First-principles calculations of the magnetic anisotropic constants of Co-Pd multilayers: Effect of stacking faults

Using first-principles density functional theory calculations with spin-orbit coupling, we systematically investigate the magnetic anisotropic energy (MAE) of Co _nPd _m (n+m=5) magnetic multilayers. We consider the influences of the relative atomic weight of Co, w _Co, stacking fault, and external stress on the MAE. We find that out-of-plane lattice constant, saturation magnetization, and magnetic moments are almost linearly correlated with w _Co. The magnetic anisotropic constant (MAC) curve of Co _nPd _m without stacking fault shows a near-linear dependence on w _Co that agrees with our derived effective MAC K _u ^eff which includes shape, magneto-crystalline, and magneto-elastic contributions. We also show that the contributions from Pd layers to both the total magnetic moments and magnetic anisotropy are significant. The stress anisotropy due to the substrate has a weak effect on the MAC. However the stacking fault has a strong effect on the MAC. When the Co layer is thin, a Co-Pd interface without stacking fault is necessary for higher K _u ^eff. However, when the Co layer is thick, creating stacking faults inside the Co region may produce a larger K _u ^eff. Our study suggests the ways to increase the perpendicular magnetic anisotropy in Co-Pd multilayer systems and subsequently leads to the development of novel magnetic recording devices.