Heat-Capacity Study of the Transition from a Stacked-Hexatic-BPhase to a Smectic-APhase

Abstract

High-resolution ac calorimetry measurements have been performed on a liquid-crystal material exhibiting a stacked-hexatic-$B$—smectic-$A$ phase transition. The transition appears to be second order with a pronounced, symmetric heat capacity peak and no observable thermal hysteresis. The data can be fitted by a power law divergence with critical exponents $\alpha ={\alpha }^{\prime }=0.64\mathrm{}\pm 0.04$ and a ratio of critical amplitudes $\frac{A}{A^{\prime }}=0.83\mathrm{}$. Measurements have also been carried out on a crystalline-$B$-smectic-$A$ transition which is found to be first order.