ELECTRONIC QUASI-PARTICLE STRUCTURE OF A THIN FERROMAGNETIC LOCAL-MOMENT FILM

The electronic quasiparticle energy spectrum of a ferromagnetic thin f ilm is investigated within the framework of the s-f model. Exact resul ts are derived for the special situation of a single electron in an ot herwise empty energy band being exchange coupled to a ferromagneticall y ordered localized spin system (EuO, EuS). While the up-spin spectrum does not show any striking correlation effects, the down-spin spectru m is non-trivial due to different kinds of spin exchange processes. Re peated emission and reabsorption of a magnon by the down arrow-electro n can result in an effective electron-magnon attraction giving rise to a polaron-like quasiparticle ('magnetic polaron'). Direct emission of a magnon by the I-electron without reabsorption produces a rather bro ad 'scattering part' in the spectral density. We assume a s.c. film co nsisting of n layers parallel to the (100) surface. The mutual influen ce of correlation effects and the reduced symmetry of the film is work ed out in detail by inspecting spectral densities and local quasiparti cle densities of states.