Spin-Density-Wave Fluctuations in Copper Nuclear Spins

Abstract
A spherical-model calculation of the spin-density-wave fluctuations in copper nuclear spins is presented. The results are compared with an experiment where copper nuclear spins have been cooled to below 0.1 μK. The agreement, with no adjustable parameters, is found to be satisfactory for spin susceptibility, entropy, and internal energy. A considerable depression of the transition temperature from its mean-field value, in qualitative agreement with the experiments, is also found.