Dynamics of Ferroelectric Rochelle Salt

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Abstract
A quantum theory of ferroelectricity in Rochelle salt is developed which is an extension of the two-sublattice model of Mitsui. The isotope effects on deuteration are explained in a natural way, and the spontaneous polarization, the polarization of the two sublattices, and the dielectric constant are obtained as functions of temperature. The dynamics of the system is investigated for the case of deuterated Rochelle salt and is found to exhibit a two-mode relaxational behavior. The correlation time of one of these two modes is proportional to the static dielectric constant and thus exhibits a critical slowing-down on approaching the two Curie temperatures in agreement with the experimental data.