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Synthesis, Crystal Structure, and Magnetic Properties of a Novel Layered Manganese Oxide Sr2MnGaO5+δ

✍ Scribed by 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

Publisher
Elsevier Science
Year
2001
Tongue
English
Weight
814 KB
Volume
160
Category
Article
ISSN
0022-4596

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✦ Synopsis

New Sr 2 MnGaO 4.97 complex oxide was synthesized by solid state reaction in sealed silica tubes at 950+10003C. The Sr 2 MnGaO 4.97 crystal structure was re5ned from X-ray powder di4raction data. Sr 2 MnGaO 4.97 is based on the Ima2 brownmillerite-type structure with apically elongated MnO 6 octahedra due to a Jahn+Teller e4ect. Electron di4raction and high-resolution electron microscopy showed that local ordering of the leftand right-hand chains of GaO 4 tetrahedra in Sr 2 MnGaO 4.97 leads to a superstructure with a doubling of the b parameter of the orthorhombic unit cell. The formal oxidation state of Mn (V Mn ) can be varied by thermal treatments at elevated oxygen pressure (4503C, 20 bar of O 2 ). The oxygen insertion induces a structure transformation in oxidized Sr 2 MnGaO 5.47 material with the formation of a tetragonal perovskite-like structure (a+a p , c+2c p ) with oxygen vacancies located in the Ga layers. The oxidation is accompanied by a signi5cant compression of the Mn+O apical distances and a suppression of the Jahn+Teller deformation. Both Sr 2 MnGaO 4.97 and Sr 2 MnGaO 5.47 can probably be treated as canted antiferromagnets with T N &150 and 80 K, respectively.

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