  Electronic and structural properties of ultrathin MgO layers grown on
epitaxial Fe(110) films were investigated at room temperature by means of
spin-resolved photoelectron spectroscopy, Auger-electron spectroscopy, and low
energy electron diffraction. The spin polarization at the Fermi level of the
Fe(110) film decreases abruptly with increasing thickness of MgO layer up to 7
\AA. This behavior is attributed to the formation of a thin FeO layer at the
MgO(111)/Fe(110) interface, attenuating the intrinsic spin polarization.
