Electrical transport in epitaxial and polycrystalline thin LSMO films

We report studies on the electrical transport in La0.7Sr0.3MnO3 (LSMO) thin films of different quality. The temperature dependence of the resistivity (ρ-T) of high-quality LSMO films (ρ 10 mΩ cm) can be described by a polynomial approximation based on electron-magnon, electron-phonon, electron-electron and temperature-independent scatterings. On the other hand, the ρ-T dependence of polycrystalline LSMO films prepared under less than optimal conditions (ρ 1 Ω cm) can be described by a two-conductance-channel model. The first one is a spin-polarized tunneling between neighboring ferromagnetic grains with good contacts, while the other is implemented via a thermally-activated transport through an insulator (semiconductor) phase located mainly at the grain boundaries or between grains.