Effect of Cu doping on the magnetoresistive behavior of double perovskite Sr2FeMoO6 polycrystals

The electrical, magnetic, and transport properties of Cu-doped polycrystalline samples Sr2Fe1−xCuxMoO6 with ordered double perovskite structure have been investigated systematically. Analysis of the x-ray powder diffraction pattern based on the Rietveld analysis indicates that the substitution of Fe3+ ions by Cu2+ ions enhances the site location order of Fe, Cu, and Mo on the B site for the high-doping-level samples (x=0.20, 0.25, 0.30). With increasing doping level, a transition from semiconductor to metal behavior was also found to occur. Furthermore, the transition temperature was found to decrease either by the application of a magnetic field or by increasing the doping level. It can be concluded that the existence of Cu2+ ions induces the occurrence of Fe3+δ ions and the double exchange interaction in Fe3+–O–Mo–O–Fe3+δ. The transport mechanism in these samples can be attributed to the competition between the metal phase and the semiconductor phase arising from the doping of Cu2+ ions. Both the semico...