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

The nuclear resonance of the protons in cerous magnesium nitrate, Ce₂{Mg}₃(NO₃)₁₂·{}24H₂O, 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^∘{}K.A study of the structure of the resonance showed that the splittings were caused by the average magnetization of the cerium ions and that the protons were at least 5 A from the cerium ions.