Size dependence of electronic and magnetic properties of double- perovskite Sr2FeMoO6

Sr2FeMoO6 samples with different grain sizes were prepared by the sol–gel method. X-ray diffraction (XRD) patterns and field-emission scanning electron microscopy (FE-SEM) of the Sr2FeMoO6 samples show that the samples are in the nanometer range. The average grain sizes DD for these samples are 34.5, 39.7 and 44.3 nm, increasing with the sintering temperature. The transport measurements show that the Sr2FeMoO6 samples behave like semiconductors at low temperatures, dominated by the carrier scattering at the grain boundaries (GBs). And the resistivities of the samples are 1.6, 1.2 and 0.5 mΩ cm at 10 K, respectively, increasing with decreasing grain size. The temperature dependences of the magnetization and resistance clearly demonstrate the coexistence of ferromagnetic metal and antiferromagnetic (or paramagnetic) insulator, which is believed to induce a metal–insulator transition at the Curie temperature (TC)(TC).