Enhanced magnetoresistance in double perovskite Sr2FeMoO4 through SrMoO4 tunneling barriers

We synthesized the single phase Sr2FeMoO6 (sample B) and Sr2FeMoO6 with 10% SrMoO4 impurity phase (sample C) by sintering the material in different environments. Field emission scanning electron microscope (FE-SEM) and energy-dispersive X-ray analysis (EDAX) results clearly indicate that in sample C, the insulating SrMoO4 phase is segregated at the grain boundaries of Sr2FeMoO6 grains and produces the tunneling barriers in the conduction of charge carriers between SrFeMoO6 grains. X-ray diffraction (XRD) results show that generation of SrMoO4 phase increases the antisite defect in sample C. Both of the samples show semiconducting behaviour in the entire measured temperature range (80-300 K). The resistance of sample C is more as compared to sample B while the value of magnetization is less. The 38% enhancement in magnetoresistance (MR) at 80 K is observed for the sample C (having 10% insulating SrMoO4 phase) as compared to single phase sample B at 3 kOe. It is suggested that this enhancement in MR is due to intergrain tunneling through insulating nonmagnetic SrMoO4 grain boundary barriers in the Sr2FeMoO6 matrix and subsequent antisite defects, leading to enhancement in low field magnetoresistance (LFMR). This appears to be a simple way to produce tunneling barriers as compared to artificial fabrication of multilayer structures to enhance the low field magnetoresi stance. (c) 2007 Elsevier B.V. All rights reserved.