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Field-free spin-orbit torque perpendicular magnetization switching in ultrathin nanostructures

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npj Computational Materials 2020年第1期6卷 1004-1013页

作者： Minyi Dai Jia-mian hu Department of Materials Science and Engineering University of Wisconsin-MadisonMadisonWI 53705USA

Magnetic-field-free current-controlled switching of perpendicular magnetization via spin-orbit torque(SOT)is necessary for developing a fast,long data retention,and high-density SOT magnetoresistive random access memory(MRAM).Here,we use both micromagnetic simulations and atomistic spin dynamics(ASD)simulations to demonstrate an approach to field-free SOT perpendicular magnetization switching without requiring any changes in the architecture of a standard SOT-MRAM *** show that this field-free switching is enabled by a synergistic effect of lateral geometrical confinement,interfacial Dyzaloshinskii–Moriya interaction(DMI),and current-induced *** micromagnetic and atomistic understanding of the nucleation and growth kinetics of the reversed domain are ***,atomically resolved spin dynamics at the early stage of nucleation is revealed using ASD simulations.A machine learning model is trained based on~1000 groups of benchmarked micromagnetic simulation *** machine learning model can be used to rapidly and accurately identify the nanomagnet size,interfacial DMI strength,and the magnitude of current density required for the field-free switching.

关键词： reversed magnetization interfacial

Provenance and drainage system of the Early Cretaceous volcanic detritus in the Himalaya as constrained by detrital zircon geochronology

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Journal of Palaeogeography 2015年第1期4卷 85-98页

作者： Xiu-mian hu Eduardo Garzanti Wei An State Key Laboratory of Mineral Deposits Research School of Earth Sciences and Engineering Nanjing University Department of Earth and Environmental Sciences Università di Milano?BicoccaMilano 20126 Italy

The age range of the major intra-plate volcanic event that affected the northern Indian margin in the Early Cretaceous is here defined precisely by detrital zircon geochronology. U-Pb ages of Early Cretaceous detrital zircons found in the Cretaceous to the Paleocene sandstones cluster mainly between 142 Ma and 123 Ma in the northern Tethys Himalayan unit, and between 140 Ma and 116 Ma in the southern Tethys Himalayan unit. The youngest and oldest detrital zircons within this group indicate that volcanism in the source areas started in the latest Jurassic and ended by the early Albian. Stratigraphic data indicate that volcaniclastic sedimentation began significantly earlier in southern Tibet （Tithonian） than in Nepal （Valangin- ian）, and considerably later in Spiti and Zanskar （Aptian/AIbian） to the west. This apparent westward migration of magmatism was explained with progressive westward propagation of extensional/transtensional tectonic activity and development of fractures cutting deeply across the Indian continental margin crust. However, detrital zircon geochronology provides no indication of heterochroneity in magmatic activity in the source areas from east to west, and thus lends little support to such a scenario. Westward migration of volcaniclastic sedimentation may thus reflect instead the westward progradation of major drainage systems supplying volcanic detritus sourced from the same volcanic centers in the east. Development of multiple radial drainage away from the domal surface uplift associated with magmatic upwelling, as observed for most large igneous provinces around the world, may also explain why U-Pb ages of detrital zircons tend to cluster around 133-132 Ma （the age of the Cornel igneous province） in Tethys Himalayan units, but around 118-117 Ma （the age of the Rajmahal igneous province） in Lesser Himalayan units.

关键词： northern Indian margin Cretaceous Himalayan Orogen volcaniclastic detri-tus drainage system zircon geochronology palaeogeography

Perspective: voltage control of magnetization in multiferroic heterostructures

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National Science Review 2019年第4期6卷 621-624页

作者： Jia-mian hu Ce-Wen Nan Long-Qing Chen Department of Materials Science and Engineering University of Wisconsin–Madison State Key Lab of New Ceramics and Fine Processing School of Materials Science and Engineering Tsinghua University Department of Materials Science and Engineering Pennsylvania State University

Multiferroic materials host ferromagnetic and ferroelectric orders either in the same phase, or separately in distinct magnetic and ferroelectric phases. In some multiferroic materials, the two distinct ferroic orders can be strongly coupled (namely, magnetoelectric coupling)[1], which can be exploited for achieving new functionalities. For example, it allows for controlling magnetization with a voltage rather than a magnetic-field-generating electric current, providing an energy-efficient

关键词： Perspective voltage control of magnetization in multiferroic heterostructures AFM

Strain-mediated voltage-controlled switching of magnetic skyrmions in nanostructures

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npj Computational Materials 2018年第1期4卷 147-153页

作者： Jia-mian hu Tiannan Yang Long-Qing Chen Department of Materials Science and Engineering The Pennsylvania State UniversityUniversity ParkPA 16802USA Department of Materials Science and Engineering University of Wisconsin–MadisonMadisonWI 53706USA

