AC CALORIMETRIC STUDIES OF PHASE-TRANSITIONS IN POROUS SUBSTRATES - SUPERFLUID-HELIUM AND LIQUID-CRYSTALS

In this review, we detail the application of an AC calorimetry techniq ue as it has been employed and optimized for the study of phase transi tions, particularly the superfluid-to-normal transition and those unde rgone by liquid crystals systems while confined to geometries more res trictive than bulk. The theory of operation, the sample preparation, a nd the electronic equipment involved in such measurements are describe d in detail. Examples of its use in heat capacity measurements of two- dimensional helium films at sub-Kelvin temperatures and in liquid crys tal studies, a discussion on the simultaneously measured phase shift, which contains information regarding the order of the phase transition , is also included. (C) 1997 Elsevier Science B.V.