Magnetism of a “Nuclei Plus Electrons” System

Nuclear magnetism is discussed for a system in which each nuclear spin interacts only with electrons on the same atom by the hyperfine interaction, the electrons having the singlet ground state and interacting with an appreciable exchange interaction. As the exchange interaction approaches to the threshold value to induce a spontaneous electron spin ordering, the Curie temperature of the “ nuclear spin ordering ” and the “ nuclear contribution ” to the paramagnetic susceptibility are both raised by the electron exchange enhancement factor and an appreciable electron spin polarization is also induced. There is collective mode of mainly electron spin nature and of mainly nuclear spin nature. The energy gaps at q =0 in their dispersions are obtained in some typical cases.