The existence of four dielectric modes in the planar oriented S*c phase of a fluorinated substance

Abstract

Soft mode and Goldstone mode properties have been studied for a fluorinated substance. The dielectric spectra have been measured on the planar oriented samples, in the frequency range from 10 Hz to 10 MHz. The thickness of the sample was 10 μm and two kinds of capacitors were used: (i) a low resistance EHC cell and (ii) gold coated electrodes. A bias field up to 10kV cm^?1 has been applied to show the existence of both the soft mode and domain mode in the S*_c phase below T _c. In the S*_c phase a strong Goldstone mode has been observed with a low critical frequency (v ^G _C = 15 Hz). The high frequency side at the Goldstone mode spectrum is accompanied by a shoulder which consists of the soft mode and domain mode as well. In the vicinity of the S*_A-S*_C transition the dielectric parameters of the soft mode obey a Curie-Weiss law. The slope ratio is equal to ?1·62 for the inverse of dielectric increments (Δ∈^?1) and ?1·73 for the critical frequencies (v _c) obtained by using gold electrodes. The respective values received for the EHC cell are ?4·14 and ?2·1. The dielectric parameters of the domain mode have been obtained versus temperature and bias field. We can qualitatively show that a high frequency molecular relaxation is present in the S*_A and S*_C phases as the high frequency limit of dielectric permittivity is distinctly higher than the refractive index squared.