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Nanoscale control of low-dimensional spin structures in manganites

Chinese Physics B 2016年第6期25卷 45-52页

作者：王静 iftikhar ahmed malik 梁仁荣黄文郑仁奎张金星 Department of Physics Beijing Normal University Beijing 100875 China Tsinghua National Laboratory for Information Science and Technology Institute of Microelectronics Tsinghua University Beijing 100084 China School of Microelectronics and Solid-State Electronics University of Electronic Science and Technology of China Chengdu 611731 China State Key Laboratory of High Performance Ceramics and Superfine Microstructure Shanghai Institute of Ceramics Chinese Academy of Sciences Shanghai 200050 China

Due to the upcoming demands of next-generation electronic/magnetoelectronic devices with low-energy consumption,emerging correlated materials（such as superconductors,topological insulators and manganites） are one of the highly promising candidates for the *** the past decades,manganites have attracted great interest due to the colossal magnetoresistance effect,charge-spin-orbital ordering,and electronic phase ***,the incapable of deterministic control of those emerging low-dimensional spin structures at ambient condition restrict their possible ***,the understanding and control of the dynamic behaviors of spin order parameters at nanoscale in manganites under external stimuli with low energy consumption,especially at room temperature is highly *** this review,we collected recent major progresses of nanoscale control of spin structures in manganites at low dimension,especially focusing on the control of their phase boundaries,domain walls as well as the topological spin structures（e.g.,skyrmions）.In addition,capacitor-based prototype spintronic devices are proposed by taking advantage of the above control methods in *** capacitor-based structure may provide a new platform for the design of future spintronic devices with low-energy consumption.

关键词： manganites spin structures nanoscale phase boundary domain wall skyrmion spintronic device capacitor

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Inhomogeneous-strain-induced magnetic vortex cluster in one-dimensional manganite wire

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Science Bulletin 2020年第3期65卷 201-207页

作者： iftikhar ahmed malik Houbing Huang Yu Wang Xueyun Wang Cui Xiao Yuanwei Sun Rizwan Ullah Yuelin Zhang Jing Wang Muhammad Abdullah malik Irfan ahmed Changmin Xiong Simone Finizio Mathias Kl?ui Peng Gao Jie Wang Jinxing Zhang Department of Physics Beijing Normal UniversityBeijing 100875China Advanced Research Institute of Multidisciplinary Science Beijing Institute of TechnologyBeijing 100081China Department of Engineering Mechanics&Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province Zhejiang UniversityHangzhou 310027China School of Aerospace Engineering Beijing Institute of TechnologyBeijing 100081China Department of Physics University of Science and Technology BeijingBeijing 100083China International Center for Quantum Materials and Electron Microscopy Laboratory School of PhysicsPeking UniversityBeijing 100871China Department of Physics Johannes Gutenberg-University MainzMainz 55099Germany Graduate School of Excellence Materials Science in Mainz Mainz 55128Germany Collaborative Innovation Center of Quantum Matter Beijing 100871China

Mixed-valance manganites with strong electron correlation exhibit strong potential for spintronics,where emergent magnetic behaviors,such as propagation of high-frequency spin waves and giant topological Hall Effects can be driven by their mesoscale spin ***,we create magnetic vortex clusters with flux closure spin configurations in single-crystal La0.67Sr0.33MnO3 wire.A distinctive transformation from out-of-plane domains to a vortex state is directly visualized using magnetic force microscopy at 4 K in wires when the width is below 1.0μ*** phase-field modeling indicates that the inhomogeneous strain,accompanying with shape anisotropy,plays a key role for stabilizing the flux-closure spin *** work offers a new perspective for understanding and manipulating the non-trivial spin textures in strongly correlated systems.

