Negative ionic states of tin in the oxide superconductor Sr${}_{3-x}$SnO revealed by Mössbauer spectroscopy

Abstract

We report the temperature variation of the ${}^{119}$Sn-Mössbauer spectra of the antiperovskite (inverse perovskite) oxide superconductor Sr${}_{3-x}$SnO. Both superconductive (Sr-deficient) and non-superconductive (nearly stoichiometric) samples exhibit major $\gamma$-ray absorption with isomer shift similar to that of Mg${}_2$Sn. This fact shows that Sr${}_{3-x}$SnO contains the metallic anion Sn${}^{4-}$, which is rare especially among oxides. In both samples, we observed another $\gamma$-ray absorption with a larger isomer shift, indicating that there is another ionic state of Sn with a higher oxidation number. The temperature dependence of the absorption intensities reveals that the Sn ions exhibiting larger isomer shifts have a lower energy of the local vibration. The larger isomer shift and lower vibration energy are consistent with the values estimated from the first-principles calculations for hypothetical structures with various Sr-deficiency arrangements. Therefore, we conclude that the additional $\gamma$-ray absorptions originate from the Sn atoms neighboring the Sr deficiency.

10 pages, 7 figures

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• Topological Crystalline Insulators and Dirac Octets in Anti-perovskites
• Low-Energy Effective Hamiltonian and the Surface States of Ca_3PbO
• Evolution of Band Topology by Competing Band Overlap and Spin-Orbit Coupling: Twin Dirac Cones in Ba${}_3$SnO as a Prototype