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Orbital torque switching in perpendicularly magnetized materials

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arXiv

arXiv 2024年

作者： Yang, Yuhe Wang, Ping Chen, Jiali Zhang, Delin Pan, Chang Hu, Shuai Wang, Ting Yue, Wensi Chen, Cheng Jiang, Wei Zhu, Lujun Qiu, Xuepeng Yao, Yugui Li, Yue Wang, Wenhong Jiang, Yong School of Material Science and Engineering Tiangong University Tianjin300387 China Institute of Quantum Materials and Devices School of Electronic and Information Engineering Tiangong University Tianjin300387 China School of Physics Beijing Institute of Technology Beijing100081 China Beijing Key Lab of Nanophotonics & Ultrafine Optoelectronic Systems School of Physics Beijing Institute of Technology Beijing100081 China Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology School of Physics Science and Engineering Tongji University Shanghai200092 China School of Physics and Information Technology Shaanxi Normal University Xi’an710062 China School of Physical Science & Technology Tiangong University Tianjin300387 China Cangzhou Institute of Tiangong University Cangzhou061000 China

The orbital Hall effect in light materials has attracted considerable attention for developing novel orbitronic devices. Here we investigate the orbital torque efficiency and demonstrate the switching of the perpendicularly magnetized materials through the orbital Hall material (OHM), i.e., Zirconium (Zr). The orbital torque efficiency of approximately 0.78 is achieved in the Zr OHM with the perpendicularly magnetized [Co/Pt]3 sample, which significantly surpasses that of the perpendicularly magnetized CoFeB/Gd/CoFeB sample (approximately 0.04). Such notable difference is attributed to the different spin-orbit correlation strength between the [Co/Pt]3 sample and the CoFeB/Gd/CoFeB sample, which has been confirmed through the theoretical calculations. Furthermore, the full magnetization switching of the [Co/Pt]3 sample with a switching current density of approximately 2.6×106 A/cm2 has been realized through Zr, which even outperforms that of the W spin Hall material. Our finding provides a guideline to understand orbital torque efficiency and paves the way to develop energy-efficient orbitronic devices. Copyright © 2024, The Authors. All rights reserved.

关键词： Torque

Experimental Study on the Effect of Injection Pressure Ratio on the Propagation Characteristics of Hydrogen Rotating Detonation Wave

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SSRN 2022年

作者： Bai, Qiaodong Wu, Minxuan Han, Jiaxiang Zhang, Shijian Cui, Shengnan Chen, Hao Weng, Chunsheng National Key Lab of Transient Physics Nanjing University of Science and Technology Nanjing210094 China

To study the effect of the injection pressure ratio on the propagation characteristics of a rotating detonation wave (RDW) and the working range of a continuous rotating detonation engine (CRDE), experiments were conducted under different injection pressure ratios and air mass flow rates with hydrogen as the fuel and air as the oxidant. The results show that a CRDE can be detonated successfully when the injection pressure ratio ranges from 0.51 to 2.03, an RDW can propagate stably when the injection pressure ratio ranges from 0.67 to 1.7, and RDW propagation is unstable in other ranges. When the injection pressure ratio ranges from 2.08 to 3.09, the hydrogen injection pressure is less than 2 bar, and an RDW cannot be formed in the rotating detonation combustor. With an increase in the air mass flow rate, the range of the injection pressure ratio increases when the CRDE operates stably. In addition, the RDW propagation velocity first increases and then decreases with an increase in the injection pressure ratio. When the equivalent ratio is 1.2, the maximum RDW propagation velocity appears near an injection pressure ratio of 1.04. The most efficient performance of a CRDE can be achieved under these working conditions, and the RDW propagation velocity ranges from 1542 to 1621 m/s. When the air injection pressure is 3.6 bar, the rotation direction of the RDW changes during the propagation process. © 2022, The Authors. All rights reserved.

