Low Temperature Melting Curve of He-3

Measurements of the melting curve of He-3 have been made from 3 m degrees K to 40 m degrees K, after cooling the liquid-solid He-3 mixture by the adiabatic solidification method. The slope of the melting curve shows that at the lowest temperature there is a substantial departure of the solid He-3 entropy from R ln 2. This effect is due to nuclear spin ordering. Temperatures below 3 m degrees K were obtained during compression. By theoretically estimating the melting curve below 3 m K it is possible to estimate temperatures from pressure measurements. By such means it is estimated that Kelvin temperatures of 1.5 to 2 m degrees K were actually achieved.