Key Laboratory of Polar Materials and Devices, Ministry of Education, East China Normal University, Shanghai 200062, People's Republic of China.
J Phys Condens Matter. 2013 Oct 2;25(39):396001. doi: 10.1088/0953-8984/25/39/396001. Epub 2013 Aug 14.
Using first-principles density-functional theory calculations, we systematically investigate the magnetic anisotropy of the multilayer system Cu/(FePt)n/MgO, a promising spintronics structure. Particularly, we have studied the influence of the epitaxial strain, thickness of the ferromagnetic layer, and different interfaces on the magnetic anisotropy energy (MAE) of the system. It is found that the thickness of FePt has slight influence on the MAE, while the increase of the in-plane lattice constant a, or tensile strain, can significantly reduce and even change the sign of the MAE. The calculated density of states shows that the occupation number of the minority spin channel of Fe dx(2)-y(2) orbital decreases with the increase of a, which leads to the reduction of the orbital moment anisotropy of the Fe atom and therefore the decrease of MAE. We also consider the influence of the Cu/FePt and FePt/MgO interfaces on the MAE, and find that both interfaces can reduce the MAE. Especially, the effect of the Cu/FePt interface is more pronounced due to the increased occupation number of the minority spin channel of Fe dz(2) orbital.
使用第一性原理密度泛函理论计算，我们系统地研究了多层系统 Cu/(FePt)n/MgO 的磁各向异性，这是一种有前途的自旋电子结构。特别地，我们研究了外延应变、铁磁层厚度和不同界面对体系磁各向异性能（MAE）的影响。结果表明，FePt 的厚度对 MAE 的影响较小，而面内晶格常数 a 的增加或拉伸应变可显著降低甚至改变 MAE 的符号。计算的态密度表明，Fe dx(2)-y(2)轨道的少数自旋通道的占据数随 a 的增加而减少，这导致 Fe 原子的轨道各向异性矩减小，从而使 MAE 减小。我们还考虑了 Cu/FePt 和 FePt/MgO 界面对 MAE 的影响，发现这两个界面都可以降低 MAE。特别是，Cu/FePt 界面的作用更为显著，这是由于 Fe dz(2)轨道的少数自旋通道的占据数增加所致。
