Effective Nuclear Spin Hamiltonian for Magnetically Ordered Singlet Ground State System

Abstract

The effective nuclear spin Hamiltonian is derived for the system where magnetic ions have the electronic singlet ground state and are in a magnetically ordered state. As in the nuclear regime, the effective Hamiltonian involves the I - I coupling, the pseudo-nuclear quadrupole interaction, the pseudo-nuclear Zeeman energy, which are all exchange-enhanced, in addition to the internal field term due to the ordered electron spins. The exchange enhancement factor may be different from that in the paramagnetic state. The recent experimental data on Pr 3 Tl are discussed in terms of the effective Hamiltonian.