Anomalies of hypersound velocity and attenuation in ferroelectric tris-sarcosine calcium chloride (TSCC) for small-angle and right-angle Brillouin scattering and Brillouin backscattering

Abstract

The Brillouin spectra of ferroelectric tris-sarcosine calcium chloride have been observed using small-angle and right-angle scattering and also backscattering. For different-frequency phonons along the same direction, analogous anomalies in the sound velocity and the attenuation are seen. The smallest angle we have achieved is 7.48\ifmmode^\circ\else\textdegree\fi{}. The temperature and frequency dependences of the sound velocity are discussed. The fact that the linewidth maximum for [001] phonons occurs somewhat below ${T}_{c}$ seems to indicate that the anomalies are due to piezoelectric coupling induced by spontaneous polarization below ${T}_{c}$. For [010] phonons the elementary relaxation times which relate to the energy are estimated as ${\ensuremath{\tau}}_{0}^{E}$=5.25\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}13}$ sec above ${T}_{c}$ and ${\ensuremath{\tau}}_{0}^{E}$=3.32\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}12}$ sec below ${T}_{c}$. The phonon attenuations are also estimated and compared with the observed ones. For the [001] phonons the elementary relaxation time is estimated as ${\ensuremath{\tau}}_{0}$=5.25\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}14}$ sec, in good agreement with the value obtained from right-angle Brillouin scattering.