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Perovskite and Pyrochlore Modifications of Pb2MnReO6: Synthesis, Structure, and Electronic Properties

Ramesha, K and Sebastian, L and Eichhorn, B and Gopalakrishnan, J (2003) Perovskite and Pyrochlore Modifications of Pb2MnReO6: Synthesis, Structure, and Electronic Properties. In: Chemistry Of Materials, 15 (3). pp. 668-674.

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We describe the synthesis and investigations of Pb2MnReO6 in perovskite and pyrochlore modifications. Both theb modifications are formed at atmospheric pressure, the perovskite (1) at 550 degreesC and the pyrochlore (II) at 600 degreesC. Rietveld refinements of the structures using the powder XRD data show that oxide I adopts the monoclinic (P2(1)/n) double perovskite structure with partial ordering (similar to72%) of Mn-II/Re-VI at the octahedral sites, while oxide II crystallizes in a defect-pyrochlore structure where Mn(II/)Rev(I) are disordered at the octahedral sites. The frustrated cation sublattice precludes a long-range ordering of Mn/Re in the pyrochlore structure. I is a semiconductor showing evidence for a ferrimagnetic ordering at T-c similar to 100 K, but the small saturation magnetic moment ([S] = 0.81) and the divergence between FC and ZFC magnetization data are consistent with spin-glass-like behavior and a partially ordered Mn/Re in the double perovskite structure. On the other hand, both the Curie-Weiss paramagnetism down to similar to5 K and non-Arrhenius electrical resistivity behavior of II suggest a spin-liquid/spin-glass ground state that is consistent with the frustrated cation sublattice, of the pyrochlore structure.

Item Type: Journal Article
Publication: Chemistry Of Materials
Publisher: American Chemical Society
Additional Information: Copyright of this article belongs to American Chemical Society.
Department/Centre: Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited: 04 Nov 2009 09:09
Last Modified: 19 Sep 2010 04:56
URI: http://eprints.iisc.ac.in/id/eprint/17253

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