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

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. Measurem ents under atmospheric pressure were carried out in a wide range, up to 100 K from the clearing temperature. The application of a weak measurement fre quency (f = 67 Mit) resulted in a negligible influence of relaxation proces ses on NDE results. For both temperature and pressure paths, the dielectric permittivity and the NDE exhibited strong pretransitional effects, describ ed by "critical" exponents phi=1 - alpha approximate to 0.5 and gamma=1, re spectively. Scaling expressions for the pretransitional behavior of the NDE and of the dielectric permittivity have been proposed. The relationship be tween pretransidonal effects in the isotropic phase of nematogens and in cr itical solutions has also been discussed. [S1063-651X(99)05205-8].