Excess heat capacities of 3He films adsorbed on Grafoil

Excess heat capacities ( C ex ) both in the first- and second-layer 3 He films adsorbed on Grafoil substrate have been measured at temperatures down to 100 μK . With increasing density, the high-temperature C ex increases rather abruptly somewhat before the second-layer promotion in the uniform film. Otherwise, C ex is roughly density-independent. The results are consistent with the model that C ex arises from nuclear-spin degrees of freedom in the amorphous 3 He adsorbed on substrate heterogeneities and that the amorphous 3 He has also a layered structure.