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The structural, magnetic and electronic properties of the double perovskite series Sr2FeMo1−xWxO6, where x = 0, 0.1, 0.2, 0.3 and 0.4, are investigated using x-ray diffraction, Mössbauer spectroscopy and magnetization measurements. The crystal structure has been studied at 450 K and at room temperature. There is a structural transition from tetragonal to cubic for x ≤ 0.2. The Curie temperature (TC) shows a slight increase for x = 0.1 and 0.2 (TC = 435 and 432 K, respectively), compared to the value (TC = 415 K) of the x = 0 end member. The largest magnetoresistance at 300 K was found for the x = 0 and 0.2 compounds. The concentration of antisite defects determined by Mössbauer spectroscopy and x-ray analysis indicate that: (i) cation ordering at the B sites improves with increasing W content and (ii) the antisite defects formed in the B sites of the double perovskite structure do not aggregate to form bigger intragrain clusters with different local chemical compositions. The x dependence of the magnetic moment, which exceeds 4μB per formula unit when x > 0.3, is explained in a ferrimagnetic model with, respectively, antiparallel and parallel coupling of antisite iron and molybdenum to their iron or molybdenum cation neighbours. There is a small contribution of 0.2 μB/W to the ↓ sublattice moment. The W-containing materials are not half-metallic.

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