Evidence of charge disproportionation on the nickel sublattice in EuNiO3 thin films: X-ray photoemission studies

Photoelectron spectroscopy studies of correlated electron EuNiO3 compound have revealed a significant temperature dependence of Ni 2p multiplets. In particular, clear evidence of Ni 2p multiplet splitting is reported not only below the metal-insulator transition (MIT), as expected, but also, although smaller in magnitude, above MIT. This electronic anomaly has been ascribed to charge disproportionation associated to NiO6 octahedra distortion taking place in the perovskite structure. The strongly debated model of dynamic charge fluctuations with temperature-dependent amplitude seems to fit the best to the observed behavior reported here.