Dielectric Dispersion in K2ZnCl4 around the Incommensurate-Commensurate Phase Transition Point

The complex dielectric constant of K 2 ZnCl 4 was measured in the frequency range from 100 MHz to 800 MHz around the incommensurate-commensurate phase transition point T c . A nearly Debye-type dispersion was observed, of which the relaxation time showed a critical slowing down. The relaxation frequency was about 50 MHz at T c . The static dielectric constant above T c obeys the Curie-Weiss law with the Curie constant of about 95 K. Both the static dielectric constant and the relaxation time showed thermal hysteresis in the incommensurate phase.