  We study correlation effects and temperature dependencies in the electronic
structure of thin ferromagnetic local-moment films. In a first step the
Kondo-lattice model is investigated as a candidate for a proper representation
of local-moment ferromagnets. Magnetic and electronic key-quantities as the
Curie-temperature and the quasiparticle density of states are derived with
previously tested many-body procedures. It is shown that the magnetic
properties can be interpreted exclusively in terms of the temperature-dependent
electronic quasiparticle structure. An extended RKKY theory leads to effective
Heisenberg exchange integrals, which turn out to be functionals of the
conduction electron selfenergy, getting therewith a remarkable temperature and
band occupation dependence.
  In a second step the model studies are combined with tight binding-LMTO
bandstructure calculations in order to get for real ferromagnetic films
quasiparticle densities of states and quasiparticle bandstructures. The
proposed method avoids the double-counting of relevant interactions and takes
into account the correct symmetry of the atomic orbitals. Special results are
given for thin ferromagnetic EuO (100) films. The Curie temperature
$T_{\textrm{C}}$ of the EuO film turns out to be strongly thickness-dependent,
starting from a very low value ($\simeq 15K$) for the monolayer and reaching
the bulk value at about 30 layers. For a 20-layer film we predict the existence
of a surface state, the temperature-behaviour of which can lead to a surface
halfmetal-insulator transition.
