Ab initio theoretical description of the interrelation between magnetocrystalline anisotropy and atomic short-range order

The cubic lattice symmetry of ferromagnetic homogeneously disordered alloys is broken when a compositional modulation is imposed. This can have a prof ound influence on the magnetocrystalline anisotropy energy (MAE). We descri be our ab initio theory of this effect and use the framework of concentrati on waves with the electronic structure described within the spin-polarized relativistic Korringa-Kohn-Rostoker coherent-potential approximation. We fi nd that ordering produces a 2 order of magnitude increase in the MAE as wel l as altering the equilibrium direction of magnetization. Using the same th eoretical framework we also examine directional compositional order produce d by magnetic annealing with an explicit study of permalloy.