Ultrasonic investigation of the normal-incommensurate-commensurate phase transitions in Rb 2 ZnCl 4 and K 2 ZnCl 4

Abstract
An ultrasonic attenuation has been measured near the normal-incommensurate phase transition point of Rb2ZnCl4. Elastic relaxation times have been estimated both above and below the transition point. An anomaly of the shear stiffness c55 of K2ZnCl4 around the incommensurate-commensurate transition point is also reported.