Thermodynamics of intermediate-valence two-band ferromagnets: Magnetic properties

We present the influence of the finite bandwidth of the 4f (5f) band and finite intrasite Coulomb repulsion on the magnetic properties of the generalized s-f model. The calculation of the Curie temperature T-C shows that the increase of the 4f (5f) bandwidth suppress the magnetic phase and can completely destroy it. The increase in the Coulomb intrasite repulsion acts in the opposite direction. The mechanism of indirect exchange interaction is discussed in detail to explain the shapes of the T-C dependence on different model parameters. The calculated T-C dependence on the average occupation number or on the position of the 4f (5f) level shows great similarities to the experimentally measured T-C curves versus applied pressure or dopant concentration in many intermediate-valence rare-earth or actinide compounds and alloys.