关键词： Magnetic vortex cluster Inhomogeneous strain One-dimensional manganites Epitaxial thin films Cryo-Temperature MFM

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Solid state reaction for the formation of spinel MgFe_2O_4 across perovskite oxide interface

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Science China(Physics,Mechanics & Astronomy) 2017年第9期60卷 80-84页

作者： iftikhar ahmed malik XiaoXing Ke Xin Liu ChuanShou Wang XueYun Wang Rizwan Ullah ChuangYe Song Jing Wang JinXing Zhang Department of Physics Beijing Normal University Institute of Microstructure and Property of Advanced Materials Beijing University of Technology Department of Physics University of Science and Technology Beijing

Solid state reaction is a conventional method to synthesize structurally stable inorganic solids by mixing powdered reactants together at high pressure （over 1 x 105 mbar （1 mbar = 100 Pa）） and high temperature （over 1300 K） [1-4]. This method is effective and sophisticated to prepare solid mate- rials, especially the functional complex oxides such as high temperature superconductors, piezoelectrics, dielectrics, etc. However, the chemical reactions cannot be intrinsically con- trolled and integrated at an atomic level in order to achieve the applications of future thin film devices with reduced dimensions [5]. With the desire of designing high-quality products with the micro/nanoscale integration, many pow- erful physical techniques, such as, pulsed-laser deposition （PLD）, molecular beam epitaxy （MBE）, sputtering deposi- tion, etc., have experienced enormous development due to their ability of lattice and/or interfacial controls. Using these growth techniques, layer-by-layer deposition （multilayer and/or superlattice） can be achieved, providing us a platform to tune the crystal structures at an atomic level by controlling the interfacial terminations and epitaxial strain, which are absent in their bulk counterparts [6-8]. From this point of view, well-controlled interfacial structures may also provide the solid state reaction at an atomic level during the physical depositions, which provides us an effective way to design the desired products from the chemical bonding reconstruction.

关键词：固相反应界面形成钙钛矿型氧化物 MgFe2O4 尖晶石脉冲激光沉积高温超导体控制界面

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Hidden metal-insulator transition in manganites synthesized via a controllable oxidation

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Science China Materials 2019年第4期62卷 577-585页

作者： Chuangye Song iftikhar ahmed malik Menglei Li Qinghua Zhang Lichen Wang Jing Wang Rongyan Chen Renkui Zheng Shuai Dong Lin Gu Wenhui Duan Ce-Wen Nan Jinxing Zhang Department of physics Beijing Normal University Department of Physics Capital Normal University Institute of physics Chinese Academy of Sciences School of Materials Science and Engineering Tsinghua University Center for Advanced Quantum Studies Beijing Normal University State Key Laboratory of High Performance Ceramics and Superfine Microstructure Shanghai Institute of Ceramics Chinese Academy of Sciences School of Physics Southeast University Department of Physics and State Key Laboratory of Low-Dimensional Quantum Physics Tsinghua University

Oxygen usually plays crucial roles in tuning the phase structures and functionalities of complex oxides such as high temperature superconductivity, colossal magnetoresistance, catalysis, etc. Effective and considerable control of the oxygen content in those functional oxides could be highly desired. Here, using perovskite manganite(La0.5Sr0.5)MnO3 as a paradigm, we develop a new pathway to synthesize the epitaxial thin films assisted by an in-situ chemical process, where the oxygen content can be precisely controlled by varying oxidative activity tuned by the atmospheric temperature(Tatm)during the growth. A hidden metal-insulator transition(MIT)emerges due to the phase competition, which is never shown in the phase diagram of this classic manganite. The oxygenmediated interaction between Mn ions together with the change of carrier density might be responsible for this emerging phase, which is compatible with the results of firstprinciple calculations. This work demonstrates that, apart from traditional cation doping, a precise modulation of anion(O2-, S2-, etc.) may provide a new strategy to control phase structures and functionalities of epitaxial compound thin films.

关键词： oxidative-activity oxygen-content manganites hidden metal-insulator transition

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Observation of unconventional anomalous Hall effect in epitaxial CrTe thin films

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Nano Research 2018年第6期11卷 3116-3121页

作者： Dapeng Zhao Liguo Zhang iftikhar ahmed malik Menghan Liao Wenqiang Cui Xinqiang Cai Cheng Zheng Luxin Li Xiaopeng Hu Ding Zhang Jinxing Zhang Xi Chen Wanjun Jiang Qikun Xue State Key Laboratory of Low Dimensional Quantum Physics Department of Physics Tsinghua University Beijing 100084 China Department of Physics Beijing Normal University Beijing 100875 China Collaborative Innovation Center of Quantum Matter Beijing 100084 China

