Heusler合金Co2MnAl(100)表面电子结构、磁性和自旋极化的第一性原理研究

基于第一性原理计算方法系统地研究了L2₁和B2结构下的Heusler合金Co₂MnAl(100)表面原子的原子弛豫、电子结构、磁性和自旋极化行为. L2₁和B2结构的Co₂MnAl(100)表面由于Co–Mn和Co–Al的成键差异, 使得不同原子分别发生不同程度的伸缩. 与块体相比, Co和Mn原子的自旋磁矩由于表面效应而明显增大, 电子结构计算显示L2₁结构块体中的带隙被表面态破坏, 表面效应使得两种结构的CoCo端面自旋极化率降低, 但MnAl端面并未受到显著影响, 呈现了较大的自旋极化, 预测其在隧道结中可能具有很好的应用潜力.

First-principles study of the electronic structure,magnetism, and spin-polarization in Heusler alloy Co2MnAl(100) surface

Using the first-principles calculations within the generalized gradient approximation frame work, we systematically investigate the atomic relaxation, electronic structure, magnetism, and spin-polarization in L2₁ and B2 structure of Heusler alloy Co₂MnAl (100) surface. Due to the difference of Co–Mn and Co–Al bonding, surface atoms in the L2₁ and B2 structure prefer to move toward and away from the vacuum. By comparison with the bulk, the spin magnetic moments of surface Co and Mn atoms are obviously enhanced due to the surface effects. Our electronic structure calculations show that the gap in L2₁ structure of bulk Co₂MnAl has been destroyed by the surface states and the spin-polarization of CoCo atomic terminated surface in both structures decreases. However, the spin-polarization of MnAl atomic terminated surface is not significantly affected by the surface effects and has a large value in both structures, and this may be the potential in application to magnetic tunneling junctions.