Anisotropic Ultrasonic Properties of a Smectic Liquid Crystal

Abstract

Ultrasonic measurements have been made in an oriented smectic liquid crystal. The material was aligned by cooling through the liquid crystal-isotropic liquid transformation in the presence of a 12.4-kOe magnetic field. The ultrasonic attenuation is significantly more anisotropic than it is in nematics. The velocity also has a measurable anisotropy (\ensuremath{\sim} 5%). The velocities give certain of the elastic constants in de Gennes's theory of the smectic state.