We have studied the magnetic and electrical transport properties of epitaxial NiAs-type CrTe thin films grown on SrTiO3（111） substrates. Unlike rectangle hysteresis loops obtained from magnetic measurements, we have identified intriguing extra bump/dip features from anomalous Hall experiments on the films with thicknesses less than 12 nm. This observed Hall anomaly is phenomenologically consistent with the occurrence of a topological Hall effect （THE） in chiral magnets with a skyrmion phase. Furthermore, the THE contribution can be tuned by the film thickness, showing the key contribution of asymmetric interfaces in stabilizing N6el-type skyrmions. Our work demonstrates that a CrTe thin film on SrTiO3（111） substrates is a good material candidate for studying real-space topological transport.

关键词： topological Hall effect CrTe films skyrmion phase molecular beam epitaxy

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Spin quantum well-like behavior in single-crystal Gd0.75La0.25FeO3

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Science China Materials 2021年第2期64卷 531-536页

作者： Xin Wen Zhigang Song iftikhar ahmed malik Yifei Fang Wenyun Yang Jingzhi Han Shunquan Liu Honglin Du Shixun Cao Jinxing Zhang Xiangqun Zhang Zhaohua Cheng Yanglong Hou Jinbo Yang State Key Laboratory for Mesoscopic Physics and School of Physics Peking UniversityBeijing100871China Department of Physics Beijing Normal UniversityBeijing100875China Department of Physics Fudan UniversityShanghai200433China Yifei Fang方依霏Beijing Key Laboratory for Magnetoelectric Materials and Devices Beijing100871China Department of Physics Shanghai UniversityShanghai200444China State Key Laboratory of Magnetism Institute of PhysicsChinese Academy of SciencesBeijing100080China Department of Materials Science and Engineering College of EngineeringPeking UniversityBeijing100871China

Rare earth orthoferrites(RFeO3,R=Y,Gd,Sm,Nd)have recently attracted much attention due to their novel magnetic and electrical properties such as magneto-electrics,*** magneto-optics[1-3].The complex interactions between the two sublattices of R^3+and Fe^3+in RFeO3 provide the feasibility of control-ling spins in these solids,which makes them promising candidates for the spintronics[4].

关键词：磁有序 LaFeO3 量子阱信息存储磁矩特定方向可控性反铁磁

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A Novel Fractional Dengue Transmission Model in the Presence of Wolbachia Using Stochastic Based Artificial Neural Network

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Computer Modeling in Engineering & Sciences 2024年第5期139卷 1217-1238页

作者： Zeshan Faiz iftikhar ahmed Dumitru Baleanu Shumaila Javeed Department of Mathematics COMSATS University IslamabadIslamabad45550Pakistan Department of Mathematics Cankaya UniversityAnkara06790Turkey Institute of Space Sciences Magurele-Bucharest077125Romania Department of Medical Research China Medical University HospitalChina Medical UniversityTaichung40402Taiwan Department of Computer Science and Mathematics Lebanese American UniversityBeirut135053Lebanon Department of Mathematics Mathematics Research CenterNear East UniversityNicosia/Mersin99138Turkey

The purpose of this research work is to investigate the numerical solutions of the fractional dengue transmission model(FDTM)in the presence of Wolbachia using the stochastic-based Levenberg-Marquardt neural network(LM-NN)*** fractional dengue transmission model(FDTM)consists of 12 *** human population is divided into four compartments;susceptible humans(S_(h)),exposed humans(E_(h)),infectious humans(I_(h)),and recovered humans(R_(h)).Wolbachia-infected and Wolbachia-uninfected mosquito population is also divided into four compartments:aquatic(eggs,larvae,pupae),susceptible,exposed,and *** investigated three different cases of vertical transmission probability(η),namely when Wolbachia-free mosquitoes persist only(η=0.6),when both types of mosquitoes persist(η=0.8),and when Wolbachia-carrying mosquitoes persist only(η=1).The objective of this study is to investigate the effectiveness of Wolbachia in reducing dengue and presenting the numerical results by using the stochastic structure LM-NN approach with 10 hidden layers of neurons for three different cases of the fractional order derivatives(α=0.4,0.6,0.8).LM-NN approach includes a training,validation,and testing procedure to minimize the mean square error(MSE)values using the reference dataset(obtained by solving the model using the Adams-Bashforth-Moulton method(ABM).The distribution of data is 80% data for training,10% for validation,and,10% for testing purpose)results.A comprehensive investigation is accessible to observe the competence,precision,capacity,and efficiency of the suggested LM-NN approach by executing the MSE,state transitions findings,and regression *** effectiveness of the LM-NN approach for solving the FDTM is demonstrated by the overlap of the findings with trustworthy measures,which achieves a precision of up to 10^(-4).

