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Enhanced hydrogen evolution reaction in FePt film with remanence due to decrease in domain walls

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Rare Metals 2024年第3期43卷 1108-1115页

作者： Hong Hong Dong-Xue Liu Jun Li Jun-Ming Li Li-Qian Wu Bo Yang Qing-Qi Cao Dun-Hui Wang National Laboratory of Solid State Microstructures Collaborative Innovation Center of Advanced MicrostructuresJiangsu Provincial Key Laboratory for NanotechnologySchool of PhysicsNanjing UniversityNanjing210093China Hangzhou Dianzi University Hangzhou310018China Key Laboratory for Anisotropy and Texture of Materials(Ministry of Education) School of Material Science and EngineeringNortheastern UniversityShenyang110819China

As an effective strategy to improve the properties of electrocatalysts,magnetic field-assisted electrocatalytic water splitting has attracted increasing attention ***,the corresponding enhancements mostly depend on the exertion of an external magnetic field during electrochemical reactions,which results in a high cost of industrial production,and makes the magnetic field manipulation of electrocatalysis become a challenging *** this work,instead of the external magnetic field,a bias magnetic field is self-supplied by the remanence state of a ferromagnetic electrocatalyst of *** to the assistance of this bias magnetic field,the FePt film in the remanence state shows the overpotential of 229 mV during hydrogen evolution reaction,which is much lower than that in its demagnetization state(283 mV).Our findings demonstrate that the remanence in ferromagnetic electrocatalysts can improve the catalytic performance,which is attributed to the decrease in domain walls.

关键词： Remanence magnetic domains Electrocatalysis Hydrogen evolution reaction(HER)

Observation of magnetic domain evolution in constrained epitaxial Ni–Mn–Ga thin films on MgO(0 0 1) substrate

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Journal of Materials Science & Technology 2022年第7期102卷 56-65页

作者： Bo Yang Ivan Soldatov Fenghua Chen Yudong Zhang Zongbin Li Haile Yan Rudolf Schäfer Dunhui Wang Claude Esling Xiang Zhao Liang Zuo Key Laboratory for Anisotropy and Texture of Materials(Ministry of Education) School of Material Science and EngineeringNortheastern UniversityShenyang 110819China Institute for Metallic Materials Leibniz Institute for Solid State and Materials Research(IFW)DresdenHelmholtzstrasse 2001069 DresdenGermany Institute of Natural Sciences Ural Federal University620002 EkaterinburgRussia Department of Physics School of Applied ScienceTaiyuan University of Science and TechnologyTaiyuan 030024China Laboratoire d’Étude des Microstructures et de Mécanique des Matériaux(LEM3) CNRS UMR 7239Universitéde Lorraine57045 MetzFrance Institute for Materials Science Dresden University of Technology01062 DresdenGermany National Laboratory of Solid State Microstructures and Jiangsu Key Laboratory for Nanotechnology and Collaborative Innovation Center of Advanced Microstructures Nanjing UniversityNanjing 210093China

Epitaxial Ni–Mn–Ga thin films have promising application potential in micro-electro-mechanical sensing and actuation systems. To date, large abrupt magnetization changes have been observed in some epitaxial Ni–Mn–Ga thin films, but their origin-either from magnetically induced martensite variant reorientation(MIR) or magnetic domain evolution-has been discussed controversially. In the present work, we investigated the evolutions of the magnetic domain and microstructure of a typical epitaxial Ni–Mn–Ga thin film through wide-field magneto-optical Kerr-microscopy. It is demonstrated that the abrupt magnetization changes in the hysteresis loops should be attributed to the magnetic domain evolution instead of the MIR.

关键词： Ni–Mn–Ga thin films magnetic field-induced variant reorientation magnetic domains Magnetization process Magneto-optical Kerr microscopy

Vector analysis of electric-field-induced antiparallel magnetic domain evolution in ferromagnetic/ferroelectric heterostructures

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Journal of Advanced Ceramics 2021年第6期10卷 1273-1281页

作者： Xinger ZHAO Zhongqiang HU Jingen WU Ting FANG Yaojin LI Yuxin CHENG Yifan ZHAO Mengmeng GUAN Dan XIAN Chenying WANG Qi MAO Bin PENG Ren-Ci PENG Ziyao ZHOU Zhiguang WANG Zhuang-De JIANG Ming LIU Electronic Materials Research Laboratory Key Laboratory of the Ministry of Education&International Center for Dielectric ResearchSchool of Electronic Science and EngineeringState Key Laboratory for Mechanical Behavior of MaterialsXi’an Jiaotong UniversityXi’an 710049China Collaborative Innovation Center of High-End Manufacturing Equipment Xi'an Jiaotong UniversityXi’an 710049China International Joint Laboratory for Micro/Nano Manufacturing and Measurement Technology Xi’an Jiaotong UniversityXi’an 710049China

