Nuclear adiabatic demagnetization of two proton systems in singlet ground state magnetic salt

The production of magnetic ordering in a nuclear spin system subjected only to dipole-dipole interaction requires exceedingly low temperature, which is about 1 μK or less. To produce such low temperature, the only method to be used is adiabatic demagnetization of the nuclear spin system, and because of long spin-lattice relaxation time at low temperature, it is easier to cool only the nuclear spins, whereas the lattice remains at relatively high temperature. In this case, the heat insulation between the heat bath and the sample is unnecessary, and the experimental apparatus becomes very simple. The experimental method and the result for the production of magnetic ordering in the proton spin system of an insulating salt in the laboratory frame are reported. The sample, Cu(NO3)2.2.5 H2O among singlet ground state magnetic salts was adopted. The crystal symmetry of this sample crystal is monoclinic, and the space group belongs to I2/a. The energy levels of the Cu++ pairs in an external field, the temperature dependence of the spin-lattice relaxation time of protons in Cu(NO3)2.2.5 H2O, the temperature and field dependence of spin-lattice relaxation time, the relation between the spin temperature after demagnetization and the temperature of the thermal bath in two series of experiments in the final fields of 1174 Oe and 8/Oe, and the energy levels of protons of water molecule of hydration which couple to each other by intramolecular dipole-dipole interaction in an external field are explained. (Nakai, Y