关键词： Wolbachia dengue neural network vertical transmission mean square error Levenberg-Marquardt

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Pregnancy stressors and postpartum symptoms of depression and anxiety:the moderating role of a cognitivebehavioural therapy(CBT)intervention

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General Psychiatry 2024年第1期37卷 112-121页

作者： Yunxiang Sun Soim Park Abid malik Najia Atif ahmed Zaidi Atif Rahman Pamela J Surkan Department of International Health Johns Hopkins University Bloomberg School of Public HealthBaltimoreMarylandUSA Department of Public Mental Health Health Services AcademyIslamabadPakistan Human Development Research Foundation RawalpindiPakistan Department of Primary Care and Mental Health Institute of Population HealthUniversity of LiverpoolLiverpoolUK

Background Little is known about the association between stressors(especially positive stressors)during pregnancy and postpartum depression and *** We investigated the association between positive and negative stress events during different stages of pregnancy and postpartum mental health outcomes among low-income pregnant women with symptoms of anxiety in Pakistan and evaluated whether an intervention based on cognitive behavioural therapy(CBT)had a regulatory *** Participants were 621 pregnant Pakistani women with mild *** the Pregnancy Experience Scale-Brief Version,six scores were created to assess positive and negative *** performed a multivariate linear regression to examine whether these six scores,measured both at baseline and in the third trimester,were associated with postpartum anxiety and depressive *** effect of the intervention on this relationship was examined by adding an interaction term to the regression *** Hassles frequency measured in the third trimester was positively associated with depression(B=0.22,95%confidence interval(Cl):0.09 to 0.36)and anxiety(B=0.19,95%Cl:0.08to 0.30).At the same timepoint,uplifts intensity was negatively associated with symptoms of depression(B=-0.82,95%Cl:1.46 to-0.18)and anxiety(B=-0.70,95%Cl:-1.25 to-0.15),whereas hassles intensity was positively related to symptoms of depression(B=1.02,95%Cl:0.36 to 1.67)and anxiety(B=0.90,95%Cl:0.34 to 1.47).The intensity ratio of hassles to uplifts reported in the third trimester was positively related to both depression(B=1.40,95%Cl:0.59 to 2.20)and anxiety(B=1.26,95%Cl:0.57 to 1.96).The intervention strengthened the overall positive effects of uplfts and the negative effects of *** experiences at baseline during early pregnancy to mid-pregnancy were not associated with mental health *** Stressors in the third trimester but not earlier in pregnancy were associated with postpartum symptoms

关键词： postpartum stress behaviour

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Cambrian integrative stratigraphy,biotas,and paleogeographical evolution of the Qinghai-Tibetan Plateau and its surrounding areas

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Science China Earth Sciences 2024年第4期67卷 950-970页

作者： Zhixin SUN Lang SUN Fangchen ZHAO Bing PAN malik Muhammad Saud Sajid KHAN Shehryar ahmed Chuan YANG Lanyun MIAO Zongjun YIN Guoxiang LI Maoyan ZHU State Key Laboratory of Palaeobiology and Stratigraphy Nanjing Institute of Geology and PalaeontologyChinese Academy of SciencesNanjing 210008China College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijing 100049China

