We introduce a new approach to the periodic Anderson model (PAM) that allows
a detailed investigation of the magnetic properties in the Kondo as well as the
intermediate valence regime. Our method is based on an exact mapping of the PAM
onto an effective medium strong-coupling Hubbard model. For the latter, the
so-called spectral density approach (SDA) is rather well motivated since it is
based on exact results in the strong coupling limit. Besides the T=0 phase
diagram, magnetization curves and Curie temperatures are presented and
discussed with help of temperature-dependent quasiparticle densities of state.
In the intermediate valence regime, the hybridization gap plays a major role in
determining the magnetic behaviour. Furthermore, our results indicate that
ferromagnetism in this parameter regime is not induced by an effective
spin-spin interaction between the localized levels mediated by conduction
electrons as it is the case in the Kondo regime. The magnetic ordering is
rather a single band effect within an effective f-band.Comment: 13 pages, 16 figures, Phys. Stat. Sol. in pres