Hwang Yubin, Chung Yong-Chae
Department of Materials Science and Engineering, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul 133-791, Republic of Korea.
J Nanosci Nanotechnol. 2013 Sep;13(9):6316-20. doi: 10.1166/jnn.2013.7727.
Magnetic thin films are expected to be a promising substitute for existing semiconductor materials in the memory device industry due to their stable non-volatility, fast reading/writing speed, and durability. Because of the potential of thin film magnetic materials, Co-Pt alloys have attracted attention for application in magnetic memory devices due to their great magnetic anisotropy energy. In this paper, the stable surface structures of L1(0)-ordered CoPt alloys on a Pt (001) surface according to the thickness of the CoPt thin films was investigated using density functional calculations. The surface phase diagram of the Co-Pt alloys was first obtained to find the most stable surface phases of Co-Pt, and finally the perpendicular A, Pt-rich, perpendicular C and Co-rich B phases were found to be the most stable Co-Pt surface phases considering a thin film thickness from 1 to 4 MLs. Through calculation of the magnetic properties and the analysis of the spin-polarized 3d-electron density of the states of these stable surface phases, the changes in the magnetic properties were found to originate from the change in the relative electron filling in the 3d(x2-y2) and 3d(z2) orbitals of the Co atoms.
由于其稳定的非易失性、快速的读写速度和耐久性，磁性薄膜有望成为存储设备行业中现有半导体材料的一种有前途的替代品。由于薄膜磁性材料的潜力，Co-Pt合金因其巨大的磁各向异性能量而在磁存储设备应用中受到关注。本文利用密度泛函计算研究了Pt(001)表面上L1(0)有序CoPt合金的稳定表面结构随CoPt薄膜厚度的变化。首先获得了Co-Pt合金的表面相图，以找到Co-Pt最稳定的表面相，最后发现，考虑到1至4个单层的薄膜厚度，垂直A相、富Pt垂直C相和富Co B相是Co-Pt最稳定的表面相。通过对这些稳定表面相的磁性计算和自旋极化3d电子态密度分析，发现磁性的变化源于Co原子3d(x2-y2)和3d(z2)轨道中相对电子填充的变化。
