Polarization of Fe(001) covered by MgO analyzed by spin-resolved x-ray photoemission spectroscopy

Single-crystalline (001) Fe thin films were prepared by molecular beam epitaxy and covered by epitaxial MgO barriers. The MgO growth was confirmed to be layer by layer as shown by reflection high-energy electron diffraction, which allowed us to prepare Fe films covered by only two atomic planes of MgO for spin polarization measurements. On the one hand, regular x-ray photoemission spectroscopy measurements evidenced a weak hybridization between Fe and O. Moreover, a large Fe magnetic moment at the interface with MgO was shown by x-ray magnetic circular dichroism measurements. These two observations are in agreement with theory. On the other hand, we show that the Fe density of states can be measured by photoemission through the oxide barrier, since the oxide valence band only starts at 4 eV below the Fermi level. Spin-resolved x-ray photoemission measurements performed at ESRF allowed us to demonstrate that the electrons emitted from the (001) Fe layer through the barrier are polarized. A polarization fully integrated in k space and corrected from remanence near 42% was measured.