Temperature Scale for Neodymium Ethylsulfate Below 1 °K

A thermodynamic method, $\gamma$-ray heating a statistical-mechanical method, and nuclear orientation, were used in a complementary fashion to determine the final temperature reached on demagnetizing a single crystal of neodymium ethylsulfate (NES) from magnetic fields up to 20 kG, applied along the $c$ axis at 1 °K. The temperature scale so established allows nuclear-orientation data to be fitted much more satisfactorily than did the old scale, removing a troublesome S-shaped deviation. Two independent checks were made of the validity of the new scale. The nuclear magnetic moment of ${\mathrm{Ce}}^{137m}$ is again corrected. The best value, obtained from orientation in both NES and cerium magnesium nitrate lattices is 0.69±0.03 nm, using ${〈r^{-3\mathrm{}}〉}_{4f}=4.44\mathrm{}$ atomic units.