Brahimi Samy, Bouzar Hamid, Lounis Samir
Laboratoire de Physique et Chimie Quantique, Université Mouloud Mammeri, Tizi-Ouzou, 15000 Tizi-Ouzou, Algeria.
J Phys Condens Matter. 2016 Dec 14;28(49):496002. doi: 10.1088/0953-8984/28/49/496002. Epub 2016 Oct 18.
The impact of reduced dimensionality on the magnetic properties of the tetragonal L1 CoPt alloy is investigated from ab initio considering several kinds of surface defects. By exploring the dependence of the magnetocrystalline anisotropy energy (MAE) on the thickness of CoPt thin films, we demonstrate the crucial role of the chemical nature of the surface. For instance, Pt-terminated thin films exhibit huge MAEs which can be 1000% larger than those of Co-terminated films. Besides the perfect thin films, we scrutinize the effect of defective surfaces such as stacking faults or anti-sites on the surface layers. Both types of defects reduce considerably the MAE with respect to the one obtained for Pt-terminated thin films. A detailed analysis of the electronic structure of the thin films is provided with a careful comparison to the CoPt bulk case. The behavior of the MAEs is then related to the location of the different virtual bound states utilizing second order perturbation theory.
从第一性原理出发，考虑几种表面缺陷，研究了降维对四方L1型CoPt合金磁性的影响。通过探索磁晶各向异性能量（MAE）对CoPt薄膜厚度的依赖性，我们证明了表面化学性质的关键作用。例如，以Pt为终止层的薄膜表现出巨大的MAE，其值可比以Co为终止层的薄膜大1000%。除了完美薄膜，我们还仔细研究了诸如堆垛层错或反位等缺陷表面对表面层的影响。相对于以Pt为终止层的薄膜所获得的MAE，这两种类型的缺陷都会使其大幅降低。通过与CoPt体相情况进行仔细比较，对薄膜的电子结构进行了详细分析。然后利用二阶微扰理论，将MAE的行为与不同虚拟束缚态的位置联系起来。
