<i>Ab initio</i>calculations of exchange interactions, spin-wave stiffness constants, and Curie temperatures of Fe, Co, and Ni

TLDR

We computed Heisenberg exchange parameters for bcc Fe, fcc Co, and fcc Ni using a nonrelativistic spin‑polarized Green‑function technique within the tight‑binding linear muffin‑tin orbital method, applied the magnetic force theorem to evaluate energy changes from local magnetization rotations, and derived spin‑wave stiffness constants and Curie temperatures via Fourier transforms and mean‑field/random‑phase approximations, while addressing convergence and regularization. The Curie temperatures obtained from the Green‑function random‑phase approximation are in better agreement with experimental data than those from the mean‑field approximation.

Abstract

We have calculated Heisenberg exchange parameters for bcc Fe, fcc Co, and fcc Ni using the nonrelativistic spin-polarized Green-function technique within the tight-binding linear muffin-tin orbital method and by employing the magnetic force theorem to calculate total energy changes associated with a local rotation of magnetization directions. We have also determined spin-wave stiffness constants and found the dispersion curves for metals in question employing the Fourier transform of calculated Heisenberg exchange parameters. Detailed analysis of convergence properties of the underlying lattice sums was carried out and a regularization procedure for calculation of the spin-wave stiffness constant was suggested. Curie temperatures were calculated both in the mean-field approximation and within the Green-function random-phase approximation. The latter results were found to be in a better agreement with available experimental data.