Finding universal correlations between cationic disorder and low field magnetoresistance in FeMo double perovskite series

We search for general patterns that explain the low field magnetoresistance at low temperatures in the system A((2-x))A(x)'FeMoO6. The observed linear dependence of the low field magnetoresistance with the saturation magnetiz ation for the series is related to the antisite disorder at the Fe and Mo s ites. This is explained in terms of a spin dependent crossing of intragranu lar barriers originated from the presence of antiferromagnetic SrFeO3 patch es that naturally develop when antisite disorder occurs in the double perov skite. The presence of a moderate level of antisite disorder is at the very root of low field magnetoresistance although effects such as disorder dist ribution, connectivity, or morphology add their contribution.