Abstract
Phonon spectra of detwinned crystals, as measured by inelastic x-ray scattering, show clear anisotropy accompanying the magnetostructural 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 the antiferromagnetically ordered phase and the paramagnetic phase. Using this model, the measured splitting in the magnetic phase below , and the measured phonon linewidth, we set a lower bound on the mean magnetic fluctuation frequency above at 210 K.
- Received 9 October 2015
- Revised 1 December 2015
DOI:https://doi.org/10.1103/PhysRevB.93.020301
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