Ferromagnetic EuS films: Magnetic stability, electronic structure, and magnetic surface states

We present the temperature- and layer-dependent electronic structure of a 20-layer EuS(100) film using a combination of first-principles and model calculations, the latter based on the ferromagnetic Kondo lattice. The calculated thickness-dependent Curie temperature agrees very well with experimental data. The projected $5d$ band structure is at finite temperatures strongly influenced by damping effects due to spin-exchange processes. Spin-split unoccupied $5d$-surface states are found with a Stoner-like collapsing for increasing temperature towards the Curie point and with an exponential decay of spectral weight with increasing distance from the surface.