Dielectric Relaxation under DC Field in an Antiferroelectric Liquid Crystal MHPOCBC

Linear and nonlinear dielectric measurements under dc electric fields have been performed in an antiferroelectric liquid crystal MHPOCBC to obtain a deeper insight of dynamic properties related to a field-induced phase, designated as , appearing when subjected to electric fields in the phase. We observed a tricritical point in the phase transition. We found two low frequency modes coming from domain walls in the first-order phase transitions to and to SmC. In the third-order nonlinear dielectric measurements another low frequency mode was observed, of which frequency decreases near the transition point. This may be the soft mode responsible for the field-induced transition.