铁磁态Co基层状氧化物Ca2Co2O5电子状态的研究

Study on Electronic States of Ferromagnetic Co-based Layered Ca_2Co_2O_5 Oxide

采用平面波超软赝势法研究了低自旋状态Co基典型层状氧化物Ca_2Co_2O_5的电子结构。结果表明,层状Co基氧化物Ca_2Co_2O_5呈金属型能带结构,具有明显的各向异性,能带中含有5个子能带,其中费米能附近的能带数量较多,呈较宽的带状分布。自旋向上的电子形成半导体型能带,带隙宽度为0. 37 e V,自旋向下的电子形成金属型能带。系统内部的电子对态密度贡献程度依s,p,d依次增大。Ca的电子形成的态密度对费米能附近的值贡献非常小,Co的d态电子对两层态密度贡献较大,其对系统电性能起着重要作用,且系统Co-O之间存在着较强的相互作用。Ca-Co-O层中的各态电子对态密度的贡献大于Co-O层中的各态电子对态密度的贡献。

The electronic states of the ferroelectric representing Ca 2Co 2O 5 layered oxide was studied by the plane wave as well as the pseodopotential method.The results show that the Ca 2Co 2O 5 layered oxide has metallic type band structure with five sub-bands;the band structure is anisotropic with more bands near Fermi level,and the bands near Fermi level exhibits belt-like distribution.The band structure of the spin up electrons is semiconductor type with indirect band gap of 0.37 eV,however the band structure of the spin down electrons is metallic.The d state electrons contribute to density of states most,the p state electrons contribute to density of state less and the s state electrons contribute to density of state the least.The electrons of Ca contribute to density of state near Fermi level the least.The d state electrons of Co contribute to density of states very much within the two sub-layers,it is important for the system electric properties.There are strong interactions between Co and O within the system.The Ca-Co-O layer contributes to the system density of state more than that of the Co-O layer.