Quasicritical behavior of dielectric permittivity in the isotropic phase of n-hexyl-cyanobiphenyl in a large range of temperatures and pressures.

Abstract

Results of studies of the dielectric permittivity and nonlinear dielectric effect (NDE) in the isotropic phase of n-hexyl-cyanobiphenyl are presented. The data reported cover both pressure and temperature dependence. Measurements under atmospheric pressure were carried out in a wide range, up to 100 K from the clearing temperature. The application of a weak measurement frequency (f=67 kHz) resulted in a negligible influence of relaxation processes on NDE results. For both temperature and pressure paths, the dielectric permittivity and the NDE exhibited strong pretransitional effects, described by "critical" exponents phi =1-alpha approximately 0.5 and gamma=1, respectively. Scaling expressions for the pretransitional behavior of the NDE and of the dielectric permittivity have been proposed. The relationship between pretransitional effects in the isotropic phase of nematogens and in critical solutions has also been discussed.