Effects of oxygen content on the transport property of La0.7Ce0.3MnO3+δ film

Effects of oxygen content on the transport property of the La0.7Ce0.3MnO3+δ film, which was believed an electron-doped manganite, have been experimentally studied. The content of oxygen of the film was modified by repeatedly annealing the film in vacuum at various temperatures between 200 and 550 deg. C, and the resistivity was measured as a function of temperature after each annealing. The film was hole-doped when it was oxygen rich, and a metal-to-semiconductor transition (MST) was found. With the decrease of the oxygen content, the MST temperature decreased, and finally the MST vanished, and the resistivity increased overall. The sample showed semiconductive behaviors, when it was true electron-doped (average valence of Mn less than 3+). The results imply that the magnetic and transport behaviors and strong magnetic-resistive correlation in La0.7Ce0.3MnO3+δ film result from the interaction between Mn3+ and Mn4+