Influence of Oxygen Stoichiometry and Cation Ordering on Magnetoresistive Properties of Sr2FeMoO6±δ

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This work investigates the influence of initial compound synthesis prehistory on the phase sequence during formation of single-phase Sr2FeMoO6 (SFMO). Analytical-grade SrCO3, Fe2O3 and MoO3 (sample No.1) and partially reduced precursors of SrFeO3-x (SFO) and SrMoO4-y (SMO) (sample No.2) were used as initial reagents. In the latter case, kinetic limitations of SFMO phase formation are resolved by increasing the diffusivity of both of Fe3+ and Mo5+ and decreasing diffusion lengths to the reaction zone. This enhances the double-perovskite growth rate, lowers synthesis temperature and increases the intensity of X-ray reflections of (011) and (013) planes suggesting a superstructural ordering of Fe3+ and Mo5+ cations. Samples No.1 and No.2 have both a Тс ~ 420K while the magnetization value at 77 K in the sample No.2 is higher by a factor 2.3 compared to that of sample No.1. A decrease of the oxygen vacancy concentration by annealing Sr2FeMoO5.82 lowered magnetization of the samples and promoted the formation of a second magnetic phase with Тс = 700 К. We suppose that an increase of oxygen partial pressure during annealing causes formation of clusters with antiferromagnetic coupling in Fe3+-О2--Fe3+ chains. In order to increase the magnetoresistive effect at temperatures relevant for technical application, weak intergrain bonds should be formed.

Info:

Periodical:

Materials Science Forum (Volumes 636-637)

Edited by:

Luís Guerra ROSA and Fernanda MARGARIDO

Pages:

338-343

DOI:

10.4028/www.scientific.net/MSF.636-637.338

Citation:

M. Kalanda et al., "Influence of Oxygen Stoichiometry and Cation Ordering on Magnetoresistive Properties of Sr2FeMoO6±δ", Materials Science Forum, Vols. 636-637, pp. 338-343, 2010

Online since:

January 2010

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$35.00

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