Nonlinear dielectric constants $∈^'_n$ (real part) and $∈^'_n$ (imaginary part) of higher order harmonic responses(upto n=9) were measured in $KH_2PO_4$(KDP) crystal near the domain wall freezing temperature $T_f \simeq 96K$ by use of a precision dual phase lock-in amplifier system. The observed dependence of $∈^'Ⅰ_n$ and $∈^'_n$ on the a.c. field amplitude can be understood in terms of the nonlinear polarization dynamics as due to the domain wall motions characterized by a critical field $E_c$, a power law exponent α, and phase retardation φ.
We measured the frequency dependence of D-E hysteresis loop in $CsH_2PO_4$ crystal, and also calculated the D-E hysteresis loop of the 2D Ising model with strongly anisotropic ferroelectric coupling. Hysteresis loops are analyzed by the extended Avrami model which is recently proposed by Orihara et al. Experimental and simulation data are found to be good agreement with the extended Avrami model employing two different growth-dimensions for the initial and the final regime of the polarization reversal process.
We have investigated the electro-optic transmittance of surface stabilized ferroelectric liquid crystal under various a.c. field amplitudes, frequencies, and temperatures. Dynamic behaviour of ferroelectric liquid crystal was derived from both electro-optic transmittance and D-E hysteresis loop measurements, the latter contained an additional distortion due to electric conductance of liquid crystal. Hysteresis loop of the electro-optic transmittance of SSFLC are found to well follow the scaling law, A~E_o^{0.44}f^{0.13}$ in the f→0 limit, in good agreement with the general area scaling function proposed by Ackaryya et al. for all frequencies. We calculated the switching time, when large competition between the characteristic time of FLC and the a.c. field periods enters, using the general area scaling function.
