Simple Theory of the Magnetic Properties of Rare-Earth Metals

A simple theory for the magnetism of the rare-earth metals is presented. It is based on assuming strongly correlated, well-defined $f$-electron states of an atomiclike character which are weakly hybridized with conduction-band states. This hybridization plays the role of an indirect exchange interaction. A model calculation is presented: It yields for various values of the two relevant parameters ferromagnetic, antiferromagnetic, and helical arrangements. These arrangements are strongly dependent on the features of the conduction-electron band structure (Fermi surface). Order of magnitude estimates give reasonable agreement for physical parameters as determined from unrelated experiments.