GLOBAL THERMAL HYSTERESIS OF POLARIZATION REVERSAL IN PURIFIED RB2ZNCL4 CRYSTALS

Ferroelectric P(E)-hysteresis loops were recorded in the lock-in phase of purified Rb2ZnCl4 crystals at two different frequencies f = 100 Hz and f = 1 kHz. The comparison of results obtained on cooling and heat ing, respectively, reveales a pronounced thermal hysteresis of the coe rcive field E-C above the temperature T approximate to 160 K where E- C(T) changes its slope. Below T, E-c(T) is an unambigious function of temperature. The analysis of experimental data in terms of a model, w hich treats sideways shifts of a field independent number of planar, n early regularly arranged domain walls to be the only mechanism of pola rization reversal in Rb2ZnCl4 indicates that the thermal hysteresis at T > T can be attributed to a corresponding hysteresis of the domain wall density n.