Anisotropic Ultrasonic Properties of a Nematic Liquid Crystal

Ultrasonic measurements (2 to 6 MHz) on a room-temperature nematic liquid crystal have shown the attenuation to vary strongly with the angle $\theta$ between the sound-wave propagation direction and the direction of an aligning magnetic field. The velocity change is quite small, amounting to some 0.1% between the $\theta ={90}^{\circ }$ and the $\theta =0^{\circ }$ case. The orientation-dependent attenuation is of the hysteresis type.