Low‐Temperature Anomalies in the CdI2Cd Crystalline System

Abstract

AbstractFrom the measurements of elastic coefficients, piezooptical constants, and dilatometrical lengthening the existence of an improper ferroelastic phase transition of first order in the CdI2Cd single crystalline system within the temperature range 40 to 60 K is found. Different values of the temperature hysteresis are revealed for the piezooptical and elastic constants. From the data obtained an essential role of electron‐phonon interaction in the appearance of the mentioned phase transitions is concluded. The obtained results clearly show that in the CdI2Cd single crystalline system at lower temperatures long‐range forces appear between the impurity subsystems, which due to the specific electron‐phonon interactions tend to the appearance of the phase transitions. The behaviour of the elastic constants and the lengthening indicate the possible ferroelastic nature of these transitions. Simultaneously the existence of the temperature hysteresis reflects the first‐order nature of the mentioned transitions.