Evidence of Nuclear Spin Ordering in Solid Helium-Three

Abstract

Measurements of the pressure versus temperature for constant-volume samples of solid ${\mathrm{He}}^3$ to 20 mdeg K show the expected $T^{-1\mathrm{}}$ dependence due to spin ordering at low temperatures. A value for the exchange integral $\frac{\mathrm{}\left|J\right|\mathrm{}}{k}$ of about 0.7 mdeg K is obtained for a molar volume of 24 ${\mathrm{cm}}^3$, with $\frac{\partial \ln \mathrm{}\left|J\right|\mathrm{}}{\partial \ln V}=16.4\mathrm{}$.