Dielectric permittivity of ferroelectric liquid crystals influenced by a biasing electric field

Abstract

A bias field dependence of dielectric permittivity ∊'(E) of ferroelectric liquid crystals DOBAMBC and a mixture of DOBAMBC with Sm C substance in a planar Sm C* sample shows four different frequency regions. In two of them the unusual behaviour—increase of ∊' with increasing E—is observed. The first increase found in the frequency range about 1 kHz ÷ 4 kHz is a consequence of the field induced increase of the relaxation frequency of the low frequency relaxation mechanism. The second increase detected above 40 kHz is explained by the change of sign of the dielectric anisotropy which takes place above the other relaxation frequency connected with rotation of molecules along their short axes. The other two regions exhibiting decrease of ∊' with increasing field are also discussed.