Effect of Cu doping on the magnetoresistive behavior of double perovskite Sr 2FeMoO 6 polycrystals

Abstract

The electrical, magnetic, and transport properties of Cu-doped polycrystalline samples Sr 2Fe 1-xCu xMoO 6 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 Fe 3+ ions by Cu 2+ 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 Cu 2+ ions induces the occurrence of Fe 3+δ ions and the double exchange interaction in Fe 3+-O-Mo-O-Fe 3+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 Cu 2+ ions. Both the semiconductor-to-metal transition and the magnetoresistive behavior can be explained by the percolation threshold model. © 2002 American Institute of Physics. © 2002 American Institute of Physics.