Electronic structures and magnetocrystalline anisotropy energies of ordered Co1-xNix alloys: a first principles study

The electronic structures and magnetocrystalline anisotropy (MA) of ordered hexagonal close-packed (hcp) Co1-xNix alloys are studied using the full-potential linear-augmented-plane-wave (FLAPW) method with generalized gradient approximation (GGA). Great changes of magnetocrystalline anisotropy energy (MAE) are gained with different Ni compositions. Also, in-plane magnetocrystalline anisotropy is obtained for Co15Ni in which the Snoek's limit is exceeded. It is found that the changes of the symmetry of the crystal field on Ni induce small variations in band structures around the Fermi level under different compositions, which plays an important role in modulating the magnetization direction, where the hybridization between Co-3d and Ni-3d orbits is of special importance in deciding the magnetocrystalline anisotropy of itinerant states. The rigid-band model is inapplicable to explain the evolution of magnetocrystalline anisotropy energy with Ni composition, and it is also inadequate to predict the magnetocrystalline anisotropy energy through the anisotropy of the orbital magnetic moment.