Impulsive stimulated Brillouin scattering studies of the ferroelectric phase transition in tris-sarcosine calcium chloride

Abstract

The longitudinal acoustic-phonon anomalies along all three principal axes of tris-sarcosine calcium chloride near its ferroelectric phase transition were studied using ‘‘impulsive’’ stimulated Brillouin scattering with scattering angles of 23.78° and 6.03°. Logarithmic corrections to mean-field behavior are observed in both phases. Dynamic dispersion analysis of ultrasonic, Brillouin scattering, and the present results confirmed Landau-Khalatnikov order-parameter dynamics with an elementary relaxation time ${\tau }_0$=5.5×${10}^{\mathrm{-}12}$ s K. The unusual acoustic behavior along the polar axis is determined to result from a weak depolarization field and the proximity to a tricritical point. Energy relaxation is believed to be the source of sharp acoustic anomalies along the polar axis which are observed in ultrasonic studies but not in optical experiments which probe higher acoustic frequencies.