Spin wave dispersion of 3d ferromagnets based on QSGW calculations

We have calculated spin wave (SW) dispersion by combining the quasi-particle self-consistent $GW$ (QSGW) and linear response method for transverse dynamical susceptibility $\chi^{+-}({\bf q},\omega)$. We compared the QSGW and the local density approximation (LDA) for bcc Fe, hcp Co, fcc Ni, and B2-type FeCo. The QSGW shows that spin stiffness constants $D$ of Fe, Co, and Ni are all in good agreement with experimental values. Particularly in Ni, the QSGW reproduces the prediction of $D$ compared to the previous LDA calculations. In the case of Co, the QSGW reproduces both acoustic and optical branches in SW dispersion around A-point in the 1st Brillouin zone. As for FeCo, we found the optical branch is strongly damped by Stoner excitation in contrast to less damping for the acoustic branch.