Nuclear Specific Heats in Paramagnetic Salts

Abstract

This paper considers theoretically the contribution to the specific heat arising from the hyperfine structure, i.e., from the interaction of the magnetic moment and electric quadrupole moment of the nucleus with its surroundings. This contribution is important only at low temperatures, where it is approximately of the form $\frac{A}{{T}^{2}}$. The coefficient $A$ is calculated for a number of copper, manganese, and cobalt salts. Agreement with the limited amount of experimental data available is reasonably good. The influence of the hyperfine structure on the magnetic susceptibility is negligible unless the temperature is exceedingly low, for even in single crystals it begins only with terms of the third order in a series development in $\frac{1}{T}$. In manganese ammonium sulphate, the electronic Stark splitting deduced from paramagnetic resonance at 20\ifmmode^\circ\else\textdegree\fi{} and 90\ifmmode^\circ\else\textdegree\fi{}K does not agree with that obtained from the paramagnetic anisotropy between 90\ifmmode^\circ\else\textdegree\fi{} and 300\ifmmode^\circ\else\textdegree\fi{}K.