Investigation of the effect of uniaxial stress on the elastic properties of Rb₄LiH₃(SO₄)₄

Abstract

In this project, ultrasonic measurements have been used in order to observe the influence of uniaxial stress on the elastic properties of the ferroelastic compound Rb₄LiH₃(SO₄)₄. The experimental results are compared to predictions derived from a Landau model. In the experiment, uniaxial stresses either along [100] or [010] direction have been applied using two piezo-actuators mounted on opposite faces of the crystal. The temperature and pressure ranges for this investigation arc 100 - 150K and 0 - 0.27 kbar, respectively. Throughout the investigation, it has been observed that in the absence of stress, the sound velocity along the x and z -axes shows a distinct step-like variation in the vicinity of the transition temperature, Tc = 134 K. The amplitude of the step-like variation is found to decrease with the application of a uniaxial stress. We believe that this is principally due to a reconfiguration of the domain distribution into the ferroelastic phase. This is supported by our Landau model which predicts no large variation over this pressure range.