四元Heusler合金Co_2[Mn,Fe]Ge_(1-x)Ga_x的晶体结构、半金属稳定性和磁性

The Structure,Half-metallic Stability and Magnetic Moment of Quaternary Heusler Alloys Co_2Ge_(1-x)Ga_x

基于密度泛函理论的第一性原理研究了四元Heusler合金Co2MnGe1-xGax和Co2FeGe1-xGax的晶体结构、半金属稳定性和磁性,发现随着掺入Ga比例x的改变,其晶格常数遵循Vigard原理。对于Co2MnGa1-xGex系列的合金,其原胞磁矩很好地符合SP(Slater-Pauling)值和实验值;而对于Co2MnGe1-xGax系列合金,其原胞磁矩虽然与实验值一致,但却随x的减小而逐渐偏离SP值。态密度显示,Co2MnGe1-xGax系列合金在x=0～0.75的掺杂比例内都有0.4～0.6eV的自旋向下带带隙宽度,而Co2FeGe1-xGax虽然在费米面附近也存在较高的自旋极化,但几乎不存在显著的自旋向下带带隙。此外,四元合金Co2MnGe0.75Ga0.25的费米面居于最小自旋带隙的中部,将具有较好的半金属稳定性。

Using first-principle within density functional theory （DFT）, the structure, half-metallic stability and magnetic moment of quaternary Heusler alloys Co2 [Mn, Fe]Ge1-xGax were investigated. The results present that with the change of doped Ga contents x, their lattice constants follow Vigard law. In the case of Co2 MnGe1-xGax series, the calculational total cell magnetic moments（TCMM） are well consistent with Slater-Pauling（SP） principle and experimental values, while for Co2 FeGe1-x Gax series, their TCMMs are compatible with experimental values, but deviation from SP values gradually increase with x. Density of states （DOS） show that range from x=0 to 0. 75, a 0. 4-0. 6eV minority-spin energy gaps （MEG） exist in Co2 MnGe1-xGax series, while in Co2 FeGe1-x Ga, series, the high spin polarizability also appears near by Fermi energy, but distinct minority-spin energy gap hasn＇t been found. Furthermore, the Fermi energy of quaternary alloy Co2 MnG0. 75 Ga0. 25 locates at the middle of MEG, and exhibits excellent half-metallic stability.