Combined effect of hybridization and exchange Coulomb interaction on magnetic ordering in correlated-f-electron cerium systems

The model Hamiltonian describing the partially delocalized $f$-electron system has been generalized to include both hybridization and band-$f$ exchange Coulomb interaction. A method has been developed to calculate the parameters appearing in such a model Hamiltonian from first principles. This enables us to calculate $f$-electron-based electronic and magnetic phenomena of pertinent materials on a quantitative basis. Calculations have been done for cerium monopnictides and monochalcogenides. Results are in agreement with experiment on various unusual behaviors of these materials, such as anomalous crystalfield splitting and anisotropic magnetic ordering, all of which are caused by the interactions between $f$ electrons and band electrons. In contrast to the earlier version of this theory that included only hybridization effects and produced range parameters (two-ion "exchange" coupling) that failed by an order of magnitude in matching the phenomenologically determined parameters which provide agreement with experiment, the present first-principles theory calculations which also include band-$f$ Coulomb exchange provide excellent agreement with the phenomenologically required magnitude.