休斯勒合金Mn_(2)LiGe块体和(001)表面的电子结构和磁性质  

Electronic Structure and Magnetic Properties of the Bulk and (001) Surface of Heusler Alloy Mn_(2)LiGe

作　　者：孙亮 张钰 王群 SUN Liang;ZHANG Yu;WANG Qun(School of Physics and Electronic Engineering,Jiangsu Normal University,Xuzhou 221000,China;CW CHU College,Jiangsu Normal University,Xuzhou 221000,China)

机构地区：[1]江苏师范大学物理与电子工程学院,徐州221000 [2]江苏师范大学敬文书院,徐州221000

出　　处：《人工晶体学报》2024年第8期1378-1385,共8页Journal of Synthetic Crystals

基　　金：大学生创新创业训练计划(XSJCX14169)。

摘　　要：基于密度泛函理论的第一性原理计算,本文研究了休斯勒合金Mn_(2)LiGe块体及其(001)表面的电子结构和磁性质。对于Mn_(2)LiGe块体,其基态结构是具有反铁磁排布且空间群为F43m的反Heusler合金,晶格常数为5.87A。自旋向下通道费米面附近具有一个宽度为1.1 eV的直接带隙。晶格常数在5.55~6.33A时,Mn_(2)LiGe块体均具有半金属性和稳定的磁性。此外,本文构建了6种不同的表面结构,表面第一层原子经历了不同的位移,增加了表面粗糙度。由于表面效应,表面原子磁性与块体中相比亦有所不同。Mn^(A)Mn^(A)和Mn^(B)Mn^(B)表面结构具有最高的磁矩值,而LiLi和GeGe表面结构的磁矩最低。电子结构计算表明,块体中存在的半金属带隙在6种表面结构中均被破坏,自旋极化率受到不同程度的削弱。只有LiLi表面结构保持高达99.9%的表面自旋极化率,因此该表面在自旋电子学器件中具有良好的应用前景。Using first-principles calculations based on density-functional theory,this paper investigates the electronic structure and magnetic properties of the Heusler alloy Mn_(2) LiGe bulk and its(001) surfaces.The Mn_(2) LiGe bulk is demonstrated to be inverse Heusler alloy with space group of F43m and lattice constant of 5.87A.A direct band gap with a width of 1.1 eV near the Fermi surface of the spin-down channel is detected.The Mn_(2) LiGe bulk possesses stable half-metallic and magnetism in the lattice constant range of 5.55~6.33 A.In addition,six different surface structures of Mn_(2)LiGe are constructed in this paper.The first layer atoms on the surface undergo different displacements,increasing the surface roughness.Due to surface effects,the magnetic properties of atoms on the surface are different compared to those in the bulk.Both the Mn^(A)Mn^(A) and Mn^(B)Mn^(B) surface structures have the highest magnetic moments,while the LiLi and the GeGe surface structures have the lowest magnetic moments.Electronic structure calculations show that the half-metallic band gap present in the bulk is destroyed in all six surface structures and the spin polarization is weakened in varying degrees.Only the LiLi surface structure maintains up to 99.9% of the surface spin polarization,making the surface an excellent prospect for applications in spintronic devices.

关 键 词：第一性原理 休斯勒合金 表面 电子结构 磁性质 自旋极化率 

分 类 号：O469[理学—凝聚态物理]