Dielectric relaxation studies in ferro-, ferri- and antiferro-electric phases of (S)-4 ′ -octyloxybiphenyl-4-carboxylic acid 3-chloro-4-(1-methylheptyloxycarbonyl)phenyl ester

Author: Pandey M. B.   Dhar R.   Agrawal V. K.   Dabrowski R.  

Publisher: Taylor & Francis Ltd

ISSN: 0141-1594

Source: Phase Transitions: A Multinational Journal, Vol.78, Iss.6, 2005-06, pp. : 457-470

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Abstract

Temperature-dependent dielectric spectroscopy of (S)-4 ′ -octyloxybiphenyl-4-carboxylic acid 3-chloro-4-(1-methylheptyloxycarbonyl)phenyl ester (chlorinated MHPOBC analogue) has been carried out in the frequency range from 1Hz to 10MHz for sample thicknesses 5, 10 and 20µm during heating and cooling runs. This compound shows a rich and complex dielectric response, with several active modes in each subphase. Goldstone-mode relaxation has been observed for , and subphases; however, another relaxation mode (apparently a soft mode) has also been observed in these subphases. It has been found that the dielectric strength corresponding to a relaxation mode increases with increasing thickness of the sample, whereas the relaxation frequency remains invariant. The activation energy of the molecular rotation about their short axes has been determined. It has been found that the molecular reorientation about the short axes is more hindered in chiral smectic C (tilted) subphases than in orthogonal phase.

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