关键词： Detonation

S Doping Induced Phase Transition of CoMoO4 and Decorated on KCu7S4 for High Specific Capacitance Supercapacitor Electrode Material

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SSRN 2024年

作者： Yang, Rui Guo, Donglin Huang, Xian Yang, Kuan Yin, Huiqun Zhang, Kaiyou Qin, Aimiao Dai, Shuge Key Lab New Processing Technology for Non-ferrous Metals & Materials Ministry of Education Guangxi Key Laboratory of Optical and Electronic Materials and Devices College of Materials Science and Engineering Guilin University of Technology Guilin541004 China Key Laboratory of Material Physics of Ministry of Education School of Physics and Microelectronics Zhengzhou University Zhengzhou450052 China College of Metallurgy and Materials Engineering Chongqing University of Science and Technology Chongqing401331 China College of Physical Sciences and Technology Hebei University Baoding071002 China

Due to the importance of electrode materials for supercapacitors, modified transition metal compounds are better suited to their needs. Compounding and ion doping are two effective modification pathways to optimize the structure of electrode materials and enhance the ion migration kinetics, and thus improve the electrochemical performance of transition metal compounds. In this paper, KCu7S4@S-CoMoO4 (S doping) was prepared by a two-step hydrothermal method. The S doping would cause the phase transition of CoMoO4 and enhance crystallinity. Additionally, the possible substituted oxygen position of S atom was simulated by density functional theory (DFT). Electrochemical characterization showed that the specific capacitance of KCu7S4@S-CoMoO4 prepared under optimal condition was as high as 2866.77 F/g at a current density of 0.5 A/g. The assembled KCu7S4@SCoMoO4//AC hybrid supercapacitor exhibits the maximum energy density of 132.71 Wh/kg in liquid system condition and the specific capacitance maintained 80.9% of the initial capacitance after 3500 charge/discharge cycles. This work provides ideas for designing materials with high electrochemical performance. © 2024, The Authors. All rights reserved.

关键词： Supercapacitor

Towards Quantifying (Meta-)Stability of Multi-Principal Element Alloys: From Configurational Entropy to Characteristic Temperatures

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SSRN 2024年

作者： Zhang, Yanhui Dong, Lisheng Wang, Li-Min Liu, Ri-Ping Sanvito, Stefano State Key Lab of Metastable Materials Science and Technology College of Materials Science and Engineering Yanshan University Hebei Qinhuangdao066004 China School of Physics CRANN Institute Trinity College Dublin 2 Dublin Ireland

Understanding the metastability of multi-principal-element alloys (MPEAs) is crucial for their design and applications, but it remains an elusive task. Entropy descriptors alone are often insufficient in determining the relative stability of MPEAs, since rarely single-phase alloys can compete with their metastable counterparts and most engineered compositions form metastable rather than stable single phases. Here we introduce two characteristic temperatures, derived from the temperature dependence of the configurational entropy, which effectively act as metastability indicators. These can be further combined in a dimensionless quantity, Td0, named configuration-temperature-offshoot descriptor, which enables us to rank alloys according to their compositional and structural metastability across a broad composition range. In particular, we are able to map equiatomic and non-equiatomic alloys, and even regions covered by conventional alloys. Our proposed descriptors are validated against a large body of experimental results and compared to other (meta-)stability descriptors. Furthermore, they allow us to revise the alloys classification scheme into high-entropy, medium-entropy and low-entropy. Our work sheds new light into the thermodynamic origin of alloying metastability, it provides a potential tool to correlate metastability thermodynamics and kinetics, and ultimately may help in alloys design and discovery. © 2024, The Authors. All rights reserved.

关键词： Machine learning

A Complex Hermitian Positive Definite Manifold Embedding Transformer Network for Time-Varying Direction of Arrival Tracking

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IEEE Transactions on Cognitive Communications and Networking 2025年

作者： Teng, Liping Wang, Qing Wang, Yanhui Guo, Qinghua Li, Wanqing Tianjin University School of Electrical and Information Engineering Tianjin300072 China Nantong University School of Information Science and Technology Nantong226019 China Science and Technology on Space Physics Laboratory Beijing100076 China University of Wollongong School of Electrical Computer and Telecommunications Engineering WollongongNSW2522 Australia University of Wollongong Advanced Multimedia Research Lab WollongongNSW2522 Australia

