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Electric field induced magnetization reversal in magnet/insulator nanoheterostructure

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International Journal of Smart and Nano Materials 2020年第3期11卷 298-309页

作者： Qihua Gong Min Yi bai-xiang xu Institute of Materials Science Technische Universität DarmstadtDarmstadtGermany State Key Lab of Mechanics and Control of Mechanical Structures&Key Lab for Intelligent Nano Materials and Devices of Ministry of Education&College of Aerospace Engineering Nanjing University of Aeronautics and Astronautics(NUAA)NanjingChina

Electric-field control of magnetization reversal is promising for lowpower *** in a magnet/insulator nanoheterostructure which is the fundamental unit of magnetic tunneling junction in spintronics,we demonstrate the electric field induced 180°magne-tization switching through a multiscale study combining firstprinciples calculations and finite-temperature magnetization *** the model nanoheterostructure MgO/Fe/Cu with insu-lator MgO,soft nanomagnet Fe and capping layer Cu,through firstprinciples calculations we find its magnetocrystalline anisotropy linearly varying with the electric *** finite-temperature magnetization dynamics which is informed by the first-principles results,we disclose that a room-temperature 180°magnetization switching with switching probability higher than 90%is achievable by controlling the electric-field pulse and the nanoheterostructure *** 180°switching could be fast realized within 5 *** study is useful for the design of low-power,fast,and miniaturized nanoscale electric-field-controlled spintronics.

关键词： Magnetization reversal nanoheterostructure electric field spintronics multiscale simulations switching probability

3D non-isothermal phase-field simulation of microstructure evolution during selective laser sintering

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npj Computational Materials 2019年第1期5卷 442-453页

作者： Yangyiwei Yang Olav Ragnvaldsen Yang bai Min Yi bai-xiang xu Mechanics of Functional Materials Division Institute of Materials ScienceTechnische Universität Darmstadt64287 DarmstadtGermany Department of Materials Science and Engineering Norwegian University of Science and Technology7491 TrondheimNorway State Key Laboratory of Mechanics and Control of Mechanical Structures&Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education&College of Aerospace Engineering Nanjing University of Aeronautics and Astronautics(NUAA)210016 NanjingChina

During selective laser sintering(SLS),the microstructure evolution and local temperature variation interact *** of conventional isothermal sintering model is thereby insufficient to describe *** this work,we construct our model from entropy level,and derive the non-isothermal kinetics for order parameters along with the heat transfer equation coupled with microstructure *** from partial melting and laser-powder interaction are also *** then perform 3D finite element non-isothermal phase-field simulations of the SLS single *** confront the high computation cost,we propose a novel algorithm analogy to minimum coloring problem and manage to simulate a system of 200 grains with grain tracking algorithm using as low as 8 non-conserved order ***,applying the model to SLS of the stainless steel 316L powder,we identify the influences of laser power and scan speed on microstructural features,including the porosity,surface morphology,temperature profile,grain geometry,and *** further validate the first-order kinetics of the transient porosity during densification,and demonstrate the applicability of the developed model in predicting the linkage of densification factor to the specific energy input during SLS.

关键词： microstructure isothermal kinetics

Tailoring magnetic hysteresis of additive manufactured Fe-Ni permalloy via multiphysics-multiscale simulations of process-property relationships

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npj Computational Materials 2023年第1期9卷 1297-1315页

作者： Yangyiwei Yang Timileyin David Oyedeji Xiandong Zhou Karsten Albe bai-xiang xu Mechanics of Functional Materials Division Institute of Materials ScienceTechnische Universität DarmstadtDarmstadt 64287Germany Failure Mechanics and Engineering Disaster Prevention Key Laboratory of Sichuan Province College of Architecture and EnvironmentSichuan UniversityChengdu 610207China Materials Modelling Division Institute of Materials ScienceTechnische Universität DarmstadtDarmstadt 64287Germany

Designing the microstructure of Fe-Ni permalloy produced by additive manufacturing(AM)opens new avenues to tailor its magnetic ***,AM-produced parts suffer from spatially inhomogeneous thermal-mechanical and magnetic responses,which are less investigated in terms of process modeling and *** present a powder-resolved multiphysics-multiscale simulation scheme for describing magnetic hysteresis in AM-produced material,explicitly considering the coupled thermal-structural evolution with associated thermo-elasto-plastic behaviors and chemical order-disorder *** residual stress is identified as the key thread in connecting the physical processes and phenomena across *** employing this scheme,we investigate the dependence of the fusion zone size,the residual stress and plastic strain,and the magnetic hysteresis of AM-produced Fe_(21.5)Ni_(78.5) on beam power and scan *** results also suggest a phenomenological relation between magnetic coercivity and average residual stress,which can guide the magnetic hysteresis design of soft magnetic materials by choosing appropriate processing parameters.

