Abstract
Magnetic susceptibility in a heavy fermion system is composed of the Pauli term (χP) and the Van-Vleck term (χV). The latter comes from the interband excitation, where f-orbital degeneracy is essential. In this work, we study χP and χV in the orbitally degenerate (J=5/2) periodic Anderson model for both the metallic and insulating cases. The effect of the correlation between f-electrons is investigated using the self-consistent second-order perturbation theory. The main results are as follows. (i) Sixfold degenerate model: both χP and χV are enhanced by a factor of 1/z (z is the renormalization constant). (ii) Nondegenerate model: only χP is enhanced by 1/z. Thus, orbital degeneracy is indispensable for the enhancement of χV. Moreover, orbital degeneracy reduces the Wilson ratio and stabilizes the nonmagnetic Fermi liquid state.
