Nuclear Magnetic Resonance in Cerous Magnesium Nitrate at Temperatures below 1°K

The nuclear resonance of the protons in cerous magnesium nitrate, ${\mathrm{Ce}}_2$ ${\mathrm{Mg}}_3$ ${\left(\mathrm{N}{\mathrm{O}}_3\right)}_{12}$·24${\mathrm{H}}_2$O, has been studied in a single crystal cooled to temperatures below 1°K by partial adiabatic demagnetization and adiabatic rotation. The area under the nuclear resonance was used as a thermometric parameter. The area did not obey Curie's law as a result of the temperature-dependent local rf field. A $T-T^{*}$ relation was derived which gave temperature ratios on adiabatic rotation which agreed within 5-10% with ratios calculated from the properties of the crystal. The lowest measured temperature was 5×${10}^{-3\mathrm{}}$°K.