Observation of Major Depression in the Melting Curve of Polarized HELIUM-3.

Since Castaing and Nozieres suggested a method for the production of polarized liquid He-3, there have been several experiments attempted, the latest being by a group in Grenoble, France. The experiments to date are neither exhaustive nor conclusive. The depression in the melting curve predicted has been seen but not systematically studied. The reported studies of the melting curve were performed in a plastic pancake compressional cell with a dynamic range sufficient to fully melt a solid sample of He-3 at 34.34 bars. During slow meltings, ranging from 1 min to 1 hour, an anomalous coexistence of solid and liquid was observed at pressures substantially below the equilibrium melting curve. The existence of the anomaly for such long periods contradicts earlier experiments which suggest decay times around 6 secs. The European experiments were simulated in this work by halting the melting in the partially melted sample, when decay times suggestive of their time constants were obtained. This decay of the pressure anomaly is observed to strongly depend on the magnetic field and the temperature. The relaxation time is longer for higher fields and lower sample temperatures. The melting models considered are Castaing's equal equivalent field melting, the equal polarization melting proposed in this work, and Castaing's latest model which is a compromise of the above two models. Analysis of the 8 Tesla melting data, in which the average cell polarization is near 65%, shows that it favours the equal polarization melting model.