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Bondage number of strong product of two paths

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Frontiers of Mathematics in China 2015年第2期10卷 435-460页

作者： weisheng zhao Heping ZHANG School of Mathematics and Statistics Lanzhou University Lanzhou 730000 China

The bondage number b（G） of a graph G is the cardinality of a minimum set of edges whose removal from G results in a graph with a domination number greater than that of G. In this paper, we obtain the exact value of the bondage number of the strong product of two paths. That is, for any two positive integers ra ≥ 2 and n ≥ 2, b（Pm × Pn） = 7 - r（m） - r（n） if （r（m）,r（n）） = （1, 1） or （3,3）, 6 - r（m） - r（n） otherwise, where r（t） is a function of positive integer t, defined as r（t） = 1 if t ≡ 1 （mod 3）, r（t） = 2 if t ≡2 （mod 3）, and r（t） = 3 if t ≡0 （mod 3）.

关键词： Bondage number strong product path

Developments and Applications of Tunneling Magnetoresistance Sensors

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Tsinghua Science and Technology 2022年第3期27卷 443-454页

作者： Shaohua Yan Zitong Zhou Yaodi Yang Qunwen Leng weisheng zhao the School of Integrated Circuit Science and Engineering Beihang UniversityBeijing 100191China Beihang-Goertek Joint Microelectronics Institute Qingdao Research Institute of Beihang UniversityQingdao 266100China

Magnetic sensors based on tunneling magnetoresistance(TMR)effect exhibit high sensitivity,small size,and low power *** have gained a lot of attention and have potential applications in various *** study first introduces the development history and basic principles of TMR ***,a comprehensive description of TMR sensors linearization and Wheatstone bridge configuration is *** key performance parameters,the field sensitivity and noise mechanisms,are ***,the emerging applications of TMR sensors are discussed.

关键词： tunneling magnetoresistance(TMR)sensor linearization Wheatstone bridge configuration noise

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Perpendicular magnetic anisotropy based spintronics devices in Pt/Co stacks under different hard and flexible substrates

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Science China(Information Sciences) 2023年第2期66卷 256-266页

作者： Sylvain EIMER Houyi CHENG Jinji LI Xueying ZHANG Chao zhao weisheng zhao Hefei Innovation Research Institute Anhui High Reliability Chips Engineering LaboratoryBeihang University Fert Beijing Institute MIIT Key Laboratory of Spintronics School of Integrated Circuit Science and EngineeringBeihang University School of Physics and Quantum Information Research Center Southeast University Truth Instruments Co.Ltd. Beihang-Geortek Joint Microelectronics Institute Qingdao Research InstituteBeihang University Beijing Superstring Academy of Memory Technology

The magnetic properties in substrate/Pt/Co multilayers, such as perpendicular magnetic anisotropy(PMA), are of particular interest for spintronic devices. In particular, it is important to obtain a strong PMA on the flexible substrate in the field of wearable devices and structural health ***, the different stacks deposition and regulation conditions on the magnetic properties of the films lack systematic research. Here, we investigate the magnetic properties in Pt/Co structures with different hard and flexible substrates, layer thicknesses, and the different deposition temperatures of the buffer *** found that the coercive field and magnetodynamic behavior of the films change with these factors. Moreover, depositing the buffer layer under high temperature can effectively adjust the crystalline state of the films, thus affecting the performance of the films. After depositing the buffer layer at 800℃, our films can obtain a better crystalline state and PMA. The measurement results of the magneto-optical Kerr microscope show that the magnetic domain wall motion of the films can be controlled by different substrate and buffer layer conditions. It was expected that ultra-fast magnetic moment switching can be achieved by optimizing the conditions to reduce the power consumption of the device. The experimental results also show that the optimized film conditions can also obtain strong PMA on the flexible substrate. These findings help to understand magnetic properties in these structures and show the promising prospect for wearable devices and other spintronic devices.

