands will become larger and meanwhile some very narrow nano grooves (elongated along [110]) will appear at the center of the island. At the high energy stage (4-8mJ), the islands will become larger and the grooves will widen into nano holes. The whole structure almost looks like a nano ring with a nano hole at the center. Then, we conducted a study of InAs quantum dot growth on these obtained nano structures. The results show all the InAs quantum dots strictly grow surrounding the oval islands or in the nano holes after the deposition of 2.2ML InAs at 500℃. So these structures can effectively serve as the preferential nucleation sites for quantum dots. © 2025 SPIE.

关键词： Molecular beam epitaxy

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Fabrication of periodic gallium droplets by in-situ laser interference based on MBE 10

Fabrication of periodic gallium droplets by in-situ laser in...

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10th Symposium on Novel Optoelectronic Detection Technology and Applications

作者： Ren, Maoyun Geng, Biao Cheng, Lingsu Guo, Yu Peng, Chunbo Shi, Zhenwu Peng, Changsi School of Optoelectronic Science and Engineering Collaborative Innovation Center of Suzhou Nano Science and Technology Soochow University Suzhou215006 China Key Lab of Advanced Optical Manufacturing Technologies of Jiangsu Province Key Lab of Modern Optical Technologies of Education Ministry of China Soochow University Suzhou215006 China Institute of Research for Applicable Computing University of Bedfordshire Park Square LutonLU1 3JU United Kingdom

ISBN: (数字)9781510688155

ISBN: (纸本)9781510688148

In this work, the GaAs substrate was in-situ irradiated by a single-pulse of two-beam laser interference at a low temperature of 40℃. We studied the irradiated surface morphology evolution with the different pulse energies of 20mJ, 40mJ, 50mJ, 60mJ, 80mJ and 100mJ which are corresponding to sample A-F. For Sample A, the irradiation yield of Ga atoms is too limited to form metallic droplets but films with a period of about 310nm due to the low pulse energy. For Sample B, periodic bands of Ga droplets appear on the bright regions while the surface on the dark regions remains very smooth. The droplet density, average width and height are 7.5×1010/cm2, 25nm and 5.1nm. For sample C to E, as the energy rises, the average width/height of Ga droplets rise from 33nm/5.9nm, 36.7nm/8.7nm to 52.1nm/15.7nm but with the decreased density from 5.8×1010/cm2, 4×1010/cm2 to 1.7×1010/cm2. Moreover, some small Ga droplets also appear in the dark regions. Finally for sample F, when the energy becomes enough high, both the dark and bright regions generate Ga droplets of a similar size and density which is equivalent to the random growth. The resulting density is 7.4×109/cm2 and the average width/height is 63.6nm/20.2nm. Obviously, our work has provided a novel approach for fabricating periodic Ga droplets directly in MBE systems with the advantages of low-cost, high-efficiency and strong controllability which must be able to find great application prospects in droplet epitaxy of all kinds of semiconductor devices based on periodic arrays of quantum structures. © 2025 SPIE.

关键词： Molecular beam epitaxy

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Higher-order Bloch sphere: geometric representation of Larmor precession of the higher-order spin states

Higher-order Bloch sphere: geometric representation of Larmo...

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2022 Conference on Lasers and Electro-Optics Pacific Rim, CLEO/PR 2022

作者： Sato, Sota Matsumoto, Toshiki Iba, Satoshi Miyamoto, Katsuhiko Omatsu, Takashige Morita, Ken Graduate School of Science and Engineering Chiba University Japan Department of Electrical and Electronic Engineering Chiba University Japan Research Center for Emerging Computing Technologies National Institute of Advanced Industrial Science and Technology Japan

We propose an analogous sphere, herein referred a higher-order Bloch sphere (HOBS), to visualize the Larmor precession of higher-order spin. Our proposed HOBS is potentially applied to advanced quantum information pro... 详细信息

关键词： Spheres

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Higher-order Bloch sphere: geometric representation of Larmor precession of the higher-order spin states

Higher-order Bloch sphere: geometric representation of Larmo...

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2022 Conference on Lasers and Electro-Optics Pacific Rim, CLEO-PR 2022

ISBN: (纸本)9798350350012

关键词：

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Probability maximization of magnetization switching by spin-orbit torques generated by a ferromagnet

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Physical Review B 2025年第9期111卷 094420-094420页

作者： Tomohiro Taniguchi Shinji Isogami Shuji Okame Katsuyuki Nakada Tomoyuki Sasaki Seiji Mitani Masamitsu Hayashi National Institute of Advanced Industrial Science and Technology (AIST) Research Center for Emerging Computing Technologies Tsukuba Ibaraki 305-8568 Japan National Institute for Materials Science Tsukuba 305-0047 Japan Advanced Products Development Center Technology & Intellectual Property HQ TDK Corporation Ichikawa Chiba 272-8558 Japan Department of Physics The University of Tokyo Tokyo 113-8654 Japan

Spin-orbit torques (SOTs) caused by spin currents generated in a ferromagnetic electrode enable a fast and deterministic magnetization switching. One SOT (y-SOT), polarized orthogonal to both electric current flowing in the electrode and easy axis of a ferromagnetic free layer, causes fast magnetization instability. The other SOT (z-SOT) points to the easy-axis direction and leads to the deterministic switching. Here, we evaluate the magnetization switching probability by these SOTs for various values of electric current density and the ratio of two SOTs from numerical simulation of the Landau-Lifshitz-Gilbert (LLG) equation. It is found that the switching probability is maximized when the electric current density is close to a critical value for the magnetization destabilization solely by the y-SOT. The origin of such a current dependence is investigated by analyzing temporal dynamics, spectra of the magnetization distribution, and a steady-state solution of the LLG equation. We reveal that the maximization of the switching probability originates due to two different switching behaviors. In the low current region, the magnetization in some trials remains near the initial state because of the weak y-SOT, and thus, the switching error occurs. The number of such trials, which represents the switching error, decreases as the electric current density increases because both y and z-SOTs prompt the switching. In the large current region, the large y-SOT immediately tilts the magnetization toward the switched direction. However, since the y-SOT prefers an in-plane magnetized state, the switching error due to a probabilistic return to the initial state after turning off the electric current density occurs. The switching error in this region tends to increase with increasing current density. As a result, the switching probability is optimized when the electric current density is close to the critical value.

关键词： Ferromagnetism

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