Effect of Topological Bumpy Surface Underlayer on Compositionally Modulated Atomic Layer Stacking in High K_u hcp Co₈₀Pt₂₀ Film With (00.2) Crystallographic Texture Orientation

The effect of topological bumpy surface underlayer on compositionally modulated atomic layer stacking in high uniaxial magnetocrystalline anisotropy (K_u) hcp Co₈₀Pt₂₀ film with (00.2) crystallographic texture orientation was investigated. In this paper, the following has been discussed. Concerning preparation of underlayer with various morphologies, an annealing process prior to the deposition of Co₈₀Pt₂₀ film, and introduction of a metal-oxide buffer layer are effective to obtain underlayers with surface roughness ranging from ∼0.4 to 2 nm and grain size ranging from ∼6.7 to 12.5 nm. To realize a compositionally modulated atomic layer stacking structure, which is confirmed by the high angle annular dark field detector scanning transmission electron microscopy observation, an underlayer with surface roughness less than ∼1 nm and/or grain size larger than ∼8 nm is required. The compositional modulation shows the same normal direction as substrate normal and the c-axis direction of the hcp grain. To reach K_u of ∼1.7 × 10⁷ erg/cm³, surface roughness reduction to ∼0.5 nm and grain size increase to ∼12 nm are needed.