Calculated magnetocrystalline anisotropy of a FePd ordered alloy: Electron-density dependence on the direction of magnetization

The magnetocrystalline anisotropy energy of a CuAu(I) Fe₅₀Pd₅₀ alloy has been calculated by using a full potential linear augmented planar wave (FLAPW) method. The tetragonal unit-cell distances have been extracted from the x-ray data of ordered FePd films grown by sputtering technique [P. Caro, A. Cebollada, D. Ravelosona, F. Briones, D. García, M. Vázquez, and A. Hernando, J. Appl. Phys. 81, 5050 (1997)]. This ordered alloy presents a high uniaxial magnetic anisotropy with an easy magnetization direction oriented along the tetragonal axis (c axis) of its unit cell. We reproduce the measured uniaxial character as well as the magnitude of its magnetic anisotropy. Three ground-state configurations have been calculated attending to the direction of the magnetization relative to the c axis: 0°, 45°, and 90°. The comparison among these states enables us to describe the changes of the electronic density associated to the changes of the direction of the magnetization.