Influence of band and orbital degeneracies on ferromagnetism in the periodic Anderson model

We investigate the influence of degeneracies of the conduction band and the f orbital on the stability of ferromagnetism in the periodic Anderson model. To this end we calculate the temperature dependence of the inverse susceptibility for different degeneracies, D(c) and D(f), and conduction-electron densities n(c) within the dynamical mean-field theory. A strong increase in the Curie temperature T(C) with the degeneracy D(f) of the localized f level is found. For D(c)<= D(f) a simple ansatz based on a mean-field treatment of the Ruderman-Kittel-Kasuya-Yoshida interaction is shown to imply a scaling behavior of T(C) as a function of the conduction-electron density per band which is well obeyed by the numerical results. In particular, T(C) is found to have a maximum at n(c)/D(c)approximate to 0.3.