关键词： alloy microstructure hysteresis

A deep learned nanowire segmentation model using synthetic data augmentation

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npj Computational Materials 2022年第1期8卷 845-856页

作者： Binbin Lin Nima Emami David A.Santos Yuting Luo Sarbajit Banerjee bai-xiang xu Mechanics of Functional Materials Division Institute of Materials ScienceTechnische Universität Darmstadt64287DarmstadtGermany Department of Chemistry Texas A&M UniversityCollege StationTX77843USA

Automated particle segmentation and feature analysis of experimental image data are indispensable for data-driven material *** learning-based image segmentation algorithms are promising techniques to achieve this goal but are challenging to use due to the acquisition of a large number of training *** the present work,synthetic images are applied,resembling the experimental images in terms of geometrical and visual features,to train the state-of-art Mask region-based convolutional neural networks to segment vanadium pentoxide nanowires,a cathode material within optical density-based images acquired using *** results demonstrate the instance segmentation power in real optical intensity-based spectromicroscopy images of complex nanowires in overlapped networks and provide reliable statistical *** model can further be used to segment nanowires in scanning electron microscopy images,which are fundamentally different from the training dataset known to the *** proposed methodology can be extended to any optical intensity-based images of variable particle morphology,material class,and beyond.

关键词： nanowires networks particle

Lossless multi-scale constitutive elastic relations with artificial intelligence

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npj Computational Materials 2022年第1期8卷 638-649页

作者： Jaber Rezaei Mianroodi Shahed Rezaei Nima H.Siboni bai-xiang xu Dierk Raabe Microstructure Physics and Alloy Design Max-Planck-Institut für EisenforschungDüsseldorfGermany Ergodic Labs Lohmühlenstraße 6512435BerlinGermany Mechanics of Functional Materials Division Institute of Materials ScienceTechnische Universität DarmstadtDarmstadtGermany

A seamless and lossless transition of the constitutive description of the elastic response of materials between atomic and continuum scales has been so far *** we show how this problem can be overcome by using artificial intelligence(AI).A convolutional neural network(CNN)model is trained,by taking the structure image of a nanoporous material as input and the corresponding elasticity tensor,calculated from molecular statics(MS),as *** with the atomistic data,the CNN model captures the size-and pore-dependency of the material’s elastic properties which,on the physics side,derive from its intrinsic stiffness as well as from surface relaxation and non-local *** demonstrate the accuracy and the efficiency of the trained CNN model,a finite element method(FEM)-based result of an elastically deformed nanoporous beam equipped with the CNN as constitutive law is compared with that obtained by a full atomistic *** trained CNN model predicts the elasticity tensor in the test dataset with a root-mean-square error of 2.4 GPa(3.0%of the bulk modulus)when compared to atomistic *** the other hand,the CNN model is about 230 times faster than the MS calculation and does not require changing simulation methods between different *** efficiency of the CNN evaluation together with the preservation of important atomistic effects makes the trained model an effective atomistically informed constitutive model for macroscopic simulations of nanoporous materials,optimization of nanostructures,and the solution of inverse problems.

关键词： constitutive artificial elasticity

Modulus spectroscopy for the detection of parallel electric responses in electroceramics

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Journal of Materiomics 2022年第3期8卷 556-569页

作者： Till Fromling Yao Liu An-Phuc Hoang Maximillian Gehringer Sebastian Steiner Mikalai Zhuk Julia Glaum bai-xiang xu Department of Materials and Earth Science Technical University of DarmstadtFG Nichtmetallisch-Anorganische WerkstoffeAlarich-Weiss-Straße 264287DarmstadtGermany Department of Materials and Earth Science Technical University of DarmstadtFG Mechanics of Functional MaterialsOtto-Berndt-Straße 364287DarmstadtGermany Department of Materials Science and Engineering Norwegian University of Science and Technology(NTNU)Functional Materials and Materials Chemistry Group(FACET)Sem Sælands Vei 127491TrondheimNorway

Impedance spectroscopy has become one of the most versatile and essential investigation methods concerning electrical properties of materials for electronic and energy *** knowledge about physical mechanisms,however,often demands excellent expertise in evaluating the *** different representations of the same data set can help elucidate the underlying physics,but this is rarely *** this work,the importance of using the modulus representation to identify parallel electric responses is *** responses result from parallel conducting pathways,e.g.,at grain boundaries,or from regions with differing permittivity,e.g.,in *** and quantitative data can be obtained,as it is illustrated based on experimental data from electroceramics and respective physical simulation results using the finite element *** findings should help to study intricate electric responses of materials with chemical or structural heterogeneity.