Magnetic skyrmions are swirling spin structures stabilized typically by the Dyzaloshinskii-Moriya *** existing control of magnetic skyrmions has often relied on the use of an electric current,which may cause overheating in densely packed *** we demonstrate,using phase-field simulations,that an isolated Néel skyrmion in a magnetic nanodisk can be repeatedly created and deleted by voltage-induced strains from a juxtaposed *** a skyrmion switching is non-volatile,and consumes only~0.5 fJ per switching which is about five orders of magnitude smaller than that by current-induced *** is found that the strain-mediated skyrmion creation occurs through an intermediate vortex-like spin structure,and that the skyrmion deletion occurs though a homogenous shrinkage during which the Néel wall is temporarily transformed to a *** findings are expected to stimulate experimental research into strain-mediated voltage control of skyrmions,as well as other chiral spin structures for low-power spintronics.

关键词： vortex magnetic repeatedly

Graph neural networks for an accurate and interpretable prediction of the properties of polycrystalline materials

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npj Computational Materials 2021年第1期7卷 925-933页

作者： Minyi Dai Mehmet F.Demirel Yingyu Liang Jia-mian hu Department of Materials Science and Engineering University of Wisconsin-MadisonMadisonWIUSA Department of Computer Sciences University of Wisconsin-MadisonMadisonWIUSA

Various machine learning models have been used to predict the properties of polycrystalline materials,but none of them directly consider the physical interactions among neighboring grains despite such microscopic interactions critically determining macroscopic material ***,we develop a graph neural network(GNN)model for obtaining an embedding of polycrystalline microstructure which incorporates not only the physical features of individual grains but also their *** embedding is then linked to the target property using a feed-forward neural *** the magnetostriction of polycrystalline Tb_(0.3)Dy_(0.7)Fe_(2) alloys as an example,we show that a single GNN model with fixed network architecture and hyperparameters allows for a low prediction error of~10%over a group of remarkably different microstructures as well as quantifying the importance of each feature in each grain of a microstructure to its *** a microstructure-graph-based GNN model,therefore,enables an accurate and interpretable prediction of the properties of polycrystalline materials.

关键词： microstructure polycrystalline prediction

A simplified approximate analytical model for Rayleigh-Taylor instability in elastic-plastic solid and viscous fluid with thicknesses

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Chinese Physics B 2021年第4期30卷 342-350页

作者： Xi Wang Xiao-mian hu Sheng-Tao Wang Hao Pan Institute of Applied Physics and Computational Mathematics Beijing 100094China Center for Applied Physics and Technology Peking UniversityBeijing 100871China

A simplified theoretical model for the linear Rayleigh-Taylor instability of finite thickness elastic-plastic solid constantly accelerated by finite thickness viscous fluid is *** the irrotational assumption,it is possible to consider viscosity,surface tension,elasticity or plasticity effects *** model considers thicknesses at rigid wall boundary conditions with the velocity potentials,and deals with solid elastic-plastic transition and fluid viscosity based on the velocity continuity and force equilibrium at contact *** complete analytical expressions of the amplitude motion equation,the growth rate,and the instability boundary are obtained for arbitrary Atwood number,viscosity,thicknesses of solid and *** thicknesses effects of two materials on the growth rate and the instability boundary are discussed.

关键词： Rayleigh-Taylor instability viscosity plasticity thicknesses effects

Understanding and designing magnetoelectric heterostructures guided by computation:progresses,remaining questions,and perspectives

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npj Computational Materials 2017年第1期3卷 304-324页

作者： Jia-mian hu Chun-Gang Duan Ce-Wen Nan Long-Qing Chen Department of Materials Science and Engineering Pennsylvania State UniversityUniversity ParkPA 16802USA Key Laboratory of Polar Materials and Devices Ministry of EducationEast China Normal UniversityShanghaiChina School of Materials Science and Engineering and State Key Lab of New Ceramics and Fine ProcessingTsinghua UniversityBeijing 100084China

Magnetoelectric composites and heterostructures integrate magnetic and dielectric materials to produce new functionalities,e.g.,magnetoelectric responses that are absent in each of the constituent materials but emerge through the coupling between magnetic order in the magnetic material and electric order in the dielectric *** magnetoelectric coupling in these composites and heterostructures is typically achieved through the exchange of magnetic,electric,or/and elastic energy across the interfaces between the different constituent materials,and the coupling effect is measured by the degree of conversion between magnetic and electric energy in the absence of an electric *** strength of magnetoelectric coupling can be tailored by choosing suited materials for each constituent and by geometrical and microstructural *** this article,we discuss recent progresses on the understanding of magnetoelectric coupling mechanisms and the design of magnetoelectric heterostructures guided by theory and *** outline a number of unsolved issues concerning magnetoelectric *** compile a relatively comprehensive experimental dataset on the magnetoelecric coupling coefficients in both bulk and thin-film magnetoelectric composites and offer a perspective on the data-driven computational design of magnetoelectric composites at the mesoscale microstructure level.

