An acoustic anomaly at the phase transition in GeTeSnTe alloy single crystals

Abstract The ultrasonic wave velocities and attenuation have been measured in single crystals of 20 mole.% GeTeSnTe alloys between 90 and 373°K. The ultrasound velocities and thus the elastic constants show a step-like behaviour, which is accompanied by a peak in the attenuation, at the cubic to rhombohedral transformation temperature (240°K). In the vicinity of the transition a strong interaction occurs between the acoustic phonon modes and the soft TO mode.