Soft-Phonon Response Function: Inelastic Neutron Scattering from LaA1
- 1 August 1973
- journal article
- research article
- Published by American Physical Society (APS) in Physical Review B
- Vol. 8 (3), 1119-1124
- https://doi.org/10.1103/physrevb.8.1119
Abstract
High-resolution inelastic-neutron-scattering measurements have been performed at the cubic-rhombohedral () phase transitions in a low-mosaic flux-grown single crystal of LaA1. The transition occurred at (489 ± 2) °C, somewhat lower than reported for Verneuil-grown samples. The scattering from the soft mode at the corner of the Brillouin zone in the cubic phase exhibits the central component up to 610 °C. In addition, phonon sidebands centered around are observed which are overdamped below 550 °C. The observed intensities are well described by a model which relates the central component to the phonon sidebands through an anharmonic coupling parameter , as recently reported by Shapiro et al. for SrTi. is found to deviate from the mean-field behavior near the transition temperature and is found to be nearly constant. A comparison is made between LaA1, SrTi, and KMn with respect to these parameters as well as the anisotropy of the dispersion surfaces near the point.
Keywords
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