Magnons play an important role in fast precessional magnetization reversal processes serving as a heat bath for dissipation of the Zeeman energy and thus being responsible for the relaxation of magnetization. Employing \emph{ab initio} many-body perturbation theory we studied the magnon spectra of the tetragonal FeCo compounds considering three different experimental c/a ratios, c/a=1.13, 1.18, and 1.24 corresponding to FeCo grown on Pd, Ir, and Rh, respectively. We find that for all three cases the short-wave-length magnons are strongly damped and tetragonal distortion gives rise to a significant magnon softening. The magnon stiffness constant D decreases almost by a factor of two from FeCo/Pd to FeCo/Rh. The combination of soft magnons together with the giant magnetic anisotropy energy suggests FeCo/Rh to be a promising material for perpendicular magnetic recording applications.
@article{arxiv.1304.7091,
title = {Strong magnon softening in tetragonal FeCo compounds},
author = {Ersoy Sasioglu and Christoph Friedrich and Stefan Blügel},
journal= {arXiv preprint arXiv:1304.7091},
year = {2015}
}