Magnetism of a Nucleus-Electron Complex System in the Vicinity of the Threshold

Magnetic properties of the nucleus-electron complex system which has the electronic singlet ground state are reanalyzed numerically in the vicinity of the threshold D /2 J =1, D being the energy splitting between the electronic ground and excited states. The spontaneous polarization of the electron spin increases steeply far below T c by the effect of the nuclear spin. A fair agreement with the neutron diffraction experiment can be obtained for the praseodymium metal if it is assumed that the praseodymium metal is slightly in the nuclear regime, D /2 J =1.0002. In such case the nuclear specific heat is expected to show the narrowed Schottky type.