Frequency variation of periodic distortion thresholds in a nematic liquid crystal

Abstract

Investigations are reported on the electric field induced orientational transitions in the bend Freedericksz geometry under the action of a stabilizing magnetic field. When the magnetic field is strong enough, the deformation above electric threshold is periodic with the periodicity disappearing at a higher voltage. The alignment does not remain homeotropic below threshold and the sample exhibits pretransitional biaxiality. Every transition is discontinuous and accompanied by hysteresis. The expected form of scaling appears to hold for all the observed thresholds. The thresholds and the direction of the wave vector are frequency dependent, showing that the instability mechanism involves electrical conductivity.