Magnetic and transport parameters of LSMO and YBCO/LSMO films deposited on sapphire substrates

The La0.7Sr0.3MnO3 (LSMO) layers and YBa2Cu3O7-{\delta}/La0.7Sr0.3MnO3 (YBCO/LSMO) bilayers were grown by magnetron sputtering on sapphire (Al2O3 or ALO) substrates. Temperature dependences of resistance of single LSMO films, grown on ALO substrates were typical for polycrystalline manganite materials and the resistance decreased with decrease of the temperature at medium temperatures and increased at lower and higher temperatures. Deposition of a top YBCO layer led to a drastic increase of the sample resistance. These bilayers did not demonstrate a decreasing of the resistance with decrease of temperature. Temperature dependence of the resistance of these samples was interpreted in the framework of a phenomenological model of two intergrain conduction channels. In framework of this model, parameters of the samples were determined and discussed.