Magnetoelectric transport and quantum interference effect in ultrathin manganite films

The magnetoelectric transport behavior with respect to the thicknesses of ultrathin La0.9Sr0.1MnO3 films is investigated in detail. The metal-insulator phase transition, which has never been observed in bulk La0.9Sr0.1MnO3, is found in ultrathin films with thicknesses larger than 6 unit cells. Low-temperature resistivity minima appeared in films with thicknesses less than 10 unit cells. This is attributed to the presence of quantum interference effects. These data suggest that the influence of the weak localization becomes much pronounced as the film thickness decreases from 16 to 8 unit cells.