First-principles study on magnetocrystalline anisotropy of cobalt films: hcp vs fcc

In this study, density functional calculations are performed on magnetocrystalline anisotropy (MCA) of hcp and fcc Co films to reveal influence of symmetry, thickness, and surface. First, MCA of bulk is revisited. MCA energy (E-MCA) of hcp is 15.61 mu eV/atom, two orders of magnitude larger than 0.53 mu eV/atom of fcc Co. Smaller E-MCA of fcc Co originates from the negative contributions from the highly peaked unoccupied minority |m| = 1 states at Fermi level (E-F). In Co films, E-MCA is significantly enhanced to 175.90 and 211.48 mu eV/atom at both hcp and fcc surfaces, resulting in the same order of magnitude for both the films. Substantial E-MCA enhancement stems from the increased occupied and unoccupied minority |m| = 2 states located very close to E-F. Strong E-MCA oscillation with thickness is observed for less than 10 monolayers, whose origin comes from the quantum well |m| = 1 states at E-F.

Automated summary

In this study, density functional calculations were used to investigate the magnetocrystalline anisotropy (MCA) of hcp and fcc Co films. The results reveal that symmetry, thickness, and surface have significant effects on the MCA of the films. The MCA energy of Co films is greatly enhanced compared to bulk, and thickness-dependent oscillations in MCA were observed.