关键词： Pt/Co stacks perpendicular magnetic anisotropy magnetodynamic behavior spintronics flexible devices high temperature deposition

Femtosecond laser-assisted switching in perpendicular magnetic tunnel junctions with double-interface free layer

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Science China(Information Sciences) 2022年第4期65卷 251-257页

作者： Luding WANG Wenlong CAI Kaihua CAO Kewen SHI Bert KOOPMANS weisheng zhao Fert Beijing Institute School of Integrated Circuit Science and Engineering Beihang University Department of Applied Physics Institute for Photonic Integration Eindhoven University of Technology

Perpendicular magnetic tunnel junctions with double-interface free layer(p-DMTJs), which exhibit enhanced tunnel magnetoresistance(TMR) and thermal stability(△) at the nanoscale, have received considerable interest as building blocks for spintronic data storage devices. Heat-assisted magnetic recording(HAMR) techniques have been widely employed in mainstream magnetic storage to enable ultrahigh storage density. However, the data access is achieved by sensing the stray field of the selected magnetic element using a mechanical “read head”, resulting in an unfavorable speed limitation and design complexity. To address this issue, integrating laser-assisted switching with a high-performance magnetic tunnel junction has received interest in spintronic R&D; however, it has not yet been achieved. In this study, we experimentally explored femtosecond(fs) laser-assisted switching in a p-DMTJ device using a direct electrical TMR readout. We demonstrate two reconfigurable switching operations, i.e., binary “write” and unidirectional “reset”, by the interplay of the fs laser and synchronized magnetic field sequence. We further explored the joint effect, and a switching phase diagram was obtained. The effect of the stray field of p-DMTJ, as well as laser helicity,on switching is also discussed. Results show the feasibility of fs laser-assisted writing p-DMTJs, which can pave the way in high-density optospintronic storage applications.

关键词： magnetic tunnel junctions (MTJs) heat-assisted magnetic recording (HAMR) spintronics femtosecond laser thermally-assisted switching (TAS)

Large spin Hall effect and tunneling magnetoresistance in iridium-based magnetic tunnel junctions

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Science China(Physics,Mechanics & Astronomy) 2020年第1期63卷 86-92页

作者： JiaQi Zhou Hang Yu Zhou Arnaud Boumel weisheng zhaop Fert Beijing Institute BDBCSchool of MicroelectronicsBeihang UniversityBeijing 100191China Centre de Nanosciences et de Nanotechnologies CNRSUniversite Paris-SudUniversite Paris-SaclayPalaiseau 91120France

Magnetic tunnel junctions(MTJs)switched by spin-orbit torque(SOT)have attracted substantial interest owing to their advantages of ultrahigh speed and prolonged *** field-free magnetization switching and high tunneling magnetoresistance(TMR)are critical for the practical application of SOT magnetic random access memory(MRAM).In this work,we propose an MTJ structure based on an iridium(Ir)bottom *** metal is a desirable candidate for field-free SOT switching owing to its strong intrinsic spin Hall conductivity(SHC),which can be enhanced via ***,we study TMR in Ir-based MTJs with symmetric and asymmetric ***-based MTJs exhibit large TMR,which can be further enhanced by heavy metal symmetry owing to the resonant tunneling *** comprehensive investigations illustrate that Ir-based MTJs are promising candidates for realizing SOT switching and high TMR.

关键词： magnetic tunnel junction spin Hall effect tunneling magnetoresistance

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Neuromorphic terahertz imaging based on carbon nanotube circuits

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Science China(Information Sciences) 2023年第6期66卷 303-304页

作者： Nan YANG Zhizhong SI Xinhe WANG Xiaoyang LIN weisheng zhao School of Integrated Circuit Science and Engineering Beihang University Fert Beijing Institute MIIT Key Laboratory of SpintronicsSchool of Integrated Circuit Science and EngineeringBeihang University

We propose a neuromorphic THz imaging system based on the integration of carbon nanotubes(CNTs) circuits and the spin-transfer torque magnetic tunnel junctions(STTMTJs). Utilizing the photothermoelectric effect of CNT...

