第一性原理研究half-Heusler合金VLiBi和CrLiBi的半金属铁磁性  

First-principles study on half-metallic ferromagnetism of half-Heusler alloys VLiBi and CrLiBi

作　　者：姚仲瑜[1] 孙丽[1] 潘孟美[1] 孙书娟[1] 刘汉军[1] Yao Zhong-Yu;Sun Li;Pan Meng-Mei;Sun Shu-Juan;Liu Han-Jun(School of Physics and Electronic Engineering,Hainan Normal University,Haikou 571158,China)

机构地区：[1]海南师范大学物理与电子工程学院,海口571158

出　　处：《物理学报》2018年第21期325-333,共9页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:11364014)资助的课题~~

摘　　要：构建只含有一种过渡金属元素的half-Heusler合金VLiBi和CrLiBi.采用第一性原理的全势能线性缀加平面波方法计算half-Heusler合金VLiBi和CrLiBi的电子结构.计算结果表明, VLiBi和CrLiBi是半金属性铁磁体,它们的半金属隙分别是0.25 eV和0.46 eV,晶胞总磁矩分别为3.00μB和4.00μB.磁性计算结果显示,晶胞总磁矩主要来源于V和Cr的原子磁矩, Li和Bi的原子磁矩较弱,而且Bi的原子磁矩为负值.利用平均场近似方法计算合金的居里温度TC, VLiBi和CrLiBi的居里温度(TC)的估算值分别为1401 K和1551 K.使晶格常数在±10%的范围内变化,分别计算VLiBi和CrLiBi的电子结构.计算研究表明,晶格常数在-5.6%—10%和-6.9%—10%的范围内变化时VLiBi和CrLiBi仍具有半金属性,并且晶胞总磁矩稳定于3.00μB和4.00μB.采用局域密度近似(LDA)+U (电子库仑相互作用项)的方法计算VLiBi和CrLiBi的电子结构,当U的取值增大到5 eV时VLiBi和CrLiBi仍保持半金属性.此外,采用考虑自旋-轨道耦合(spin-orbit coupling, SOC)效应的广义梯度近似(GGA)+SOC方法计算VLiBi和CrLiBi的电子结构,计算结果显示有微弱的自旋向下能带穿过费米能级,此时VLiBi和CrLiBi在费米面处的自旋极化率分别为98.8%和94.3%,它们的晶胞总磁矩分别为3.03μB和4.04μB. VLiBi的半金属性几乎不受SOC效应的影响,而CrLiBi在费米面处仍有较高的自旋极化率.The hypothetical half-Heusler alloys VLiBi and CrLiBi containing only one transition metal element are constructed.The electronic structure and magnetic properties of VLiBi and CrLiBi are investigated by using the first-principles fullpotential linearized augmented plane wave method based on density functional theory. The spin-polarized calculations of electronic structure for the half-Heusler alloys VLiBi and CrLiBi are performed. The calculation results reveal that VLiBi and CrLiBi are half-metallic ferromagnets with the half-metallic gaps of 0.25 eV and 0.46 eV and the total magnetic moments of 3.00 μB and 4.00 μB per formula unit, respectively. The total magnetic moments mainly originate from the magnetic moment on V or Cr atom. Li and Bi have small atomic magnetic moments, where the atomic magnetic moment of Bi is negative. The mean field approximation method is used to estimate the Curie temperatures of the alloys. The calculated results show that the values of Curie temperature for VLiBi and CrLiBi are 1401 K and 1551 K, respectively.To study the robustness of the half-metallicity with the change of lattice constant, the electronic structures of VLiBi and CrLiBi are also calculated under their lattice constant changing from -10% to ＋10% relative to the equilibrium lattice constant. It is found that the VLiBi and CrLiBi can maintain their half-metallicity and retain their total magnetic moments of 3.00 μB and 4.00 μB per formula unit even when their lattice constants change from -5.6% to 10.0% and from -6.9% to 10.0%, respectively. To discuss the effect of strongly correlated interaction on the half-metallicity, the electronic structure of VLiBi and CrLiBi are calculated by the LDA＋U method with U for V-3 d and Cr-3 d orbital. The calculation results indicate that VLiBi and CrLiBi can keep their half-metallicity and integer total magnetic moments of 3.00 μB and 4.00 μB when the value of U reaches to 5 eV. Also, the electronic structure of VLiBi and CrLiBi are recalculated by the GGA＋SOC method.

关 键 词：半金属 第一性原理 电子结构 铁磁性 

分 类 号：O469[理学—凝聚态物理]