新半金属材料CrFe2O4的电子结构  

Electronic Structures of New Half-Metal Material CrFe_2O_4

作　　者：刘俊[1,2] 刘宇[1] 陈希明[1] 董会宁[1] 

机构地区：[1]重庆邮电大学应用物理研究所,重庆400065 [2]重庆大学数理学院,重庆400044

出　　处：《物理化学学报》2009年第1期107-112,共6页Acta Physico-Chimica Sinica

基　　金：重庆市自然科学基金(CSTC2007BB4391, CSTC2007BB2448, CSTC2007BB4385, CSTC2008BB4083);重庆市教委科学技术项目(kj060515,kj080518)资助

摘　　要：基于第一性原理,优化了含Cr的高温相尖晶石结构材料(CrxFe1-x)A(CryFe2-y)BO4的几何结构,并对它们的磁电性能进行了计算.基于配位场理论分析了CrFe2O4的电子结构及其具有半金属性的微观机制.计算表明,仅当x=1.0、y=0.0时,(CrxFe1-x)A(CryFe2-y)BO4具有半金属性.CrFe2O4是典型的亚铁磁性耦合的IIB型半金属,其分子磁矩约为5.6μB,大于Fe3O4的4.0μB.在CrFe2O4的四面体晶体场中,中心离子的电子结构可近似写为Cr+t21g0↑t23g↓;八面体晶体场中,中心离子的电子结构可近似写为Fe2+t23g↑0eg2↑t21g↓.CrFe2O4具有半金属性的原因是在配合物ML4和ML6中,中心离子与周围O配体间存在强烈的共价键作用,该作用使中心离子与O配体间形成杂化轨道,导致自旋向上子带被撕裂,进一步使费米面正好处于自旋向上子带带隙中.Geometric structures of cubic spinel materials （CrxFe1-x）A（CryFe2-y）BO4 were optimized and their magnetic and electric properties were calculated using the first principles. Electronic structures and the micromechanism of half-metallicity of CrFe2O4 were analyzed based on coordinate field theory. From our calculation, it is showed that （CrxFe1-x）A（CryFe2-y）BO4 has half-metallicity only when x=1.0 and y=0.0. CrFe2O4 is a type of ferrimagnetic IIB-type halfmetal material and its molecular magnetic moments are about 5.6μB which is higher than the 4.0μB of Fe3O4. Electronic structures of Cr-ions can be approximately written as Cr^＋t2g^1↑t2g^3↓ and those of Fe-ions can be approximately written as Fe^2＋t2g^3↑eg^1↑t2g^1↓. The micromechanism of the half-metallicity of CrFe2O4 is concerned with the strong covalent interaction in the coordinate compounds ML4 and ML6. Mixed orbits between central ions and their ligand result in separated up-spin sub-bands and the Fermi level lies in the gaps of up-spin sub-bands.

关 键 词：自旋电子学 半金属 CrFe2O4 分子磁矩 

分 类 号：O641.1[理学—物理化学]