Dai Y, Zhao Y W, Ma L, Tang M, Qiu X P, Liu Y, Yuan Z, Zhou S M
Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology and Pohl Institute of Solid State Physics and School of Physics Science and Engineering, Tongji University, Shanghai 200092, China.
Center for Advanced Quantum Studies and Department of Physics, Beijing Normal University, Beijing 100875, China.
Phys Rev Lett. 2022 Jun 17;128(24):247202. doi: 10.1103/PhysRevLett.128.247202.
Experimental measurements show that the angular dependence of the anisotropic magnetoresistance (AMR) in L1_{0} ordered FePt epitaxial films on the current orientation and magnetization direction is a superposition of the corresponding dependences of twofold and fourfold symmetries. The twofold AMR exhibits a strong dependence on the current orientation, whereas the fourfold term only depends on the magnetization direction in the crystal and is independent of the current orientation. First-principles calculations reveal that the fourfold AMR arises from the relaxation time anisotropy due to the variation of the density of states near the Fermi energy under rotation of the magnetization. This relaxation time anisotropy is a universal property in ferromagnetic metals and determines other anisotropic physical properties that are observable in experiment.
实验测量表明，L1₀有序FePt外延薄膜中各向异性磁电阻（AMR）对电流取向和磁化方向的角依赖性是二重和四重对称性相应依赖性的叠加。二重AMR对电流取向表现出强烈依赖性，而四重项仅取决于晶体中的磁化方向，与电流取向无关。第一性原理计算表明，四重AMR源于磁化旋转下费米能级附近态密度变化导致的弛豫时间各向异性。这种弛豫时间各向异性是铁磁金属中的普遍特性，并决定了实验中可观测到的其他各向异性物理性质。
