  New insights into the microscopic origin of itinerant ferromagnetism were
recently gained from investigations of electronic lattice models within
dynamical mean-field theory (DMFT). In particular, it is now established that
even in the one-band Hubbard model metallic ferromagnetism is stable at
intermediate values of the interaction U and density n on regular, frustrated
lattices. Furthermore, band degeneracy along with Hund's rule couplings is very
effective in stabilizing metallic ferromagnetism in a broad range of electron
fillings. DMFT also permits one to investigate more complicated correlation
models, e.g., the ferromagnetic Kondo lattice model with Coulomb interaction,
describing electrons in manganites with perovskite structure. Here we review
recent results obtained with DMFT which help to clarify the origin of
band-ferromagnetism as a correlation phenomenon.
