Ultrasonic Study near the Ferroelectric Phase Transition of RbHSO₄

Abstract

The anomalous ultrasonic attenuation and velocity of the longitudinal wave propagating along the b-axis perpendicular to the ferroelectric axis (c-axis) of RbHSO₄ have been measured as functions of temperature and frequency near the transition temperature T_C. By assuming the single relaxation process of the fluctuation induced by the ultrasonic wave at each temperature, the relaxation time τ has been analyzed. Above T_C thus obtained relaxation time indicates a cross-over behavior in which the relaxation time has the exponent of n≈0.3 for T−T_C<0.2°C and the exponent of n≈2 for T−T_C>0.2°C. The former and the latter relaxation processes seem to be related to the energy and the polarization relaxation processes, respectively. The similar cross-over behavior has been obtained below T_C.