  Heusler compounds are promising materials for spintronics with adjustable
electronic properties including 100% spin polarization at the Fermi energy. We
investigate the electronic states of AlOx capped epitaxial thin films of the
ferromagnetic half metal Co2MnSi ex-situ by soft X-ray angular resolved
photoemission spectroscopy (SX-ARPES). Good agreement between the experimental
SX- ARPES results and photoemission calculations including surface effects was
obtained. In particular, we observed in line with our calculations a large
photoemission intensity at the center of the Brillouin zone, which does not
originate from bulk states, but from a surface resonance. This provides strong
evidence for the validity of the previously proposed model based on this
resonance, which was applied to explain the huge spin polarization of Co2MnSi
observed by angular-integrating UV-photoemission spectroscopy.