关键词： composites material coupling

Grain-size and compositional variability of Yarlung Tsangpo sand(Xigaze transect,south Tibet):Implications for sediment mixing by fluvial and aeolian processes

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Journal of Palaeogeography 2023年第2期12卷 195-210页

作者： Wen Lai Wen-Dong Liang Xiu-mian hu Eduardo Garzanti hua-Yu Lu Xiao-Long Dong Frontiers Science Center for Critical Earth Material Cycling School of Geography and Ocean ScienceNanjing UniversityNanjing 210023Jiangsu ProvinceChina State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation Institute of Sedimentary GeologyChengdu University of TechnologyChengdu 610059Sichuan ProvinceChina State Key Laboratory of Mineral Deposits Research School of Earth Sciences and EngineeringNanjing UniversityNanjing 210023Jiangsu ProvinceChina Department of Earth and Environmental Sciences Universita di Milano-BicoccaMilano 20126Italy

Studying the grain-size dependent compositional variability in modern river sediments provides a key to decipher the information stored in the sedimentary archive and reconstruct the evolution of the Earth’s surface in the past. Bedload sand along the Xigaze cross section of the Yarlung Tsangpo(upper Brahmaputra River) ranges in mean grain size from 0.72 Φ to 3.21 Φ, is moderately to poorly sorted and slightly platykurtic to moderately leptokurtic with sub-angular to sub-spherical grains. Litho-feldspatho-quartzose to feldspatholitho-quartzose sand(Q 43%-65%;F 13%-44%;L 11%-28%) contains 3.4%-14.4% heavy minerals including amphibole(64%-89%), epidote(4%-11%), chloritoid(0-10%), and clinopyroxene(2%-6%). The marked textural and compositional variability observed across the Xigaze transect of the Yarlung Tsangpo mainstem is controlled by both fluvial and aeolian processes, including repeated reworking by westerly and glacial winds,as well as by local contributions from northern and southern tributaries draining the Lhasa Block and the Himalayan Belt, respectively. The modern sedimentary case here will shed new light on interpreting paleogeography and provenance.

关键词： Modern fluvial sediments Sand petrography Heavy minerals Fluvial/aeolian interactions Endmember grain-size modeling Lhasa Block Himalayan Belt

The“underfilled trinity model”of foreland basins revisited:reality or myth?

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Journal of Palaeogeography 2024年第4期13卷 675-705页

作者： Xiu-mian hu Eduardo Garzanti Juan Li Marcelle BouDagher-Fadel Giovanni Coletti An-Lin Ma Wen-Dong Liang Wei-Wei Xue State Key Laboratory of Mineral Deposits Research Institute of Continental GeodynamicsSchool of Earth Sciences and EngineeringNanjing UniversityNanjing 210023China Department of Earth and Environmental Sciences Universitàdi Milano-BicoccaMilano 20126Italy Department of Earth Sciences University College LondonGower StreetLondon WC1E 6BTUK

The“underfilled trinity”model of foreland-basin stratigraphy was proposed based on the observation that the initial sedimentary stages along the western and northern front of the western and central Alps were represented by shallow-water carbonates(Calcaires a Nummulites)overlain by hemipelagic marls(Marnes Bleues)and capped by siliciclastic turbidites(Gr es d'Annot).Subsequently,this model has been widely accepted and applied in foreland basins *** here re-investigated the Eocene-Oligocene sedimentary succession of the Western Alps to check its *** geological features of this region include:i)the existence of a Cretaceous-Eocene unconformity spanning more than 25 Myr in the studied sections;ii)a virtually synchronous age of the Calcaires a Nummulites,Marnes Bleues,and Gr es d'Annot formations across the Western Alps;iii)a long-term deepening-upward trend,from inner to outer ramp,documented by the Calcaires a Nummulites,followed by the pelagic Marnes Bleues and by the Gr es d'Annot turbidites;iv)the provenance of the Gr es d'Annot Formation from the Maures-Est erel Massif and/or CorsicaSardinia block in the south,rather than from the Alpine orogen in the *** integrating field observations,sedimentological,biostratigraphic,and provenance analyses,we found the Eocene“underfilled foreland”model too simplistic and inadequate to explain the basin evolution in the western Alpine *** on the alternative scenario proposed herein,the Annot and Barr^eme basins formed in the late Eocene(40-35 Ma)in an extensional/transtensional setting during a period of major change in tectonic stress fields across western Europe on the upper plate of the Apennine subduction.

关键词： Western Alps Paleogene Annot basin Foreland-basin models Flysch and molasse stages Apenninic subduction