F掺杂四方钙钛矿结构BiFeO_3的铁磁性和电子结构第一性原理研究

First Principle Study on Ferromagnetic and Electronic Structure of Tetragonal Perovskite BiFeO_3 with F Doped

采用第一性原理方法,研究了F掺杂四方钙钛矿结构BiFeO_3(T-BiFeO_3)的铁磁性和电子结构。基于TBiFeO_3的四种磁结构,本文计算了两种可能的掺杂位置,确定了最稳定的T-BiFeO_(3-x)F_x结构。研究发现,不同F的浓度对T-BiFeO_3的总磁矩影响不同,当掺杂为T-BiFeO_(2.75)F_(0.25)时,其总磁矩最大,为2μB。进一步分析发现,TBiFeO_(3-x)F_x的总磁矩主要来源于F原子及其最近邻的Fe原子。电子结构分析表明,费米能级附近的杂质态主要是掺杂后Fe 3d轨道和O 2p轨道向高能级移动而形成的。另外,T-BiFeO_(2.75)F_(0.25)具有比较大的极化强度。

The ferromagnetic property and electronic structure of tetragonal perovskite BiFeO 3 (T-BiFeO 3) were investigated. Considering two possible doping sites of T-BiFeO 3, the most stable structure of T-BiFeO 3 was obtained based on four magnetic structures of T-BiFeO 3. It is found that the total magnetic moment of T-BiFeO 3 with F doped is different with the difference of F concentration. The T-BiFeO 2.75 O 0.25 has the maximum magnetic moment (2 μB) with the increase of F concentration. The total magnetic moment of T-BiFeO 3- x F x with F doped are mainly coming from the Fe atom and O atoms nearly F after F replacing O. Furthermore, it shows that the impurity states around Fermi are mainly derived from Fe 3d and O 2p orbitals. In addition, the T-BiFeO 2.75 O 0.25 has also larger polarization.