Influence of Fe segregation at grain boundaries on the magnetoresistance of Sr2Fe1+δMoO6 polycrystals

In this paper, we report the influence of Fe impurities on the magnetoresistance (MR) of double perovskite Sr2Fe1+delta MoO6 (0.00 <= delta <= 0.20) system. The significant Fe impurities have been created by two different approaches: one by adding the extra amount of Fe2O3 at starting of the synthesis and other by sintering the pristine Sr2FeMoO6 sample at high temperature (1300 degrees C) in high reducing environment (similar to 8% H-2 + 92% Ar). A remarkable 11% magnetoresistance at room temperature under the presence of low magnetic field (0.72 T) has been observed in the pristine sample. The achieved high low field magnetoresistance value in the sample may be due to the optimized synthesis conditions to get better inter-granular tunneling through grain boundaries. However, the presence of Fe impurity results into the sharp reduction in magnetoresistance because of reduced spin polarized tunneling. The loss of insulating nature of the grain boundaries and the inelastic scattering of the charge carriers through the metallic impurities of iron at grain boundaries may be the reason of reduced spin polarized tunneling. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4757026]