Effects of iron substitution and anti-site disorder on crystal structures, vibrational, optical and magnetic properties of double perovskites Sr2(Fe1−xNix)TeO6
x )TeO 6 ( x = 0, 0.25, 0.50, 0.75, and 1) has been synthesized in polycrystalline form by solid-state reaction at 1300 K in air. Their crystal structures were probed by powder X-ray diffraction at room [...] of samples with compositions x = 0, 0.25, 0.50 and 0.75 reveal the presence of Fe 3+ in high-spin state with an anti-site disorder of Fe–Ni–Te cations in distorted octahedral environments (site 2 d and [...] between FC and ZFC curves for all compositions has been observed. The results show that the ground states of the doped materials might be spin glasses or magnetically ordered.