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 ${T}^{\ensuremath{-}1}$ dependence due to spin ordering at low temperatures. A value for the exchange integral $\frac{|J|}{k}$ of about 0.7 mdeg K is obtained for a molar volume of 24 ${\mathrm{cm}}^{3}$, with $\frac{\ensuremath{\partial}\mathrm{ln}|J|}{\ensuremath{\partial}\mathrm{ln}V}=16.4$.