A heavy-fermion state with singular density of states

The metamagnetic behavior of CeRu2Si2 and the non Fermi-liquid behavior of CeNi2Ge2 are described by the periodic Coqblin-Schrieffer model with anisotropic c-f exchange interaction in the mean-field theory. Only the Kramers doublet of M-J = +/-5/2 for the 4f states of Ce ions is considered, for the case of which the density of quasi-particle states has singularity of \omega\(-1/2) around the effective f-level energy. In the asymmetric case applicable to CeRu2Si2, the chemical potential reaches the singularity at a finite magnetic field, at which the magnetization shows a metamagnetic-like increase. On the other hand, in the symmetric case applicable to CeNi2Ge2: the chemical potential is on the singularity at zero magnetic field, and non-Fermi-liquid-like behaviors emerge in the susceptibility and the specific heat.