Possible Deviation from SU(4) Symmetry of the RKKY Interaction in CeB₆

Abstract

In order to determine a proper RKKY interaction model for CeB₆, the general model Hamiltonian for Γ₈ quartet with nearest-neighbor interactions is investigated in terms of the constant coupling approximation (CCA). In contrast with the mean field approximation, any antiferro multipolar ordering becomes unstable near SU(4) symmetry due to fluctuation of interactions taken into account in the CCA as pair correlations. A semiquantitative explanation of the antiferro-quadrupolar transition temperature and the specific heat in phase I of CeB₆ is obtained in a case that the coupling constants of interactions between various moments are quite different each other. It is therefore possible that an RKKY interaction model proper for CeB₆ deviates considerably from SU(4) symmetry.