%0 Journal Article
%T Effect of magnetism on lattice dynamics in SrFe$_2$As$_2$ as seen via high resolution inelastic x-ray scattering
%A N. Murai
%A T. Fukuda
%A T. Kobayashi
%A M. Nakajima
%A H. Uchiyama
%A D. Ishikawa
%A S. Tsutsui
%A H. Nakamura
%A M. Machida
%A S. Miyasaka
%A S. Tajima
%A A. Q. R. Baron
%J Physics
%D 2015
%I arXiv
%X Phonon spectra of detwinned {SrFe$_2$As$_2$} crystals, as measured by inelastic x-ray scattering, show clear anisotropy accompanying the magneto-structural transition at 200 K. We model the mode splitting using magnetic DFT calculations, including a phenomenological reduction in force-constant anisotropy that can be attributed to magnetic fluctuations. This serves as a starting point for a general model of phonons in this material applicable to both magnetic and non-magnetic phase. Using this model, the measured splitting in the magnetic phase below $\it T_{N}$, and the measured phonon linewidth, we set a lower bound on the mean magnetic fluctuation frequency above $\it T_{N}$ at 210 K.
%U http://arxiv.org/abs/1510.05487v1