The influence of structural disorder on the magnetic properties of Sr2Fe1 – xGaxTaO6 (0 ≤ x ≤ 1)

Powder samples of the magnetically diluted cubic perovskite phases Sr2Fe1 − xGaxTaO6 have been prepared by high temperature ceramic methods. X-Ray powder diffraction data show that the cations occupying the 6-coordinate site are chemically disordered in the range 0.10 ≤ x ≤ 0.40 and that increasing the Ga3+ concentration above this value leads to partial cation ordering between Ga3+ and Ta5+. Magnetic susceptibility data collected from these compounds can be fitted to the Curie–Weiss law, resulting in estimates of the magnetic moment per Fe3+ cation of between 4.57(1) (x = 0.20) and 6.37(1) μB (x = 0.90). The cause of the unexpectedly low paramagnetic moment observed in most of these compositions is ascribed to the effect of superexchange interactions extending beyond the adjacent 6-coordinate sites in the simple cubic lattice.