Influence of oxygen vacancies on transport properties of La2/3Ca1/3MnO3-y films grown on SrTiO3 substrates

We prepared La2/3Ca1/3MnO3-y films with various oxygen contents on SrTiO3 substrates and measured the temperature-dependent resistivity of the manganite films under tensile stress due to the lattice mismatch between manganites and single-crystal substrates. The effect of oxygen vacancies on the transport properties of the films was investigated. The experimental results reveal that the dependence of temperature on the resistivity of fully oxygenated films can be attributed to the adiabatic small-polaron conduction and unconventional one-magnon scattering at temperatures above and far below the insulator-metal (I-M) transition temperature, respectively. However, for highly oxygen -deficient films, the temperature-dependent resistivity can be ascribed to Mott's variable-range-hopping and small polaron metallic conduction at temperatures above and far below the I-M transition temperature, respectively.