Temperature-dependent resistivity and Seebeck coefficient in epitaxial La0.5Sr0.5CoO3 thin film

Abstract

La0.5Sr0.5CoO3 (LSCO55) thin film with a thickness of 13 nm was epitaxially grown on LaAlO3 (001) substrate by pulsed laser deposition. Its structural properties as well as its temperature-dependent electronic transport properties were investigated. X-ray diffraction confirmed single-phase “cube-on-cube” epitaxy with coherent in-plane strain. The film exhibits a low resistivity of ∼270 μΩ cm at 300 K and a quadratic temperature dependence below ∼200 K, indicating metallic behavior. The Seebeck coefficient shows two sign crossovers at ∼24 and ∼175 K with T3 dependence at low temperature. These findings demonstrate robust metallic transport in LSCO55 thin film and show that the thermoelectric response is not single-carrier-like: two Seebeck sign changes and a low-temperature dependence in T3 indicate competing carrier terms and a possible phonon drag contribution, shaped by magnetic ordering/disorder.