Experimental studies on ferroelectricity in Rb2ZnCl4

Phase transition in ferroelectric Rb2ZnCl4 are examined by the ac calorimeter and the DTA technique. Small heat anomalies are seen around both of the two transition points. The dielectric constant in the direction α, ϵα, is measured as a function of temperature on heating and cooling. The Curie-Weiss law is found to hold above the lower transition point. The 60 Hz D-E hysteresis loop is observed in detail for a wide range of applied fields at each temperature. Triple form of the loop and anomalous temperature- and field-dependence of the spontaneous polarization infer that the ferroelectricity in Rb2ZnCl4 is ferrielectricity in reality.