铁磁性高锰硅化物Mn_4Si_7电子特性的第一性原理计算

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.

First principles calculation of electronic properties of ferromagnetic high manganese silicide Mn4Si7

In this paper, a dedailed theoretical study on the ferromagnetic semiconductors Mn4Si7 is performed by using the first-principles ultrasoft seudopotential method based on the density functional theory. The results shows that Mn4Si7 is a direct bandgap semiconductor. The valence band is mainly composed of the 3d state electron of Mn, while the conduction band is mainly provided by the 3d orbital electron of Mn and the 3p 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, while spin upwards electrons play a dominant role in the band gap of Mn4Si7. The orbits near Fermi level are not full, and the asymmetric distribution of spin up and down electrons makes Mn4Si7 magnetic. The main contribution of the magnetic moment of Mn4Si7 is provided by the 3d orbital electron of Mn, while the 3s and 3d orbital electrons of Si provide a small contribution.