关键词： ceramics spectroscopy versatile

Simultaneous integration of Fe clusters and NiFe dual single atoms in nitrogen-doped carbon for oxygen reduction reaction

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Nano Research 2024年第4期17卷 2291-2297页

作者： Jirong bai Yuebin Lian Yaoyao Deng Mei xiang Peng xu Quanfa Zhou Yawen Tang Yaqiong Su Research Center of Secondary Resources and Environment School of Chemical Engineering and MaterialsChangzhou Institute of TechnologyChangzhou 213022China Jiangsu Key Laboratory of New Power Batteries School of Chemistry and Materials ScienceNanjing Normal UniversityNanjing 210023China School of Chemistry Engineering Research Center of Energy Storage Materials and Devices of Ministry of EducationNational Innovation Platform(Center)for Industry-Education Integration of Energy Storage TechnologyXi’an Jiaotong UniversityXi’an 710049China

Atomically-dispersed iron-based electrocatalysts are promising substitutes for noble metal electrocatalysts because of excellent performance in oxygen reduction reaction(ORR).Rationally modulating the local coordination environment of the Fe site and optimizing the binding energy of oxygen reduction intermediates are effective strategies to optimize ORR ***,we report a new method in which Ni is introduced to construct NiFe dual single atoms and iron nanoclusters loaded on the nitrogen-doped carbon with a highly porous *** design plays a synergistic role of dual single atoms and clusters,optimizes the 3d orbital and Fermi level of Fe,breaks the symmetrical structure of Fe-N_(4),and effectively improves the adsorption/desorption behavior of the oxygen-containing *** tests show FeNCs/NiFeSAs-NC has an excellent intrinsic *** calculations show the oxygen-containing species on the Ni active site will move to the middle of NiFe(bridge site connection)after optimization and that the key step is OH desorption,with a reaction energy of 0.27 *** electron exchange between NiFe-N6 and Fe-cluster is very strong,further indicating the introduction of Ni species and Fe clusters has a regulatory effect on the electronic structure of Fe-N_(4).

关键词： NiFe dual single atoms Fe clusters OH*adsorption energy oxygen reduction reaction

Magnetic and electrical transport study of the intrinsic magnetic topological insulator MnBi_(2)Te_(4)with Ge doping

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Frontiers of physics 2024年第3期19卷 51-59页

作者： Qingwang bai Mingxiang xu School of Physics Southeast UniversityNanjing 211189China

As an intrinsic magnetic topological insulator with magnetic order and non-trivial topological structure,MnBi_(2)Te_(4)is an ideal material for studying exotic topological states such as quantum anomalous Hall effect and topological axion insulating ***,we carry out magnetic and electrical transport measurements on(Mn1–xGex)Bi_(2)Te_(4)(x=0,0.15,0.30,0.45,0.60,and 0.75)single *** is found that with increasing x,the dilution of magnetic moments gradually weakens the antiferromagnetic exchange ***,Ge doping reduces the critical field of ferromagnetic ordering,which may provide a possible way to implement the quantum anomalous Hall effect at lower magnetic *** transport measurements suggest that electrons are the dominant charge carriers,and the carrier density increases with the Ge doping ***,the Kondo effect is observed in the samples with x=0.45,0.60,and *** results suggest that doping germanium is a viable way to tune the magnetic and electrical transport properties of MnBi_(2)Te_(4),opening up the possibility of future applications in magnetic topological insulators.

关键词： MnBi_(2)Te_(4) intrinsic magnetic topological insulator transition points Kondo effect

Boundary Behaviors for a Continuous-state Nonlinear Neveu’s Branching Process

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Acta Mathematica Sinica,English Series 2024年第8期40卷 2005-2016页

作者： Lin Yu bai xu YANG School of Mathematics and Information Science North Minzu UniversityYinchuan 750021P.R.China

By generalizing a criterion of Mufa Chen for Markov jump processes,we establish the necessary and sufficient conditions for the extinction,explosion and coming down from infinity of a continuous-state nonlinear Neveu... 详细信息

关键词： Continuous-state branching process nonlinear branching Neveu’s branching extinction explosion coming down from infinity