Spin-waves in itinerant ferromagnets

We introduce a novel approach for the investigation of spin-wave excitation s in itinerant ferromagnets. Our theory is based on a variational treatment of general multi-band Hubbard models which describe elements and compounds of transition metals. The magnon dispersion is derived approximately as th e energy of a variational spin-wave state in the limit of large spatial dim ensions. A numerical evaluation of our results is feasible for general mult i-band models. As a first application we consider a model with two degenera te orbitals per lattice site. From our results we can conclude that spin-wa ve excitations in strong itinerant ferromagnets are very similar to those i n ferromagnetic spin systems.