Structural, magnetic and transport properties of Sr2Fe1−xMgxMoO6(0⩽x⩽1) double perovskites

A series of Sr2Fe1−xMgxMoO6(0⩽x⩽1) double perovskite oxides have been prepared and their crystal, magnetic and transport properties studied. Rietveld refinements, in tetragonal space group I4/m, show an almost complete B-cation ordering in the doped samples. A systematic decrease in Curie temperature, TC and saturation magnetization, MS with increase of x has been observed in this solid solution series. Resistivities show a semiconducting behavior for all samples and increase with x. The x=0 sample becomes metallic above a metal-insulator transition temperature of 45 K in applied fields of 30 and 50 kOe. Negative colossal magnetoresistances (CMR) have been observed (up to 47% for the x=0.6 sample at 5 K) in all the samples and these MR effects show a strong dependence on the microstructural nature (grain boundaries) of the material.