Author/Editor		Kutnjak-Urbanc, B; Žekš, B
Title		Theoretical investigation of the behavior of ferroelectric liquid crystals in a magnetic or in a high-frequency electric field
Type		članek
Source		Phys Rev E
Vol. and No.		Letnik 48, št. 1
Publication year		1993
Volume		str. 455-64
Language		eng
Abstract		A theoretical explanation of the phase diagram of ferroelectric liquid crystals in an external magnetic or high-frequency electric field is given. The investigation is based on a rigorous treatment of the problem within the phenomenological model, being an extension of the Pikin-Indenbom model (Ferroelectrics 20,151 (1978)). The phase transition from the modulated Sm-C phase to the homogeneously ordered Sm-C phase is studied numerically. The relevant parameters of the model are chosen in the best way to fit the experimentally obtained critical-field fines on two ferroelectric liquid-crystalline compounds. As a result, the observed relationship between the critical field and the helical pitch in zero field is theoretically confirmed. The critical-field line is investigated in the vicinity of the Lifshitz point where the metastable states appear. In both compounds, the tricritical point is found to be very close to the Lifshitz point, which seems to disagree with measurements showing hysteresis at all temperatures. This contradiction is removed by showing that, in a sample of a finite length along the helical axis, a slow pitch-relaxation process exists. Consequently, during the critical-field measurements, the system is probably not in an equilibrium, which prevents the continuous phase transition from taking place.
Descriptors		CRYSTALLOGRAPHY ELECTROMAGNETIC FIELDS