Frequency Dependent Threshold in Bend Geometry of 5CB

Abstract

We report the effect of electric frequency on deformation threshold in the bend Freedericksz geometry in the presence of a stabilizing magnetic field applied normal to the plates with the destabilizing electric field impressed parallel to the sample. In general, the observed threshold and deformation above it are strongly dependent on frequency and magnetic strength associated with a pretransitional field-induced biaxiality. The periodic deformation observed under a strong magnetic field has wavevector along the electric field at low frequencies. Above a cut-off frequency, the direction of the wavevector becomes normal to the electric field. Hysterisis is present between increase and decrease of voltage. At dc or low frequency excitation, there is clear evidence of hydrodynamic flow which can become turbulent for some values of parameters.