Dynamical mean-field study of ferromagnetism in the periodic Anderson model

The ferromagnetic phase diagram of the periodic Anderson model is calculated using dynamical mean-field theory in combination with the modified perturbation theory. Concentrating on the intermediate valence regime, the phase boundaries are established as a function of the total electron density, the position of the atomic level, and the hybridization strength. The main contribution to the magnetic moment stems from the f electrons. The conduction-band polarization is, depending on the system parameters, either parallel or antiparallel to the f magnetization. By investigating the densities of states, one observes that the change of sign of the conduction-band polarization is closely connected to the hybridization gap, which is only apparent in the case of almost complete polarization of the f electrons. Finite-temperature calculations are also performed, and the Curie temperature as function of electron density and f-level position are determined. In the intermediate-valence regime, the phase transitions are found to be of second order.