Magnetic interactions and magnetic anisotropy in exchange coupled 4f-3d systems: A case study of a heterodtoudear Ce

We report here a detailed single-crystal EPR and magnetic study of a homologous series of complexes of the type Ln-M (Ln=La-III, Ce-III; M= Fe-III, Co-III). We were able to obtain a detailed picture of the low-lying levels of Ce-III and Fe-III centres through the combined use of single-crystal EPR and magnetic susceptibility data. We show that classical ligand field theory can be of great help in rationalising the energies of the low-lying levels of both the transition-metal and rare-earth ions. The combined analysis of single-crystal EPR and magnetic data of the coupled system Ce-Fe confirmed the great complexity of the interactions involving rare-earth elements. With little uncertainty, it turned out clearly that the description of the interaction involving the lowest lying spin levels requires the introduction of the isotropic, anisotropic and antisymmetric terms.