物理化学学报 >> 2009, Vol. 25 >> Issue (01): 107-112.doi: 10.3866/PKU.WHXB20090119

研究论文 上一篇    下一篇

新半金属材料CrFe2O4的电子结构

刘俊; 刘宇; 陈希明; 董会宁   

  1. 重庆邮电大学应用物理研究所, 重庆 400065; 重庆大学数理学院, 重庆 400044
  • 收稿日期:2008-07-24 修回日期:2008-10-05 发布日期:2008-12-31
  • 通讯作者: 刘俊 E-mail:liujun@cqupt.edu.cn

Electronic Structures of New Half-Metal Material CrFe2O4

LIU Jun; LIU Yu; CHEN Xi-Ming; DONG Hui-Ning   

  1. Institute of Applied Physics, Chongqing University of Posts and Telecommunications, Chongqing 400065, P. R. China; College of Physics and Mathematics, Chongqing University, Chongqing 400044, P. R. China
  • Received:2008-07-24 Revised:2008-10-05 Published:2008-12-31
  • Contact: LIU Jun E-mail:liujun@cqupt.edu.cn

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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5.6 μB, 大于Fe3O4的4.0 μB. 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+t12g↑t32g↓; 八面体晶体场中, 中心离子的电子结构可近似写为Fe2+t32g↑e2g↑t12g↓. 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.

关键词: 自旋电子学, 半金属, CrFe2O4, 分子磁矩

Abstract: 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 half-metal material and its molecular magnetic moments are about 5.6 μB which is higher than the 4.0 μB of Fe3O4. Electronic structures of Cr-ions can be approximately written as Cr+t12g↑t32g↓ and those of Fe-ions can be approximately written as Fe2+t32g↑e2g↑t12g↓. 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.

Key words: Spintronics, Half-metal, CrFe2O4, Molecular magnetic moments

MSC2000: 

  • O641