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Stateful implication logic based on perpendicular magnetic tunnel junctions

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Science China(Information Sciences) 2022年第2期65卷 197-203页

作者： Wenlong CAI Mengxing WANG Kaihua CAO Huaiwen YANG Shouzhong PENG Huisong LI weisheng zhao Fert Beijing Institute MIIT Key Laboratory of Spintronics School of Integrated Circuit Science and EngineeringBeihang University Beihang-Goertek Joint Microelectronics Institute Qingdao Research Institute Beihang University

As the conventional von Neumann architecture meets critical limitations of data transfer bandwidth and energy consumption, perpendicular magnetic anisotropy magnetic tunnel junction based processing-in-memory paradigm attracts extensive attention as a promising substitute thanks to its nonvolatility, low-power switching, fast access and infinite endurance. In this work, we propose and experimentally demonstrate a new spintronic implication logic gate that consists of two parallel perpendicular magnetic anisotropy magnetic tunnel junctions with different diameters. Material implication and furthermore NAND logic functions are implemented by all electrically-controlled operations. The reliability of this structure is verified, especially in sub-20 nm node, which shows great potential for large-density processing-in-memory applications.

关键词： perpendicular magnetic anisotropy magnetic tunnel junction implication spin transfer torque spintronic implication logic gate processing-in-memory

Prototyping federated learning on edge computing systems

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Frontiers of Computer Science 2020年第6期14卷 185-187页

作者： Jianlei YANG Yixiao DUAN Tong QIAO Huanyu ZHOU Jingyuan WANG weisheng zhao School of Computer Science and Engineering Beihang UniversityBeijing 100191China Fert Beijing Research Institute BDBCBeihang UniversityBeijing 100191China School of Microelectronics Beihang UniversityBeijing 100191China

1 Introduction Deep learning has obtained a great success in computing technologies and has been afiliated to people's lives insepa-rably recent ***,the most common approach to deploy these deep learning models is to collect the users data and train them in central ***,the users data might be inevitably undermined during the process of col-lection and uploading,and users sensitive information might be exposed to *** at reducing the risk of privacy leakage,Google proposed federated learning,which has been successfully applied to several applications,e.g.,data alliance among enterprises[1],next word prediction in Gboard[2],etc.

关键词： prediction computing learning

Spintronics intelligent devices

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Science China(Physics,Mechanics & Astronomy) 2023年第11期66卷 17-43页

作者： Wenlong Cai Yan Huang Xueying Zhang Shihong Wang Yuanhao Pan Jialiang Yin Kewen Shi weisheng zhao Fert Beijing Institute MIIT Key Laboratory of SpintronicsSchool of Integrated Circuit Science and EngineeringBeihang UniversityBeijing100191China Beihang-Goertek Joint Microelectronics Institute Qingdao Research InstituteBeihang UniversityQingdao266000China

Intelligent computing paradigms have become increasingly important for the efficient processing of massive amounts of ***,using traditional electronic devices to implement these intelligent paradigms is currently mismatched and limited by their energy,area,and ***,which exploits the magnetic and electrical properties of electrons,could break through these limitations and bring new possibilities to electrical *** particular,the tunneling magnetoresistance effect,merging quantum and spintronics,enables spintronic devices to be compatible with standard integrated circuits with a magnetic tunnel junction(MTJ)design,showing great potential for implementing hardware-based intelligent *** this review,we introduce the specific capabilities of MTJs,including nonvolatility,stochasticity,plasticity,and nonlinearity,which are highly favorable in artificial intelligence *** then present how these devices could impact the development of intelligent computing,including in-memory computing,probabilistic computing,and neuromorphic ***,we discuss their challenges and perspectives in intelligent hardware implementations.

关键词： tunneling magnetoresistance effect magnetic tunnel junction in-memory computing probabilistic computing neuromorphic computing

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