STUDY OF INCOMMENSURATE PHASE-TRANSITION IN [N(CH3)4]2ZNCL4 CRYSTAL BY MEANS OF ULTRASOUND PROPAGATION

Ultrasonic velocity and attenuation measurements for longitudinal modes propagating along the crystallographic axes of {N(CH3)4}2 ZnCl4 crystal were performed over the temperature range covering the prototype, the incommensurate and the commensurate ferroelectric phases. All of measured velocities V[100], V[010] and V[001] show clear anomalies around the prototype-incommensurate phase transition point (T1=20°C), while at the incommensurate-commensurate phase transition point (TC=7°C) only slight anomalies were observed. In attenuation measurements anomalies were also observed at the prototype-incommensurate phase transition point. © 1979, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.