The Qinghai-Tibetan Plateau and its surrounding areas have a long and complex tectonic evolutionary *** and blocks,such as northern India,Lhasa,Qiangtang,Qaidam and Central Qilian,and their in-between orogenic belts constitute the main part of the Qinghai-Tibetan *** the Cambrian Period,most of these cratons and blocks were on the northwestern periphery of Gondwana,and were associated with the surrounding blocks,***,Central Iran,Afghanistan,Tarim,Alxa,North China,South China and Sibumasu through the Proto-Tethys *** Cambrian stratigraphic sequences on these stable blocks are composed of mixed siliciclastic and carbonate rocks deposited in the shallow-water marine environments,and contain the trilobite assemblages of shelf *** Cambrian stratigraphic sequences in the Qilian tectonic belts,however,are characterized by the intermediate-basic igneous rocks and silicates formed in the Proto-Tethys Ocean,and contain the trilobite assemblages of deep-water slope *** with previous data,field observations and newly discovered fossils through funding by the Second Tibetan Plateau Scientific Expedition and Research,the general characteristics of the Cambrian strata in different tectonic units of the Qinghai-Tibetan Plateau and its surrounding areas have been summarized in this ***,efforts have been made to subdivide and correlate the Cambrian strata across these areas by utilizing available biostratigraphic and geochronological *** a result,a comprehensive litho-and biostratigraphy chart has been ***,from the biogeographic perspective,this paper also provides a brief overview of the Cambrian paleogeographical reconstruction of the major tectonic blocks,and discusses the problems associated with the evolution of the ProtoTethys tectonic belt.

关键词： Qinghai-Tibetan Plateau Cambrian Stratigraphy Paleogeography Biota Gondwana Proto-Tethys Ocean

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Cryogenian and Ediacaran integrative stratigraphy,biotas,and paleogeographical evolution of the Qinghai-Tibetan Plateau and its surrounding areas

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Science China Earth Sciences 2024年第4期67卷 919-949页

作者： Lang SUN malik Muhammad Saud Sajid KHAN Chuan YANG Zhixin SUN Bing PAN Shehryar ahmed Lanyun MIAO Weichen SUN Chunlin HU Xiaojuan SUN Cui LUO Bo CHEN Zongjun YIN Fangchen ZHAO Guoxiang LI Maoyan ZHU State Key Laboratory of Palaeobiology and Stratigraphy Nanjing Institute of Geology and PalaeontologyChinese Academy of SciencesNanjing 210008China College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijing 100049China

The complex evolutionary history of the Qinghai-Tibetan Plateau and its surrounding areas,including the continental blocks(Indian,Lhasa,South Qiangtang,Tarim,Olongbuluk,Central Qilian,Alxa,North China,Yangtze,Central Iran and Oman)and the orogenic belts between them,has long been the frontier in Earth science *** Cryogenian and Ediacaran strata are extensively distributed in these ***,relatively complete Cryogenian and Ediacaran successions have been discovered in Oman,Indian,Yangtze,and Tarim blocks,while only the Ediacaran successions have been reported in Iran,the South Qiangtang,Central Qilian,Alxa,and North China *** on previous studies together with the integration of new materials and advancement obtained through the Second Tibetan Plateau Scientific Expedition and Research,this review aims to synthesize a correlative stratigraphic framework of the representative Cryogenian and Ediacaran sequences from the Qinghai-Tibetan Plateau and its surrounding ***,the Cryogenian and Ediacaran biotas and major geological events in these areas are comprehensively discussed in aspects of current research *** results indicate that,in general,Ediacaran fossils of each area exhibit distinct features in preservation and assemblage composition,but the typical late Ediacaran fossils Cloudina and Shaanxilithes have been reported from most of these *** addition to the two global Cryogenian glaciations,late Ediacaran glaciogenic deposits are extensively recorded in the areas within and around the northern QinghaiTibetan Plateau(including the North China,Alxa,Central Qilian,Olongbuluk,and Tarim blocks,and the North Qilian Accretionary Belt),as well as central and southern ***,further research is required to determine the age,distribution,and origin of these late Ediacaran glaciogenic ***,the middle Ediacaran DOUNCE/Shuram Excursion is widely documented in the Qinghai-Tibetan Plateau and its surroundi

关键词： Qinghai-Tibetan Plateau Cryogenian Ediacaran Stratigraphy Palaeogeography Biota Gondwana

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