Unusual electronic state of tin dopant atoms in surface layers of NiTiO3

The 119 Sn Mössbauer spectra of polycrystalline NiTiO 3 samples impregnated with a solution containing 0.3 at % Sn 4+ are evidence that annealing in H 2 converts tin into the state with the electron density |Ψ(0)| 2 on 119 Sn nuclei corresponding to “Sn 3+ ” ions. The stabilization of tin atoms in such an untypical formal oxidation state occurs at a depth of no more than 2–3 nm from the surface of titanate crystallites. It was revealed that the Sn 3+ ions are not subjected to spin polarization even at temperatures considerably lower than the Néel temperature of NiTiO 3 , which can be explained by their location in the Ni 2+ positions. The formation of Sn3+ prevents the further reduction of tin to the divalent state and, hence, precludes localization of 119 Sn probe cations in positions at the interface.