Origin of the anomalous electroclinic susceptibility exponent in a ferroelectric liquid crystal

Crossed magnetic and electric fields were applied to the chiral liquid crystal p-decyloxybenzylidene-p’-amino-2-methyl- butylcinnamate (DOBAMBC) in the smectic-A phase in such a way as to maintain the director orientation normal to the smectic layers. Near the smectic-$C^{\mathrm{*}}$ transition it was found that E∝$H^2$ and that dE/${\mathrm{dH}}^2$ versus temperature exhibits behavior consistent with a temperature-dependent polarization-tilt coupling coefficient. This result offers an explanation for the anomalous electroclinic susceptibility exponent γ=1.11 observed by Garoff and Meyer [Phys. Rev. Lett. 38, 848 (1977)].