六方Fe2Ge合金块体及其(001)表面电子结构和磁性的第一性原理

采用基于密度泛函理论第一性原理的赝势平面波方法,计算了块体Fe₂Ge及其(001)表面的电子结构和磁性。考虑了两种类型的终端(001)表面:Ge(Ⅰ)-(001)表面和Ge(Ⅱ)-(001)表面。电子结构方面,不同类型的Fe₂Ge(001)表面都表现出金属特性,这与块体的金属性保持一致。通过计算它们的自旋极化率,得出Ge(Ⅰ)-(001)表面的自旋极化程度最高。磁性方面,在块体和Ge(Ⅱ)-(001)表面的Ge原子是铁磁自旋有序的,而在Ge(Ⅰ)-(001)表面第一层的Ge原子是亚铁磁自旋有序的。此外,Ge(Ⅱ)-(001)表面Ge原子的自旋磁矩优于块体中和Ge(Ⅰ)-(001)表面Ge原子的自旋磁矩。这些结果与Fe的d态和Ge的p态电子的杂化有关,本文中通过分析它们的态密度进行了讨论。

First-Principle Study on Electronic Structure and Magnetic Properties of Bulk and Its (001) Surfaces of Hexagonal Fe2Ge Alloy

The electronic structures and magnetic properties of the bulk Fe₂Ge and its (001) surfaces were calculated by the pseudo-potential plane wave method based on the first-principle of density functional theory. Here, two types of the terminated (001) surfaces were considered: Ge(Ⅰ)-(001) surface and Ge(Ⅱ)-(001) surface. For the electronic structures, the different types of the Fe₂Ge (001) surfaces all show metallic characteristics, which are in agreement with the bulk counterpart. For the magnetism, the Ge atoms are ferromagnetic spin ordering in the bulk and Ge(Ⅱ)-(001) surface, while the Ge atoms are ferrimagnetic spin ordering in the first layer of the Ge(Ⅰ)-(001) surface. Moreover, the spin magnetic moment of the Ge atoms in the Ge(Ⅱ)-(001) surface are better than those of the bulk and Ge(Ⅰ)-(001) surface. These results are related to the hybridization between the Fe d and Ge p states, which were discussed by analyzing their density of states.