Magnetic Anisotropy and Damping for Monolayer-Controlled Co | Ni Epitaxial Multilayer

Structures and magnetic properties were systematically investigated for the monolayer (ML)-controlled Co | Ni multilayers with various Ni layer thicknesses, where the Co and Ni layers were epitaxially grown on a Al2O3 (\(112̄0\)) single crystal substrate or deposited on a thermally oxidized Si substrate. The epitaxial Co | Ni multilayers exhibited high uniaxial magnetic anisotropy energies (Ku) and low effective magnetic damping constants (αeff), resulting in the perpendicular magnetization with low damping even for the 1 ML-Ni | 1 ML-Co multilayer. By comparing the experimental results with the first principles calculation, we found that the Ni atoms largely contributed to the perpendicular anisotropy for the Co | Ni multilayers. We also discussed the possible mechanism dominating the magnitude of αeff for the Co | Ni multilayers based on the experiments and the calculations. The present results suggest that the epitaxial Co | Ni multilayer is a promising material to achieve high Ku and low magnetic damping simultaneously.