Bias dependent intergrain tunneling in lanthanum manganite thin films

Bias dependent magnetoresistance of morphologically different La _1-xSr_xMnO₃ (LSMO) films, i.e., epitaxial and polycrystalline films, are investigated. I-V curves exhibit nonlinear behavior indicative of electron tunneling between neighboring grains. Furthermore, two clear minima are observed in the bias dependent magnetoresistance of the polycrystalline film on sapphire substrate in spite of no anomalous behavior in the epitaxial film. The minima appear at the voltages where the I-V curve deviates from the ohmic character. The bias dependent magnetoresistance increases with increasing voltage. The novel aspects of the bias dependent magnetoresistance are discussed in connection with spin polarized tunneling