Tilt susceptibility and bare correlation length at a smectic-A-smectic-C phase transition

We report measurements and data analysis of the tilt susceptibility at the Sm-A-Sm-C transition of azoxy-4,4'-di-undecyl-α-methylcinnamate. We deduce the critical exponent of the transition γ = 1.28 ± 0.03 and the bare correlation length ξ 0 ∼ 2-5 Å. These results are consistent through the Ginzburg criterion, with a non-classical behaviour at the transition.