New approach for electronic and nuclear magnetism of singlet ground state systems

Abstract

A new approach is presented to deal with magnetic properties of the singlet ground state systems with nuclear spins of arbitrary magnitude. The electronic spin polarisation of a magnetic atom consists of the exchange-induced part and the HF-induced part. The latter is assumed to follow adiabatically the nuclear spin of the interested atom and gives rise to the I-I coupling and the pseudoquadrupole interaction while the former is responsible for the internal field effect to nuclear spins. The new method succeeds in constructing the effective nuclear spin Hamiltonian in such a scheme and treating the problem by taking the nuclear spin polarisation as the representative LRO parameter. It gives a unified treatment of magnetism over all regimes (electronic and nuclear regimes) and phases (ordered and paramagnetic states) irrespective of relative magnitudes of the parameters in the Hamiltonian. Some numerical results of the present formalism are presented.