Low-field tunnel-type magnetoresistance properties of polycrystalline and epitaxial La0.67Sr0.33MnO3 thin films

Abstract

The low-field tunnel-type magnetoresistance (TMR) properties of sol-gel derived polycrystalline and epitaxial La0.67Sr0.33MnO3 (LSMO) thin films were investigated. The polycrystalline thin films were fabricated on Si (100) with a thermally oxidized SiO2 layer while the epitaxial thin films were grown on LaAlO3 (001) single-crystal substrates. The epitaxial thin films displayed both typical intrinsic colossal magnetoresistance (CMR) and abnormal extrinsic tunnel-type magnetoresistance behaviors. Tunnel-type MR ratios as high as 0.4 % were observed in the polycrystalline thin films at a field of 120 Oe at room temperature (300 K) whereas the ratios were less than 0.1 % for the epitaxial films in the same field range. The low-field tunnel-type MR of polycrystalline LSMO/SiO2/Si (100) thin films originated from the behaviors of the grain-boundary properties.