In this work, we address the challenge of stable and robust time-varying direction-of-arrival (DOA) tracking, where both the DOA trajectory and the number of sources change over time across different scenarios. We formulate the problem as a multi-label classification task and propose a novel solution leveraging Riemannian manifold geometry and advanced neural networks for sequential data processing. Specifically, we introduce the Complex Hermitian Positive Definite embedding Transformer (C-HPD-T) network, which learns statistical representations of covariance matrices. The C-HPD-T consists of an HPD module and a Transformer module. The HPD module learns an appropriate statistical representation and the complex Transformer module models the data temporally. In particular, in the C-HPD-T network, we build a complex singular value decomposition (SVD) module to ensure that complex structure is preserved during the calculation of each layer. Meanwhile, we design a Transformer-based sequential network to capture the temporal relationship of signals and for the time-varying DOAs. Through training the network with varying numbers of moving targets featuring diverse motion trajectories, the network demonstrates excellent performance and robustness against array imperfections. Extensive simulation results demonstrate its superior performance gains compared to existing methods. © 2015 IEEE.

关键词： Covariance matrix

Roll-to-Roll Prelithiation of Li-Ion Batteries Anodes Using Ultrathin Lithium Strips

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SSRN 2024年

作者： Yi, Ruowei Hu, Shoulei Zheng, Lei Li, Yifan Luo, Wenting Zhang, Haiyang Ge, Jun Shen, Yanbin Chen, Liwei i-Lab CAS Center for Excellence in Nanoscience Suzhou Institute of Nano-Tech and Nano-Bionics Chinese Academy of Science Suzhou215123 China Nano Science and Technology Institute University of Science and Technology of China Suzhou215123 China School of Nano-Tech and Nano-Bionics University of Science and Technology of China Suzhou215123 China Vacuum Interconnected Nanotech Workstation Suzhou Institute of Nano-Tech and Nano-Bionics Chinese Academy of Sciences Suzhou215123 China In-situ Center for Physical Science School of Chemistry and Chemical Engineering Shanghai Jiaotong University Shanghai200240 China

The irreversible formation of solid electrolyte interphase (SEI) reduces lithium-ion batteries' capacity and energy density (LIBs), prompting the prelithiation strategies to compensate for the Li loss. However, the accuracy of the prelithiation degree and the SEI formation under prelithiation conditions remain key issues, especially for practical industrial production. Herein, we demonstrate that roll-to-roll prelithiation of graphite anodes can be done using ultrathin lithium strips (6-μm-thick), and the prelithiation degree can be precisely tuned by the topological distribution. More importantly, the formation of SEI during the prelithiation process and its influence on the long-term cycling performance of the prelithiated LiFePO4 || graphite pouch cells was revealed. Afterward, the prelithiated pouch LiFePO4 || graphite cell at the optimized conditions exhibits the upgraded energy density after even 1200 cycles. This study shall provide an industrial-scale prelithiation technique for high-energy-density LIBs and a pioneering systematic investigation of SEI chemistry during prelithiation. © 2024, The Authors. All rights reserved.

关键词： Lithium-ion batteries

Laser Rapid Scanning Strategy for Bitmaps Via Image Segmentation Utilizing Grey Wolf Optimizer

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SSRN 2023年

作者： Zhang, Tian Rong, Youmin Liu, Xiufeng Cao, Siyang Liang, Yufeng Wu, Congyi Zhang, Guojun Huang, Yu State Key Lab of Digital Manufacturing Equipment and Technology Huazhong University of Science and Technology Wuhan China School of Mechanical Science and Engineering Huazhong University of Science and Technology Wuhan China School of Physics and Electromechanical Engineering Hubei University of Education Wuhan China HGlaser Engineering Co. Ltd. Wuhan China

