Heusler合金Mn2NiGe马氏体相变的带Jahn-Teller效应研究  

A band Jahn-Teller effect in the martensitic phase transition of the Heusler alloy Mn_2NiGe

作　　者：罗礼进[1] 仲崇贵[1] 董正超[1] 方靖淮[1] 周朋霞[1] 江学范[2] 

机构地区：[1]南通大学理学院,南通226007 [2]常熟理工学院,江苏省新型功能材料重点建设实验室,常熟215500

出　　处：《物理学报》2012年第20期460-465,共6页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:10974104,30970754,11174043)资助的课题~~

摘　　要：运用第一性原理的方法,计算磁性形状记忆合金Mn_2NiGe的晶体结构、磁结构、电子结构在马氏体相变中的变化.结果表明:Mn_2NiGe在发生马氏体相变时,产生了c轴拉长而a和b轴缩短的Jahn-Teller畸变,形成一个由两根长键和四根短键组成的拉长的八面体;伴随Jahn-Teller畸变,处于八面体中心的Mn离子的磁矩发生了显著的变化,而作为配体的Ni和Ge离子的磁矩基本不变;Jahn-Teller效应中Mn离子的e_g和t_(2g)能级的分裂,源自于晶体畸变所产生的配位场的改变,导致Mn离子d电子态密度的重新分布,从而在费米能级两侧打开一个赝能隙.The changes of crystal structure, magnetic structure, electronic structure in the martensitic phase transition for magnetic shape memory alloy Mn2NiGe are calculated by first-principles method. The results show that in the martensitic phase transition for Mn2NiGe, there is produced a Jahn-Teller distortion, in which the c-axis becomes longer but a-axis and b-axis turn shorter, form- ing an elongated octahedral geometry. There is a significant change in magnetic moment for Mn ion in the centre of octahedron, but a little change happens to the Ni and Ge ions that are regarded as a ligand. The energy levels of eg and t2g are split by redistributing the density of states for d electrons and so opening a pseudogap near the fermi energy due to lattice distortion.

关 键 词：Mn2NiGe 马氏体相变 带Jahn.Teller效应 第一性原理 

分 类 号：TG139.6[一般工业技术—材料科学与工程]