PHASE-DIAGRAM OF HE-3-HE-4 MIXTURE FILMS

Superfluid density and dissipation have been measured as functions of temperature in -43He mixture films using a high-Q torsional oscillator. Transition temperatures between 1.3 and 1.9 K and He3 concentrations between 0.5% and 56% were investigated. In these films the superfluid transition temperature decreases monotonically with He3 concentration. This decrease is linear for smaller concentrations but becomes more rapid at higher concentrations. There were no clear signs of a transition to a phase-separated state observed. All the mixture films exhibit the characteristic universal jump in superfluid density at the transition. The results are compared with the bulk phase diagram and also with a simple phenomenological model. © 1990 The American Physical Society.