Phonon spectra of detwinned {SrFe2As2} 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 TN, and the measured phonon linewidth, we set a lower bound on the mean magnetic fluctuation frequency above TN at 210 K.
@article{arxiv.1510.05487,
title = {Effect of magnetism on lattice dynamics in SrFe$_2$As$_2$ as seen via high resolution inelastic x-ray scattering},
author = {N. Murai and T. Fukuda and T. Kobayashi and M. Nakajima and H. Uchiyama and D. Ishikawa and S. Tsutsui and H. Nakamura and M. Machida and S. Miyasaka and S. Tajima and A. Q. R. Baron},
journal= {arXiv preprint arXiv:1510.05487},
year = {2016}
}
Comments
Accepted for publication in Phys.Rev.B (Rapid Communications)