MELTING OF HE-3 IN A PHASE-SEPARATED SOLID HE-3-HE-4 MIXTURE

The melting pressure of the He-3-rich phase, which is formed after pha se separation of a mixture of 0.6% He-3 in He-4, has been studied in t he temperature range 1-150 mK, below the phase-separation temperature T-ps, at pressures between 2.78 and 3.56 MPa. Measurements were made w ith the mixture confined in a silver sinter, and also in an open volum e for comparison. An elevation of the melting pressure relative to pur e He-3 of up to 60 kPa in the sinter cell and 20 kPa in the open-volum e cell was observed. Hysteresis between the freezing and melting tempe ratures was found for both cells, similar to that observed for pure He -3 in small pores. The results of Schrenk et al. for heat capacity mea surements on a similar system are discussed. (C) 1997 American Institu te of Physics.