Phase diagram for someHe3-He4mixture films from third-sound experiments

Third-sound velocity measurements in ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-${}_{}{}^4{}_{}{}^{}\mathrm{He}$ mixture films are used to obtain the phase diagram for different coverages. The characterization of these films is discussed, and a correct parameters choice is proposed. Using a rough estimate of the superfluid density, we find that at the superfluid transition temperature the same universal feature as in ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ film is observed. The general behavior of our films is, however, not similar to theoretical predictions for two-dimensional mixtures, and the phase separation is not detected. New experiments are suggested by our results in order to clarify the behavior of mixture films.