Cr含量对ZB型半金属铁磁体Cr_xZn_(1-x)Se磁电性能的影响

Influence of the Cr-content on the magnetic and electric properties of ZB half-metallic ferromagnets Cr_xZn_(1-x)Se

使用基于密度泛函理论的第一性原理方法,优化了闪锌矿结构的Cr_xZn_(1-x)Se(x=0.000,0.125,0.250和0.375)的2×2×2超胞的几何结构,计算了其自旋极化的态密度和能带结构、离子磁矩、电荷分布等磁电性能,详细分析了Cr含量对Cr_xZn_(1-x)Se磁电性能的影响.结果表明,Cr掺杂后ZB型ZnSe具有明显的半金属特性;当x=0.125,0.250和0.375时,Cr_xZn_(1-x)Se均有较宽的半金属带隙,从而可能具有较高的居里温度;当x=0.125时,Cr_xZn_(1-x)Se的半金属性最稳定;x=0.125,0.250和0.375时,Cr_xZn_(1-x)Se的超胞磁矩分别为整数磁矩4.0,8.0和12.0μ_B,而具有整数磁矩是半金属铁磁体非常重要的特征之一.Cr_xZn_(1-x)Se的半金属性和磁性主要来源于Cr离子的自旋极化,Cr离子的电子结构为Cr e_g^2↑e_g^1↓t_(2g)~3↑.

The geometrical structures of 2×2×2 CrxZn1-xSe （x=0. 000, 0. 125, 0. 250 and 0. 375） supercells were optimized based on the density functional theory. Then their magnetic and electric properties, including the spin-polarized state densities and band structures, the ionic magnetic moments and the charge distribution were calculated and analyzed systematically. The infulence of Cr-content on the electric and magnetic properties of the half-metallic ferrimagnets were analyzed. Results show that the Cr-doped ZB CrxZn1-xSe have evident half-metallicity. CrxZn1-xSe （x=0. 125, 0. 250 and 0. 375） have wide half-metallic band gaps, then potentially have high Curie temperatures. The half-metallicity of CrxZn1-x Se is most stable if x = 0. 250. The supercell magnetic moments of CrxZn1-x Se （x = 0. 125, 0. 250 and 0. 375） are 4. 0, 8.0 and 12.0 μB, respectively. These supercell magnetic moments are integral. Having inetegral mangetic moments is one of important half--metallic characters of materials. The half-mataillicity and supercell magnetic moments mainly come from spin-polarization of Cr-ions. The electronic structures of Cr-ions are Cr Cre8^2↑e8^2↓t2g^3↑.