Charge transport mechanisms in sol-gel grown LaPbMnO/LaAlO manganite films.

In this communication, structural, microstructural, transport and magnetotransport properties are reported for LaPbMnO/LaAlO (LPMO/LAO) manganite films having different thicknesses. All the films were irradiated with 200 MeV Ag swift heavy ions (SHI). Films were grown using the sol-gel method by employing the acetate precursor route. Structural measurements were carried out using the X-ray diffraction (XRD) method at room temperature, while atomic force microscopy (AFM) was performed for the surface morphology. Temperature dependent resistivity under different applied magnetic fields for all the films shows metal to insulator transition at temperature T. In addition to the metal to insulator transition at T, the films also exhibit low temperature resistivity upturn behavior. Resistivity, T and upturn behavior are highly influenced by the film thickness, applied magnetic field and irradiation. To understand the nature of charge transport for the low temperature resistivity behavior and metallic and insulating (semiconducting) regions, various models and mechanisms have been verified and the most suitable mechanism has been found for each region in the resistivity curves. Magnetoresistance (MR) is affected by temperature, film thickness and irradiation. MR behavior has been understood in terms of combined and separate contributions from grains and grain boundaries in the films.