  Pulse laser deposited La2/3Sr1/3MnO3 ultrathin films on SrTiO3 substrates
were characterized by polar and longitudinal Kerr magneto-optical spectroscopy.
An agreement between experimental and theoretical spectra was achieved for a
10.7 nm thick film, while a distinction in the Kerr effect amplitudes was
obtained for a 5 nm thick film. This points to the slight suppression of
ferromagnetism by interface effects. Nevertheless, the room temperature
ferromagnetism of the 5 nm thick film was clearly demonstrated. All the studied
films exhibit magneto-optical properties similar to single crystals and thick
films, which confirms a fully developed perovskite structure even at 5 nm.
