Effect of La doping on magnetotransport and magnetic properties of double perovskite Sr2FeMoO6 system

We have investigated the magnetotransport and magnetic properties on polycrystalline samples of Sr2−xLaxFeMoO6 (x=0x=0, 0.2, 0.4, 0.6, 0.8 and 1.0). The magnitude of intergrain tunneling magnetoresistance with low magnetic field of 0.88 T for x=0.2x=0.2 and 0.40.4 samples are as large as 5% and 7% at room temperature and 13% and 10% at 10 K, respectively. The increase of coercivity (HcHc), ratio of remanent magnetization with respect to saturation magnetization (Mr/MsMr/Ms), high saturation fields, and reduction of the saturation magnetization indicate that random disorder of spin orientation is mainly responsible for enhancement of the low-field magnetoresistance for samples with x⩽0.4x⩽0.4. Whereas rapid drop of HcHc, Mr/MsMr/Ms, MrMr, and saturation fields for samples with x>0.4x>0.4 signifies the growth of antiphase boundary, which gives rise to lower values of low-field MR.