Double perovskite Sr2FeMoO6−xNx (x=0.3, 1.0) oxynitrides with anionic ordering

► Synthesis and study of the new oxinitride double perovskites Sr2FeMoO6−xNx (x=0.3, 1.0). ► Compounds present anionic ordering between O and N. ► Nitridation process extraordinarily improves the long-range Fe/Mo ordering. ► We suggest a shift towards a configuration Fe4+(3d4, S=2):Mo5+(4d1, S=1/2).