Dielectric Study of Phase Transitions in Cs₃H(SeO₄)₂ and Its Isotope Effect

Abstract

The dielectric constants along the c′ axis of Cs₃H(SeO₄)₂ and its deuterated crystal were measured in a temperature range from 5 K to 460 K. It was found that Cs₃H(SeO₄)₂ undergoes three phase transitions at 451 K, 364 K and 50 K. The dielectric constant of Cs₃H(SeO₄)₂ shows a small peak at 50 K, and it obeys the Curie-Weiss law above 50 K. The transition temperature (50 K) is increased to 168 K by deuteration, showing a large isotope effect, while other two transition temperatures do not change appreciably.