Noncollinear magnetism of Fe-rich Fe-Ni alloys

Abstract

The magnetic structure of Fe-rich FeNi alloys has long been a subject of great scientific interest and controversy. In this study, the authors attempt to understand an interesting phenomenon that the average magnetic moment of the alloys in the γ-phase (fcc) decreases dramatically in the composition range near 70% Fe. Although the observation was made more than 30 years ago, the nature of the mechanism for this moment collapse is still controversial. In this approach, the noncollinear locally self-consistent multiple-scattering (LSMS) method is applied to the magnetic structure calculation of large unit cell samples consisting of Fe and Ni atoms. The Fe and Ni atoms are randomly distributed on a fcc lattice. The moment directions are initialized to be randomly oriented and then, as the self-consistent iterations proceed, are allowed to rotate to minimize the total energy. Astable magnetic structure of the alloy is determined by the final moment configuration. Results are compared with experiments and the possible existence of noncollinear magnetic structures are discussed.