Pinning Effect on Dynamical Dielectric Properties of Rb2ZnCl4 in the Incommensurate Phase

Dielectric dispersion has been studied for several crystals of Rb 2 ZnCl 4 prepared under different conditions in the frequency range from 10 3 Hz to 10 9 Hz around the incommensurate-commensurate phase transition temperature T c . Although the dielectric dispersion of the relaxational type is observed for all the crystals, the apparent critical slowing down is found only for the less defective crystals in which the relaxation is monodispersive in the temperature range T > T c +5 K, but becomes polydispersive near T c in the incommensurate phase. In the defective crystals, a wide distribution of the relaxation times was observed in the whole temperature range of the incommensurate phase.