Nonlinear dielectric investigation of ferroelectric liquid crystals

The dynamical characteristics of ferroelectric liquid crystals were investigated by means of nonlinear dielectric measurements such as D-E hysteresis, ∈-E hysteresis loop, nonlinear relaxation spectra, and bias-field-dependent linear relaxation spectra. Molecular motions considered were the thermally activated Goldstone mode and the field-induced switching mode. The Goldstone mode is highly suppressed by the switching mode due to loss of helical structure. Although they arise from a common elementary process related to the azimuth angle, they are distinguished by the difference in nonlinear nature that the saturated polarization of the former remains one half that of the latter. This implies that there exists a potential barrier in the midway of large-amplitude Goldstone mode fluctuations