Tunnelling magnetoresistance of double perovskite Sr₂FeMoO₆enhanced by grain boundary adjustment

Abstract

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 110 nm in width and >2 µm in length were readily obtained at temperatures as low as 950 °C, and they showed a large room-temperature tunnelling magnetoresistance (Δρ/ρ0) 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.