Tunnelling magnetoresistance of double perovskite Sr_2FeMoO_6 enhanced by grain boundary adjustment

摘要

Polycrystalline double perovskite Sr_2FeMoO_6 samples were synthesized by a wet chemistry method under controlled reduction conditions. Single-phase 'bulrush-like' samples of grain size about 110 nm in width and >2 mu m in length were readily obtained at temperatures as low as 950 deg C, and they showed a large room-temperature tunnelling magnetoresistance (DELTA rho/rho_0) of -21 percent at a low magnetic field of 10 kOe. Utilizing the reactivity of Sr_2FeMoO_6 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 percent. 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.