Static and Dynamic Critical Properties of Dielectric Constant in Ferroelectric CsH₂PO₄ and CsD₂PO₄

Abstract

Monodispersive dielectric dispersion has been observed in CsH₂PO₄ and CsD₂PO₄ in the frequency range between 1 MHz and 1 GHz. Critical anomalies found in the static dielectric constant and the relaxation time, ε_s^H and τ^H for CsH₂PO₄ and ε_s^D and τ^D for CsD₂PO₄, respectively, show pronounced deviations from the Curie-Weiss behavior. Simple relations of ε_s^D⁄ε_s^H=1.3 and τ^D⁄τ^H=5.2 for the values at the same T−T_c, where T_c is the transition temperature of each material, are found in wide temperature ranges above T_c. It is hard to explain these results by the tunneling model.