Influence of Al-substitution on structures, resistivity and magnetic properties of LaxSr(2−x)Fe(1+y)Mo(1−y)O6 (x=3y, y=0.05, 0.1, 0.15, 0.2)

Two series of single-phased LaxSr(2−x)Fe(1+y)Mo(1−y)O6 and LaxSr(2−x)Fe(1+0.5y)Al0.5yMo(1−y)O6 (x=3y, y=0.05, 0.1, 0.15 and 0.2) double perovskites were prepared by solid-state reaction. The effects of Al-substitution on the structures, resistivity and magnetic properties of LaxSr(2−x)Fe(1+y)Mo(1−y)O6 were investigated. Although Al-replacement exhibits a negligible influence of on the B-site ordering degree, it results in the suppression of magnetisation caused by non-magnetic Al3+ ions. Reduction of grain sizes leads to increased resistivity, thus an optimised magnetoresistance (MR) behaviour is observed. The greatest MR extent improvement can be obtained when y is 0.15 and the MR% of the Al-doped ceramics reaches −10.5% (10 K, 1 T), which is 2 times greater than that of the undoped ceramics (−4.6%, 10 K, 1 T). Interestingly, the Curie temperature (Tc) of both Al-doped and undoped samples maintained relatively constant values of approximately 420 K and 405 K, respectively, which were different results from the data obtained for similar electron-doping systems in the literature.