Eu valence in ultra-thin layers of EuF3 derived from photon energy dependent photoemission and photoabsorption

X-ray absorption (XAS) and resonant photoemission (RESPE) have been used to study Eu valence in ultra-thin EuF3 layers grown by MBE. It was shown that resonant photoemission (RESPE) from EuF3 ultra-thin layers exhibits different features for photon energies close to the 4d–4f threshold (130–150 eV) and the 3d–4f excitation region (1120–1170 eV). For the low energy resonance a clear effect of resonance induced Eu2+ states (final state 4f6) has been found whereas no divalent Eu states have been observed when photon energy was tuned to the 3d–4f transition. Our results indicate that Eu valence derived from the XAS and RESPE spectra depends on photon energy and is dominated by the final state effects for the 4d–4f resonance. An explanation is given based on the screening effect and different decay channels of the 4d–4f and 3d–4f resonances.