Grain boundary effects on the magneto-transport properties of Sr2FeMoO6 induced by variation of the ambient H2-Ar mixture ratio during annealing

Using the sol-gel method, polycrystalline double perovskites Sr2FeMoO6 with nanohleter-scale grain size have been synthesized in the ambience of a controlled stream of different gaseous H-2-Ar mixtures during annealing. X-ray diffraction (XRD) results indicated that with an increasing proportion of H-2, the component of the SrMoO4 impurity present in the crystallites first decreased, but then increased again with further increase of the H-2 proportion. The XRD results were further supported by independent sample analysis using Raman spectroscopy. Systematic investigation of the transport properties of the samples indicated that the SrMoO4 impurify at the grain boundary played a key role in determining the measured resistance and magnetoresistance of Sr2FeMoO6. This impurity effect was found to be correlated to the variation of the mixture ratio of the ambient H2-Ar gas stream surrounding the sample during annealing. (C) 2003 Elsevier Science B.V. All rights reserved.