W形六角铁氧体BaFe_(18)O_(27)电子结构与导电性的第一性原理研究  

First-principles study of the electronic structure and electric conductivity in W-type hexagonal ferrite BaFe_(18)O_(27)

作　　者：李忠虎[1,2] 李林[1] 朱林[1] 

机构地区：[1]东北大学理学院物理系,沈阳110819 [2]朝鲜理科大学物理系

出　　处：《物理学报》2011年第10期542-548,共7页Acta Physica Sinica

基　　金：辽宁省计划科学基金(批准号:2006222002)资助的课题~~

摘　　要：采用基于第一性原理的GGA+U方法研究了BaFe18O27的晶体结构和基态电子结构.以实验数据为初始结构的离子弛豫显示,由于稳定结构中离子半径的差异和2d位Fe的存在,位于BaO层中6h位的O离子脱离了实验结构中原胞的"表面"位置,产生畸变.计算得到晶体磁矩为28μB/f.u.,与实验相符.电子态密度及能带计算表明该材料具有微弱的半金属特性,而且与c轴平行方向和垂直方向的能带色散关系有着很大不同,6g位Fe在该材料的输运特性中起着关键作用,它们形成一种"导电层",导致垂直电导率和平行电导率出现非常大的差异.The electronic ground state and the electric conductivity of W-type hexagonal ferrite BaFe18O27 are investigated in the generalized gradient approximation（GGA） as well as the GGA plus Hubbard U（GGA＋U） scheme.The ionic relaxation calculation of the experimental crystal structure shows that oxygen ions at 6h site in the BaO layer move away from the ＂surface＂ position in the unit cell,resulting in a structural distortion.The magnetic moment of the cell is calculated to be 28 μB/f.u.,in agreement with previous experimental results.By taking account of electronic band structure and crystal ionic configuration it is found that the material is a weak half-metal and the effective mass of conduction electrons along the c axis is much heavier than that perpendicular to this axis.Fe ions on octahedral 6 g sites and O ions around them of the spinel block form a ＂conductive layer＂.Therefore the electric conductivity perpendicular to the c axis is much greater than that parallel to the c axis.

关 键 词：第一性原理 W形六角铁氧体 电子结构 导电性 

分 类 号：TM277[一般工业技术—材料科学与工程]