铁磁/非磁金属异质结中的拓扑霍尔效应  

Topological Hall effect in ferromagnetic/non-ferromagnetic metals heterojunctions

作　　者：孟康康 赵旭鹏[2] 苗君[1] 徐晓光[1] 赵建华[2] 姜勇[1] Meng Kang-Kang;Zhao Xu-Peng;Zhao Jian-Hua;Miao Jun;Xu Xiao-Guang;Jiang Yong(School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China;State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China)

机构地区：[1]北京科技大学材料科学与工程学院,北京100083 [2]中国科学院半导体研究所,北京100083

出　　处：《物理学报》2018年第13期46-55,共10页Acta Physica Sinica

基　　金：国家重点基础研究发展计划(批准号:2015CB921502);国家自然科学基金(批准号:51731003;61404125;51471029;51671019;11574027;51501007;51602022;61674013;51602025)资助的课题~~

摘　　要：在铁磁/非磁金属异质结中,界面处的Dzyaloshinskii-Moriya相互作用会诱导诸如磁性斯格明子等手性磁畴壁结构的形成.当巡游电子通过手性磁畴壁结构时,会获得一个贝里相位,而相应的贝里曲率则等效于一个外磁场,它将诱导额外的霍尔效应,即拓扑霍尔效应.拓扑霍尔效应是当前磁性斯格明子和自旋电子学研究领域的热点之一.本文由实空间贝里相位出发,简要介绍了拓扑霍尔效应的物理机制;然后着重讨论了铁磁/非磁金属异质结中的拓扑霍尔效应,包括磁性多层膜中和MnGa/重金属双层膜中的拓扑霍尔效应.这两种结构都可以通过改变材料的厚度、种类、生长方式等调控界面Dzyaloshinskii-Moriya相互作用,从而有效地调控磁性斯格明子和拓扑霍尔效应.In a magnetic system, the spin orbit coupling can combine with the exchange interaction to generate an anisotropic exchange interaction that favors a chiral arrangement of the magnetization. This is known as the Dzyaloshinskii-Moriya interaction（DMI）. Contrary to the Heisenberg exchange interaction, which leads to collinear alignment of lattice spins,the form of DMI is therefore very often to cant the spins by a small angle. If DMI is strong enough to compete with the Heisenberg exchange interaction and the magnetic anisotropy, it can stabilize chiral domain wall structure such as skyrmion. When a conduction electron passes through a chiral domain wall, the spin of the conduction electron will experience a fictitious magnetic field（Berry curvature） in real space, which deflects the conduction electrons perpendicular to the current direction. Therefore, it will cause an additional contribution to the observed Hall signal that is termed topological Hall effect（THE）. The THE has attracted much attention since it is a promising tool for probing magnetic skyrmions. Recent extensive experiments have focused on the the THE in the ferromagnetic/non-ferromagnetic metal heterojunctions due to the inherent tunability of magnetic interactions in two dimensions. We firstly review the THE in ferromagnetic multilayers, in which the domain wall energy with interfacial DMI can be written as σ = 4（AK）^（1/2）-πD,where Dis the effective DMI energy constant, A the exchange constant, K the anisotropy constant. For the most favorable chirality, it lowers the energy. The limit of this situation is when σ goes to zero, which defines the critical DMI energy constant Dc = 4（AK）^（1/2）/π. Therefore, the domain wall energy would be negative and the chiral domain walls should proliferate if D D_c, and the methods that can modulate D and Dc to reduce σ have been explored. We have also reviewed the THE in Mn Ga/heavy metal bilayers. The largest THE signals have been found based on the Mn Ga films with smallest Dc

关 键 词：斯格明子 自旋轨道耦合 自旋电子学 

分 类 号：O469[理学—凝聚态物理]