Exchange-Coupled Spin-Fluctuation Theory: Application to Fe, Co, and Ni

Finite-temperature properties are modeled for the itinerant-electron ferromagnets Fe, Co, and Ni by employing a spin-fluctuation theory where the modes are coupled by interatomic exchange interactions. Our method is based on the density functional theory using the local density approximation. The latter yields all parameters derived from constrained ground-state properties of noncollinear spin configurations to calculate ab initio the Curie temperatures, the magnetic susceptibilities, and, furthermore, the hcp-fcc phase transition of Co. Our results are in fair agreement with experimental data.