M. Glogarova et al., THE THICKNESS MODE CONTRIBUTION TO THE PERMITTIVITY OF FERROELECTRIC LIQUID-CRYSTALS, Molecular crystals and liquid crystals science and technology. Section A, Molecular crystals and liquid crystals, 263, 1995, pp. 245-254
Dielectric properties of a material prepared of valine in the ferroele
ctric SmC phase are studied in the frequency range 100 Hz divided by
1 MHz and for the sample thickness d between 6 and 100 mu m for both h
elicoidal and twisted sample structure. In all studied samples a low f
requency relaxation has been found with the relaxation frequency propo
rtional to 1/d(2) and with the contribution to permittivity proportion
al to d(2). we suggest this relaxation to be assigned to a 'thickness
mode', which is a fluctuation of the molecular twist existing within t
he smectic layers in the direction of the sample plane normal. This tw
ist deformation existing in both helicoidal and twisted samples is fix
ed by the anchoring on the sample surfaces. It is shown that the thick
ness mode is an important source of permittivity in the SmC phase of
the studied material.