57Fe Mössbauer spectroscopy studies of Sr2Fe1−xCrxMo1−xWxO6 double perovskite compounds

Polycrystalline double perovskites Sr2Fe1−x Cr x Mo1−x W x O6 with x=0, 0.05, 0.10, 0.15, 0.20, and 0.30 have been prepared by sold state reactions. A continuous decrease of the tetragonal unit cell parameters α and c with increasing x values is observed. The highest Curie temperature T c =426 K is recorded for the x=0.10 compound. 57Fe Mossbauer spectroscopy measurements indicate a non-integral electronic configuration of ≈3d5.3 for the Fe ions at the ordered double perovskite structure for x≤0.20, which reaches ≈3d5.4 for x=0.30. Fe-Mo/W anti-site and anti-phase boundary defects are observed in all samples in equal concentrations of around 3% of the total number of Fe ions in their structure.