Electric field(E-field)control of magnetism based on magnetoelectric coupling is one of the promising approaches for manipulating the magnetization with low power *** evolution of magnetic domains under in-situ E-fields is significant for the practical applications in integrated micro/nano ***,we report the vector analysis of the E-field-driven antiparallel magnetic domain evolution in FeCoSiB/PMN-PT(011)multiferroic heterostructures via in-situ quantitative magneto-optical Kerr *** is demonstrated that the magnetic domains can be switched to both the 0°and 180°easy directions at the same time by E-fields,resulting in antiparallel magnetization distribution in ferromagnetic/ferroelectric *** antiparallel magnetic domain evolution is attributed to energy minimization with the uniaxial strains by E-fields which can induce the rotation of domains no more than 90°.Moreover,domains can be driven along only one or both easy axis directions by reasonably selecting the initial magnetic domain *** vector analysis of magnetic domain evolution can provide visual insights into the strain-mediated magnetoelectric effect,and promote the fundamental understanding of electrical regulation of magnetism.

关键词： multiferroics magnetoelectric effect magnetic domains magneto-optical Kerr effect(MOICE)

magnetic domain structures of precipitation-hardened SmCo 2:17-type sintered magnets: Heat treatment effect

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Chinese Physics B 2008年第6期17卷 2281-2287页

作者：李岫梅方以坤郭朝晖刘涛郭永权李卫韩宝善 Division of Functional Materials Research Central Iron & Steel Research Institute State Key Laboratory of Magnetism Institute of Physics and the Center for Condensed Matter Physics Chinese Academy of Sciences

The typical magnetic domains of Sm（CObalFe0.25Cuo.07Zr0.02）7.4 magnets quenched through various heattreatment steps have been revealed by using magnetic force microscopy （MFM）. For the specimens in which the nominal c-axis is perpendicular to the imaging plane, the domain configurations change from plate-like for the as-sintered magnet to corrugation and spike-like for the homogenized one, and then to a coarse and finally to a finer domain structure when isothermally aged at 830℃ and then annealed at 400℃. However, only plate-like domains can be detected on the surfaces with the nominal c-axis parallel to the imaging plane. The finer domain （so-called interaction domain） is a characteristic magnetic domain pattern of the SmCo 2：IT-type magnets with high coercivities. Domain walls in a zigzag shape are revealed by means of MFM in final bulk SraCo 2：17-type sintered magnets.

关键词： Sm-Co permanent magnets magnetic domains heat-treatment magnetic force microscopy

Spin switching in antiferromagnets using Néel-order spin-orbit torques

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Chinese Physics B 2018年第10期27卷 88-95页

作者： P Wadley K W Edmonds School of Physics and Astronomy University of Nottingham

Antiferromagnets offer considerable potential for electronic device applications. This article reviews recent demonstrations of spin manipulation in antiferromagnetic devices using applied electrical currents. Due to spin–orbit coupling in environments with particular crystalline or structural symmetries, the electric current can induce an effective magnetic field with a sign that alternates on the lengthscale of the unit cell. The staggered effective field provides an efficient mechanism for switching antiferromagnetic domains and moving antiferromagnetic domain walls, with writing speeds in the terahertz regime.

关键词： spintronics antiferromagnetic current-induced torques magnetic domains

magnetic microstructure and coercivity mechanism of high performance Nd-Fe-B magnets

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Rare Metals 2006年第Z1期25卷 630-632页

作者： ZHU Minggang LIU Xingmin FANG Yikun LI Zhengbang LI Wei Central Iron & Steel Research Institute Beijing 100081 China Central Iron & Steel Research Institute Beijing 100081 China Central Iron & Steel Research Institute Beijing 100081 China Central Iron & Steel Research Institute Beijing 100081 China Central Iron & Steel Research Institute Beijing 100081 China

magnetic microstructure of high performance Nd-Fe-B magnets was investigated by using magnetic force microscopy. The correlation between magnetic microstructure and coercivity for high performance Nd-Fe-B magnets was studied. It is found that the magnets with different coercivity mechanism take on different microstructures and magnetism. Moreover, the magnetic microstructures of high performance permanent magnets can be explained by the starting field theory model.

