D. Meyer et al., FERROMAGNETISM WITHIN THE PERIODIC ANDERSON MODEL - A NEW APPROXIMATION SCHEME, Physica status solidi. b, Basic research, 208(2), 1998, pp. 473-495
We introduce a new approach to the periodic Anderson model (PAM) that
allows a detailed investigation of the magnetic properties in the Kond
o as well as the intermediate valence regime. Our method is based on a
n exact mapping of the PAM onto an effective medium strong-coupling Hu
bbard model. For the latter, the so-called spectral density approach (
SDA) is rather well motivated since it is based on exact results in th
e 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 interm
ediate valence regime, the hybridization gap plays a major role in det
ermining the magnetic behaviour. :Furthermore, our results indicate th
at ferromagnetism in this parameter regime is not induced by an effect
ive spin-spin interaction between the localized levels mediated by con
duction electrons as it is the case in the Kondo regime. The magnetic
ordering is rather a single-band effect within an effective f-band.