Peculiarities of Dielectric Spectroscopy of Ferroelectric Nematics

Dielectric spectroscopy is known as one of the most powerful technique for studying ferroelectric and other polar materials. Since the discovery of ferroelectricity in LCs it was successfully employed for characterization of ferro-, antiferro- and ferri-electric liquidcrystalline phases. However, recently the Boulder group raised the question of the applicability of dielectric spectroscopy for characterization ferroelectric nematics due to parasitic effect of the insulating alignment layers. This effects on the apparent/measured values of the dielectric permittivity. In this paper we study this effect in greater detail. The following issues will receive special attention. Are the real values of dielectric permittivity lower or higher than the measured ones? Can the real values of dielectric permittivity be recovered in the cell with alignment layers? We also provide an example of the effect of insulating alignment layers in non-ferroelectric nematic phase.