关键词： Nd-Fe-B permanent magnets magnetic domains reversal of magnetism starting field theory

Solidification Behavior of Laser Melting Layer of Nd_(15)Fe_(77)B_8 Sintered Magnets and Its Microstructures Evolution

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Journal of Rare Earths 2005年第2期23卷 208-215页

作者：潘晶刘新才 Department of Physics Faculty of Sciences Ningbo University Ningbo 315211 China

To research the solidification behavior and microstructures of a laser remelting/solidification layer on anisotropic Nd_(15)Fe_(77)B_(8 )sintered magnets with their magnetization direction parallel to X, Y, Z-axis respectively, their surfaces (parallel to XOY plane) were scanned by 5 kW Roffin-Sinar 850 type of CO_(2) laser along Y axis. The rapid solidification of the molten alloy in the layer results in three distinct zones. The transition zone close to the unmolten portion of a magnet (substrate), consists of the columnar Nd_(2)Fe_(14)B phase (matrix), the 10.0%~15.1% dendrite primary iron phase dispersing in the matrix, and the Nd-rich phase along Nd_(2)Fe_(14)B grain boundaries. The columnar crystal zone in the middle of the layer consists of the long columnar Nd_(2)Fe_(14)B grains and their grain boundary Nd-rich phase. And the dendrite crystal zone near the free surface of the layer consists of dendrite Nd_(2)Fe_(14)B grains and their grain boundary Nd-rich phase. When the laser scanning velocity is lower, the growing direction of the microstructures in the layer tends to the laser scanning direction step by step. When the velocity is not lower than 25 mm·s^(-1), the laser remelting/solidification layer thins and the columnar crystal zone comprises almost the whole layer. Under this condition, on the substrate with its magnetization direction along X or Y-axis respectively, the columnar Nd_(2)Fe_(14)B grains in the layer grow in the direction of Z-axis (that is their long-axis along Z-axis), their alignment of the easy magnetization axis [001] is parallel to the magnetization direction of the substrate correspondingly; but on the substrate with its magnetization direction along Z-axis, the columnar Nd_(2)Fe_(14)B grains in the transition zone grow at an angle of 30°~50° between Z-axis and their long-axis. And the columnar Nd_(2)Fe_(14)B grains in the columnar crystal zone gradually tend to the Z-axis,and their easy magnetization axis [001] arrange in the rang

关键词： metal materials crystal growth microstructures laser rapid solidification magnetic materials neodymium compounds magnetic domains rare earths

magnetic Microstructures of PryFe90－yB10 （y = 8－11.76） Nanocrystalline Ribbons Using magnetic Force Microscopy ＊

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Chinese Physics Letters 2003年第11期20卷 2033-2035页

作者：庞智勇方以坤张晃伟韩圣浩韩宝善张文成 SchoolofPhysicsandMicroelectronics StateKeyLaboratoryofCrystalMaterialsShandongUniversityJinan250100ShandoneUniversitv.J/nan250100 StateKeyLaboratoryofMagnetism InstituteofPhysicsandCenterforCondensedMatterPhysicsChineseAcademyofSciencesBeijing100080ChineseAcademyofSciencesBeijing100080 DepartmentofPhysics ChungChengUniversityMing-HsiungChia-Yi

magnetic microstructure of melt-spun PryFe90−yB10 (y = 8, 8.5, 9, 9.5, 10 and 11.76) nanocrystalline ribbons in an as-grown state has been studied using a magnetic force microscope. The magnetic domains are characterized by dark areas adjacent to bright areas in a sub-micron scale and in random distribution. By comparing with the size of the micro-crystals measured from the TEM image, the exchange coupling effect was confirmed to exist in all the ribbons. Using the roughness analysis, the variation of the root mean-square values of the phase shifts obtained from the magnetic force images versus the content y of Pr were measured, which is very consistent with the curve of the residual induction Br versus the content y.

关键词： magnetic domains

magnetic texture of Nd_2Fe_(14)B solidified in the surface layer of anisotropic sintered-magnets

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Rare Metals 2006年第Z1期25卷 498-501页

作者： PAN Jing LIU Xincai TU Fenghua Faculty of Materials Science and Chemical Engineering The State Key Laboratory Base of Novel Functional Materials and Preparation Science Ningbo University Ningbo 315211 China Faculty of Materials Science and Chemical Engineering The State Key Laboratory Base of Novel Functional Materials and Preparation Science Ningbo University Ningbo 315211 China Faculty of Materials Science and Chemical Engineering The State Key Laboratory Base of Novel Functional Materials and Preparation Science Ningbo University Ningbo 315211 China

The arrangements of the easy magnetization axis [001] of columnar Nd2Fe14B crystals in the laser scanned layer on anisotropic sintered Nd15Fe77B8 magnets were investigated by XRD and the Bitter method. The results show that the common effects of both the heat flux and the substrate magnetization orientation constrain the columnar Nd2Fe14B solidified from the laser melting pool to form the c-axis texture orientated with the same direction as that of the substrate, when the geometric relationship between the heat flux in the laser scanning layer and c-axis texture orientation of the substrate is perpendicular to each other, and if the laser scanning velocity is no less than 25 mm·min-1. The c-axes of columnar Nd2Fe14B crystals are no longer randomly distributed in the plane normal to their preferential growing direction as they are randomly done in both ingots cooled by water-cooling copper mould and directionally solidified Nd-Fe-B rods.

关键词： c-axis texture magnetic domains Nd2Fe14B laser rapid solidification