双交换作用下Li_(1±y)(Mg_(1-x)Cr_(x))As的半金属铁磁性  

Half metallic ferromagnetism of Li_(1±y)(Mg_(1-x)Cr_(x))As withdouble exchange interaction

作　　者：罗一瑛 张伟华 冉沛林 丁守兵 毋志民 LUO Yiying;ZHANG Weihua;RAN Peilin;DING Shoubing;WU Zhimin(Chongqing Key Laboratory of Photoelectric Functional Materials,College of Physics andElectronic Engineering,Chongqing Normal University,Chongqing 401331,China)

机构地区：[1]重庆师范大学物理与电子工程学院,光电功能材料重庆市重点实验室,重庆401331

出　　处：《功能材料》2023年第11期11139-11146,11176,共9页Journal of Functional Materials

基　　金：重庆市教育委员会科学技术研究项目(KJQN202200511);重庆市自然科学基金面上项目(cstc2019jcyj-msxmX0251);重庆市博士直通车项目(CSTB2022BSXM-JCX0092)。

摘　　要：采用基于密度泛函理论的第一性原理方法,计算并分析了96原子Li_(1±y)(Mg_(1-x)Cr_(x))As体系的铁磁稳定性、电子结构、自旋电荷密度、投影态密度和差分电荷密度。结果表明,Cr的掺杂引入了自旋极化杂质带,形成了强于Mg-As的Cr-As共价键,体系表现出强的半金属性,产生7.03μB的净磁矩。体系的磁电性质还受到Li计量数的调控,减少Li含量使Cr-As间的共用电子对偏移程度略微增大,Cr-3d与As-4p的p-d杂化有所减弱,净磁矩减小为6.14μB;Li1.03125(Mg_(0.9375)Cr_(0.0625))As发生sp-d杂化,材料转变为n型掺杂,半金属能隙减小为0.375 eV,具有最大的净磁矩7.61μB。通过分析自旋电荷密度和Cr-3d轨道的投影态密度发现,体系的铁磁耦合起源于Cr离子间的双交换作用。As^(3-)作为桥梁形成Cr_(1)-As-Cr_(2)链,巡游d电子在Cr_(1)-As-Cr_(2)链间的跃迁导致Li_(1±y)(Mg_(1-x)Cr_(x))As中的两个Cr离子均具有平行磁矩,从而使体系具有稳定的铁磁性。In this paper,using the first-principles calculation based on density functional theory,we calculated and analyzed the ferromagnetic stability,electronic structure,spin charge density and differential charge density of 96 atom Li_(1±y)(Mg_(1-x)Cr_(x))As.The results showed that the spin polarized impurity band was introduced by Cr doping,Cr doped into the system created Cr-As covalent bonds that were stronger than Mg-As bonds.The system showed strong half-metallicity and had 7.03μB magnetic moment.The properties of Li_(1±y)(Mg_(1-x)Cr_(x))As were also controlled by the stoichiometry of Li,for Li 0.96875(Mg_(0.9375)Cr_(0.0625))As,the deviation of the share electron was enhanced slightly,the results revealed that p-d hybridization happened in Cr-3 d and As-4 p,and the hybridization weakened slightly,the magnetic moment decreased slightly to 6.14μB;In Li_(1).03125(Mg_(0.9375)Cr_(0.0625))As,the sp-d hybridization was occurred,and had the maximum net magnetic moment of 7.61μB,the minimum half-metallic band gap was 0.375 eV,the system still showed strong half-metallicity,the material transformed to n-type doping.The ferromagnetic coupling of the Li_(1±y)(Mg_(1-x)Cr_(x))As can be attributed to the double exchange interaction,the hopping of itinerant d electrons between the Cr_(1)-As-Cr_(2)chains resulted in two Cr ions of Li_(1±y)(Mg_(1-x)Cr_(x))As having parallel magnetic moments,thus giving the system a stable ferromagnetism.

关 键 词：Li_(1±y)(Mg_(1-x)Cr_(x))As 第一性原理 双交换作用 半金属铁磁性 

分 类 号：O469[理学—凝聚态物理] O472[理学—电子物理学]