基于第一性原理的Mn-AlN和Cr-AlN的半金属性质

Half-Metallic Properties of Mn-AlN and Cr-AlN Based on First-Principles

基于密度泛函理论(DFT)的第一性原理方法,在广义梯度近似(GGA)下研究了纤锌矿Mn-AlN和Cr-AlN的能带结构、态密度与磁学等性质.结果表明,Mn-AlN和Cr-AlN的半金属能隙都随着杂质浓度的增大而减小.原因可能是随着Mn/Cr掺杂浓度的增大,杂质原子间相互作用增强,Mn/Cr 3d与N 2p杂化减弱,使得自旋交换劈裂变小,从而半金属能隙变窄.在同等掺杂浓度下,Mn-AlN比Cr-AlN的半金属能隙大.这是因为Mn 3d态能级比Cr 3d态能级低,Mn 3d与N 2p杂化更强,导致自旋交换劈裂更大,自旋向下子带的导带底相对远离费米能级,因此Mn-AlN的半金属能隙较大.

The band structures,density of states（DOS）,and magnetic properties of wurtzite Mn-AlN and Cr-AlN were studied using density functional theory（DFT） with the generalized gradient approximation（GGA） for the exchange-correlation potential.The results indicate that the half-metallic gap of Mn-AlN and Cr-AlN decreases as the Mn/Cr doping concentration increases.This probably results from an increase in the interaction between Mn and Mn or Cr and Cr atoms and a decrease in the hybridization of Mn/Cr 3d and N 2p states with increasing the Mn/Cr doping concentration,which results in a smaller spin-exchange splitting so the half-metallic gap is reduced.Additionally,with the same doping concentration,the half-metallic gap of Mn-AlN is larger than that of Cr-AlN.This is due to the lower Mn 3d states compared to the Cr 3d states and the hybridization of Mn 3d and N 2p states being stronger in Mn-AlN,which leads to a larger spin-exchange splitting so the conduction band minimum of the down spin bands moves far away from the Fermi level and the half-metallic gap of Mn-AlN becomes larger.