Nuclear Alignment and the Entropy of LiquidHe3

Abstract

By consideration of the melting pressure data it is shown that calculations implying that the nuclear spins in liquid ${\mathrm{He}}^3$ are appreciably aligned at temperatures above 0.5°K are inconsistent with the assumption that the nuclear spins are randomly oriented in the solid. The expression $S_{\mathrm{liq}}=R\ln 2+0.344RT+0.013R{T}^3$ for the entropy of liquid ${\mathrm{He}}^3$ (including the nuclear spin entropy) is consistent with the vapor pressure data from 1.0°K to 2.5°K and with the melting pressure data from 0.5°K to 1.5°K.