Nuclear spin ordering in solidHe3

Abstract

The recent experiments of Kummer et al., as well as Collan and Halperin et al., on the melting curve of $^{3}\mathrm{He}$ are analyzed with a localized Heisenberg Hamiltonian. They can be described consistently only with ferromagnetic nearest-neighbor and antiferromagnetic next-nearest-neighbor exchange constants that imply a positive Weiss constant, $\ensuremath{\Theta}=1.04$ mK. These exchange constants can only with difficulty be made consistent with those derived previously with the same Hamiltonian from experiments at smaller molar volumes.