Spin and orbital magnetism in Fe-Co and Co-Ni alloys

Using the linear muffin-tin orbital method and the virtual-crystal approximation, we have calculated from first principles the spin and orbital moments of Fe-Co and Co-Ni alloys. The spin-orbit interaction was included at the variational step. The calculations also incorporated orbital polarization, which improved the agreement with the experimental orbital moments. While the spin moments were fairly insensitive to the level of approximation and followed the Slater-Pauling curve, the orbital moments exhibited a more complex behavior, where, for example, the crystal structure plays a most decisive role. Finally, enhanced orbital moments are predicted for Co_1-xNi_x alloys with x∼0.25–0.5 in a hypothetical bcc structure, and for Fe_1-xCo_x alloys with x∼0.25 in a hypothetical fcc structure.