Unusual Electronic State of Tin Dopant Atoms
in Surface Layers of NiTiO₃

R. A. Astashkin^a, M. V. Korolenko^a, M. I. Afanasov^a, P. B. Fabrichnyi^a,
A. Wattiaux^b, C. Labrugère^b, and C. Delmas^b

^a Moscow State University, Leninskie gory, Moscow, 119992 Russia

^b Institut de la Chimie de la Matière Condensée de Bordeaux, Université Bordeaux 1,
CNRS-UPR 4048, Avenue Dr. A. Schweitzer 33608 Pessac, Cedex, France

Received May 5, 2010

Abstract—The ¹¹⁹Sn Mössbauer spectra of polycrystalline NiTiO₃ samples impregnated with a solution con-
taining 0.3 at % Sn⁴⁺ are evidence that annealing in H₂ converts tin into the state with the electron density (0)²
on ¹¹⁹Sn nuclei corresponding to “Sn³⁺” ions. The stabilization of tin atoms in such an untypical formal oxida-
tion state occurs at a depth of no more than 2–3 nm from the surface of titanate crystallites. It was revealed that
the Sn³⁺ ions are not subjected to spin polarization even at temperatures considerably lower than the Néel tem-
perature of NiTiO₃, which can be explained by their location in the Ni²⁺ positions. The formation of Sn³⁺ pre-
vents the further reduction of tin to the divalent state and, hence, precludes localization of ¹¹⁹Sn probe cations
in positions at the interface.

DOI: 10.1134/S0036023611040048

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