THE INFLUENCE OF UNIAXIAL-STRESS ON ULTRASONIC WAVE-PROPAGATION IN FERROELASTIC (NH4)(4)LIH3(SO4)(4)

The influence of uniaxial stress sigma(2) on the temperature dependenc e of velocity and attenuation of the longitudinal ultrasonic wave prop agating along the [001] direction of a ferroelastic ALHS was investiga ted. A distinct step-like change in velocity was observed at T-C for s igma(2)=0. This anomaly was found to decrease with increasing stress. Simultaneously, an anomalous increase of attenuation coefficient was o bserved when the stress applied was higher than coercive stress. This fact was attributed to the local inhomogeneous deformations which are the remains of ferroelastic domain walls. (C) 1997 Elsevier Science Lt d.