Structural and magnetic properties of Sr2Fe1-xGaxMoO6 (0≤x≤0.25)

We have investigated the structure, magnetization and magnetoresistance (MR) of the double perovskite compounds Sr2Fe1-xGaxMoO6 (0 <= x <= 0.25). Rietveld refinement results show that the anti-site defects (ASDs) concentration increases with x, giving rise to highly disordered samples at the B/B' positions, for the highest doping levels. The evolution of bond lengths and ions oxidation states could be understood by the distribution of trivalent Ga ions at the B/B' positions, which leads to the formation of more disorder structure. The saturation magnetization and Curie temperature decreased with the Ga content increases in the samples, and their origin was found that the cations disorder for the Ga-doped compounds is annihilating double exchange mechanism due to the presence of significant amounts of Fe and Ga cations on the B' site. The low-field magnetoresistance of Sr2FeMoO6 (SFMO) can be greatly enhanced by replacing the Fe by the nonmagnetic Ga ion up to a temperature of 300 K, since Ga ions may act as a barrier for electron transport along the chain in the ferromagnetic segregation and weaken the ferromagnetic exchange. (c) 2006 Published by Elsevier B.V.