LOW AND HIGH-FREQUENCY DIELECTRIC-SPECTROSCOPY ON A LIQUID-CRYSTAL WITH THE PHASE SEQUENCE N-ASTERISK-SA-SC-ASTERISK

Broadband dielectric measurements on a multicomponent ferroelectric li quid crystal mixture have been performed. The alignment was homeotropi c and the cell and sample holder were the same in the whole frequency range. Two relaxation processes have been observed in all liquid cryst al phases with shapes given by the Havriliak-Negami and inverted Havri liak-Negami functions. Strengths and frequencies of both modes have be en obtained for the different phases. The values of the latter and the ir activation energies allowed us to assign the low and high frequency mechanism to the molecular reorientation around the transversal axis and around the longitudinal axis, respectively. The behaviour of this high frequency mode does not show any jump in the S(A)-S(C) phase tra nsition, neither in the amplitude nor in the frequency, indicating tha t the appearance of the spontaneous polarization in the S(C) phase is not the consequence of the freezing of this mode.