Effect of atomic short-range order on magnetic anisotropy

We present a theory to study the relation between compositional order and m agnetocrystalline anisotropy of ferromagnetic alloys. The ordering phenomen on is represented by static concentration waves. The electronic part is des cribed within the spin-polarized relativistic Korringa-Kohn-Rostoker cohere nt-potential approximation. This scheme can be used to investigate the chan ge in the magnitude as well as the direction of magnetic anisotropy in an a lloy at the onset of ordering. The same framework can also be used to study directional chemical order produced by magnetic annealing. We have calcula ted the magnetocrystalline anisotropy energy of ordered fcc-Co0.5Pt0.5 allo y using this method. We find that the magnetocrystalline anisotropy energy of the ordered phase is two orders of magnitude larger than that of the dis ordered phase. Also, that the direction of 'easy' magnetization in the orde red phase depends on the type of ordering. These results are in good agreem ent with the experimental observations.