This study introduces a novel laser scanning processing methodology for bitmap aimed at reducing time losses arising from multiple galvanometer scanning cycles. The Multi-threshold Otsu method is employed and resolved using the gray wolf optimizer to effectively partition the target image into discernible background and target regions. To accommodate the resolved threshold distribution, four mapping functions with distinct growth trends are optimally selected and employed to modulate pixel gray values within specific regions into varying scanning input powers. An experimental investigation was conducted utilizing a galvanometer scanner and a set of sample images. Comparative analysis of image segmentation outcomes across multiple methodologies highlights the Gray Wolf optimizer's propensity for yielding the most robust segmentation results and solution stability. Coupled with the power mapping function, this new method exhibits notable adaptability to diverse graphical representations. Ultimately, the scanning process duration is reduced by as much as 89% when contrasted with traditional point carving and layer-by-layer scanning. This discovery signifies that the novel strategy holds significant promise for enhancing productivity in laser processing applications. © 2023, The Authors. All rights reserved.

关键词： Image segmentation

Enhanced broadband Cherenkov second-harmonic generation in nonlinear photonic crystals with a spatial chirped pulse

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Physical Review A 2024年第5期109卷 053513-053513页

作者： Bufan Jin Xuemei Wu Weimin Shen Zhi Hong Hang School of Physical Science and Technology and Collaborative Innovation Center of Suzhou Nano Science and Technology Soochow University Suzhou 215006 China Institute for Advanced Study Soochow University Suzhou 215006 China Jiangsu Key Laboratory of Frontier Material Physics and Devices Suzhou 215006 China Key Lab of Modern Optical Technologies of Education Ministry of China School of Optoelectronic Science and Engineering Soochow University Suzhou 215006 China Key Lab of Advanced Optical Manufacturing Technologies of Jiangsu Province School of Optoelectronic Science and Engineering Soochow University Suzhou 215006 China

In this work, we theoretically study the role of the spatial chirped pulse in the Cherenkov second-harmonic generation in one-dimensional nonlinear photonic crystals. We show that the spatial chirped input with narrower spectral peaks but wider angular distribution can be used to cancel the natural dispersion of crystals, fitting the phase-matching condition at wider emission angles. Contrary to popular belief, the phase-matching bandwidth can remain almost unchanged with the growth of interaction length, leading to a substantial increase in the signal strength and bandwidth under long interaction. The improvement ratio of the signal can be as high as needed, if the beam waist and the interaction length are large enough.

关键词： Nonlinear optics Phononic crystals Optical second-harmonic generation

Robust moiré flatbands within a broad band-offset range

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Advanced Photonics Nexus 2023年第6期2卷 7-13页

作者： Peilong Hong Yi Liang Zhigang Chen Guoquan Zhang University of Electronic Science and Technology of China School of Optoelectronic Science and EngineeringChengduChina Anqing Normal University School of Mathematics and PhysicsAnqingChina Nankai University TEDA Applied Physics InstituteSchool of PhysicsThe MOE Key Laboratory of Weak-Light Nonlinear PhotonicsTianjinChina Guangxi University School of Physical Science and TechnologyCenter on Nanoenergy ResearchGuangxi Key Lab for Relativistic AstrophysicsNanningChina

Photonic analogs of the moirésuperlattices mediated by interlayer electromagnetic coupling are expected to give rise to rich phenomena,such as nontrivial flatband ***,we propose and demonstrate a scheme to tune the flatbands in a bilayer moirésuperlattice by employing a band *** band offset is changed by fixing the bands of one slab while shifting those of the other slab,which is accomplished by modifying the thickness of the latter *** results show that the band-offset tuning not only makes some flatbands emerge and disappear but also leads to two sets of flatbands that are robustly formed even with the change of band offset over a broad *** robust flatbands form either at the AA-stack site or at the AB-stack site,and as a result,a single-cell superlattice can support a pair of high-quality localized modes with tunable ***,we develop a diagrammatic model to provide an intuitive insight into the formation of the robust *** work demonstrates a simple yet efficient way to design and control complex moiréflatbands,providing new opportunities to utilize photonic moirésuperlattices for advanced light–matter interaction,including lasing and nonlinear harmonic generation.

关键词： moirésuperlattice robust flatbands doubly resonant superlattice diagrammatic model