Synthesis, crystal structure, and magnetic properties of a novel layered manganese oxide Sr2MnGaO5+δ

A. M. Abakumov, M. G. Rozova, B. Ph Pavlyuk, M. V. Lobanov, E. V. Antipov, O. I. Lebedev, G. Van Tendeloo, O. L. Ignatchik, E. A. Ovtchenkov, Yu A. Koksharov, A. N. Vasil'ev

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55 Citations (Scopus)

Abstract

New Sr2MnGaO4.97 complex oxide was synthesized by solid state reaction in sealed silica tubes at 950-1000°C. The Sr2MnGaO4.97 crystal structure was refined from X-ray powder diffraction data. Sr2MnGaO4.97 is based on the Ima2 brownmillerite-type structure with apically elongated MnO6 octahedra due to a Jahn-Teller effect. Electron diffraction and high-resolution electron microscopy showed that local ordering of the left- and right-hand chains of GaO4 tetrahedra in Sr2MnGaO4.97 leads to a superstructure with a doubling of the b parameter of the orthorhombic unit cell. The formal oxidation state of Mn (VMn) can be varied by thermal treatments at elevated oxygen pressure (450°C, 20 bar of O2). The oxygen insertion induces a structure transformation in oxidized Sr2MnGaO5.47 material with the formation of a tetragonal perovskite-like structure (a ≈ ap, c ≈ 2cp) with oxygen vacancies located in the Ga layers. The oxidation is accompanied by a significant compression of the Mn-O apical distances and a suppression of the Jahn-Teller deformation. Both Sr2MnGaO4.97 and Sr2MnGaO5.47 can probably be treated as canted antiferromagnets with TN∼150 and 80 K, respectively.

Original languageEnglish
Pages (from-to)353-361
Number of pages9
JournalJournal of Solid State Chemistry
Volume160
Issue number2
DOIs
Publication statusPublished - 2001
Externally publishedYes

Keywords

  • Crystal structure
  • Oxygen nonstoichiometry
  • SrMnGaO
  • Synthesis

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