Al掺杂对Fe_2Si电子结构和磁学特性的影响

采用第一性原理的贋势平面波方法,计算了无掺杂和Al掺杂Fe_2Si体系的电子结构和磁学特性,并分析了Al掺杂对Fe_2Si体系电磁特性的影响。计算结果表明,未掺杂和Al掺杂Fe_2Si体系为半金属铁磁体,自旋向上的能带结构穿过费米面表现为金属特性,未掺杂Fe_2Si体系自旋向下的能带表现为间接带隙半导体特性,带隙值为0.464 eV;Al掺杂Fe_2Si体系自旋向下的能带表现为Z间的直接带隙半导体特性,带隙值为0.541 eV。Al掺杂使各原子磁矩和Fe_2Si体系的总磁矩均减小,体系的带隙值增加,相应的半金属隙也增加,并且使得体系自旋向下部分由间接带隙变为直接带隙半导体。Fe_2Si体系的半金属性和磁性主要来源于Fe-3d电子之间的d-d交换,Si-3p电子与Fe-3d电子之间的p-d杂化。综上所述,掺杂是调控半金属铁磁体Fe_2Si电磁特性的有效手段。

Effect of Al-doping on the electronic structure and magnetic properties of Fe2Si

The electronic structure and magnetic properties of undoped and Al-doped Fe2Si systems have been calculated by the first-principles pseudo-potential method. The results show that both the undoped and Al-doped Fe2Si systems are half-metallic ferromagnet with metal structure under spin-up. The spin-down band structure of undoped Fe2Si system exhibits an indirect semiconductor characteristic with a band-gap value of 0.464 eV; the Al-doped Fe2Si system exhibits a direct semiconductivity characteristic with a band-gap of 0.541 eV. Al doping decreases the magnetic moment of each atom and the total magnetic moment of Fe2Si system, increases both the band-gap value and increases the corresponding half-metal gap, and also it makes the spin-down parts of the system change from indirect to direct band-gap semiconductors. The half-metallic and magnetic properties of Fe2Si systems are mainly derived from the d-d exchange between Fe-3d electrons, p-d hybridization between Si-3p and Fe-3d electrons. Therefore, doping is an effective mean for regulating the electromagnetic properties of half-metallic ferromagnet Fe2Si.