Effects of Cu coverage on the magnetic anisotropy of Co/Cu(001)

Using the full-potential linearized augmented plane wave method, the magnetocrystalline anisotropy ~MCA! energies of the Co/Cu~001!, Cu/Co/Cu~001!, and 2Cu/Co/Cu~001! systems are investigated. With the generalized gradient approximation for the exchange-correlation energy/potential, the optimized atomic structures are remarkably improved from those obtained with the local-density approximation. The negative uniaxial MCA energy of Co/Cu~001! (20.61 meV per Co adatom! changes to positive for Cu/Co/Cu~001! ~0.54 meV per Co adatom! and for 2Cu/Co/Cu~001! ~0.21 meV per Co adatom!. This indicates that the Cu overlayers turn the magnetization of Co from the in-plane direction to the perpendicular axis, a conclusion which agrees with experiments. By contrast, the in-plane coefficient of MCA energy appears to be quite stable in these systems.