Dynamics of polarization reversal in purified Rb2ZnCl4

The dynamics of polarization reversal in sinusoidal fields (0. 1Hz≤f≤50kHz) was studied in the ferroelectric lock-in phase of purified Rb2ZnCl4 crystals. The frequency dependence of remanent polarization and coercive field Ec is qualitatively the same above and below T*≈160K, where for all measuring frequencies Ec starts to increase rapidly with decreasing temperature. A model which treats sideways shifts of planar, nearly regularly arranged domain walls as the only mechanism of polarization reversal in Rb2ZnCl4 is applicable for the quantitative description of ferroelectric hysteresis loops in the whole temperature interval under investigation. The anomalous increase of Ec at T* seems to be connected to a corresponding increase of the viscosity coefficient.