Enhanced intergrain tunneling magnetoresistance in double perovskite Sr2FeMoO6 polycrystals with nanometer-scale particles

Polycrystalline ordered double perovskite Sr2FeMoO6 bulk samples with grain size in the range of 29-45 nm have been synthesized at temperatures from 9 00 to 1000 degrees C, using a sol-gel method. We find that the intergrain m agnetoresistance is closely correlated with the grain size. The sample with the grain size of 29 nm shows large magnetoresistance Delta rho/rho(0), 30 %-20% at a low magnetic field of 4 kG over a wide temperature range from 20 to 300 K. The results can be explained in terms of spin-dependent intergra in tunneling model. (C) 1999 American Institute of Physics. [S0003-6951(99) 02050-1].