Soft Relaxations Near the Ferroelectric Phase Transition in Liquid Crystals

Abstract

Abstract The dispersion of dielectric and optical properties found in experiment yields the relaxation frequencies of the polarization P and the tilt angle θ. The temperature dependences of these frequencies are compared to those obtained from the free energy F(P, θ) describing the ferroelectric phase transition. This comparison shows that order parameters P and θ are strongly coupled in the whole temperature region studied, both showing the same soft-mode relaxation frequency in the SA phase. In the ferroelectric SC . phase the soft-mode relaxation frequency has been detected only when the helicoidal structure has been unwound by a d.c. electric field. On the other hand this d.c. field influences the soft-mode relaxation frequency in the vicinity of the phase transition and the soft-mode dielectric strength even in the whole Sc phase.