THE THEORY OF THE MAGNETIZATION PROCESS IN CERU2SI2

A metamagnetic-like transition has been reported by Haen et al (1987) for the magnetization curve in CeRu2Si2 with a large anisotropy. We introduce here a weakly interacting Kondo model, including crystalline field splitting, which is composed of a collection of SU(N(c)) Kondo models and a RKKY interaction between the localized spins of the Ce ions. We investigate to what extent the metamagnetic-like behaviour can appear on the basis of this simplified model. The model has the advantage that we can derive the effective single site SU(N(c)) Kondo Hamiltonian with the use of the mean field approximation for the intersite coupling. Then, using the exact solution of the effective Hamiltonian, we investigate the magnetization process of the ground state. With the set of appropriate crystalline field parameters determined from the analysis of the specific heat, we have obtained the metamagnetic-like transition at a reasonable magnetic field with the large anisotropy qualitatively in agreement with the experimental data of CeRu2Si2. However, to achieve this it was necessary to use a large Kondo temperature and a ferromagnetic RKKY interaction. These discrepancies may be traced back to the mean field approximation for the intersite correlations.