Ferromagnetic Anisotropy Energies of Co Metal and Co Alloys –Band Model–

The ferromagnetic anisotropy energy of H. C. P. Co metal is calculated by the use of the energy bands of ferromagnetic Co metal given by Ishida. The doubly degenerate energy levels along [0001] axis on the Brillouin zone produce the contributions to make c -axis to be the easy axis. The other doubly degenerate energy levels and the approaching energy levels produce the contributions to make c -plane to be the easy direction. It is shown that at 0 K, c -axis is the easy axis, and when the temperature is raised and the exchange splitting decreases, c -plane becomes the easy direction. The anisotropy energies of Co alloys including 1 at% of Fe and Ni metal are also calculated. The obtained results are in agreement with the experimental results.