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) (-0.61 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. [S0163-1829(99)03737-6].