Tunnelling magnetoresistance of double perovskite Sr2FeMoO6 enhanced by grain boundary adjustment

Polycrystalline double perovskite Sr2FeMoO6 samples were synthesized by a wet chemistry method under controlled reduction conditions. Single-phase 'bulrush-like' samples of grain size about 110nm in width and > 2 mu m in length were readily obtained at temperatures as low as 950 degrees C, and they showed a large room-temperature tunnelling magnetoresistance (Delta rho/rho(0)) of -21% at a low magnetic field of 10 kOe. Utilizing the reactivity of Sr2FeMoO6 to water and a sonochemical technique, we manipulated the properties of grain boundary (GB) barriers, and managed to enhance the room-temperature tunnelling magnetoresistance to -35%. The magnitude of the low-field magnetoresistance appears to depend strongly on GB properties, and can be regulated by controlling the reaction time with water.