Metastability in the commensurate phase of K₂ZnCl₄

A new dielectric anomaly is found at the temperature T-x (260-290 K) in the commensurate (C) phase of K2ZnCl4, which separates the commensurate phase into two states. The C phase above T-x is a metastable state, in which the relaxation of the polarization is expressed by the stretched exponential form, and the C phase below T-x is a stable state in which the dielectric constant and polarization are independent of time. It is speculated that the dielectric anomaly found at the temperature T-x is a stabilization process of discommensurations. This anomaly could be observed only in a measurement performed using a liquid-nitrogen cooler (LNC) without mechanical vibration of the measurement system.