铁磁性高锰硅化物Mn_4Si_7电子特性的第一性原理计算

First principles calculation of electronic properties of ferromagnetic high manganese silicide Mn_4Si_7

本文采用基于第一性原理的密度泛函理论超软雁势平面波方法,对铁磁性半导体高锰硅化合物Mn_4Si_7进行了理论计算.结果表明块体Mn_4Si_7是准直接带隙半导体材料,其价带主要是由Mn的3d轨道电子构成,导带主要是由Mn的3d及Si的3p轨道电子构成.相同自旋轨道下,自旋向下态的电子更容易占据较高的能级.而自旋向上态的电子对Mn_4Si_7的禁带宽度起主导作用. Mn_4Si_7的费米能级附近各轨道未被电子占满,且自旋向上态与自旋向下态电子的不对称分布使其具有了磁性.为Mn_4Si_7磁学特性提供主要贡献的是Mn的3d轨道电子,而Si的3p和3s轨道电子提供了一个小的贡献.

In this paper, a detailed theoretical study on the ferromagnetic semiconductors Mn4Si7 is performed by using the first-principles plane-wave ultrasoft pseudopotential method based on the density functional theory. The results reveal that Mn4Si7 is a quasidirect bandgap semiconductor. The valence band is mainly composed of the 3 d orbital electron of Mn, while the conduction band is mainly provided by the 3 d orbital electrons of Mn and the 3 p orbital electron of Si. The spin-down electrons, in the same orbit, are more likely to occupy a higher energy level than the spin-up electrons, that play a dominant role in the band gap of Mn4Si7.The orbits near Fermi level are not full, and the asymmetric distribution of electrons makes Mn4Si7 be magnetic. The 3 d orbital electrons of Mn provide a major contribution to the magnetic property of Mn4Si7, while the 3 s and 3 p orbital electrons of Si provide a minor contribution.