Conductance and conduction noise of polycrystalline La0.7Ca0.2Ba0.1MnO3 films on different substrates

La0.7Ca0.2Ba0.1MnO3 (LCBMO) films were prepared by ultrasonically assisted spray pyrolysis deposition on LaAlO3 and Al2O3 single crystal substrates. Conductance-voltage (G-V) characteristics and conduction noise of the two films were found to be different. G-V characteristics of LCBMO film on LaAlO3 were linear indicating the spin dependent scattering across the grain boundaries whereas for the film on Al2O3, G-V characteristics at low temperature (T<210K) were nonlinear indicating dominant transport mechanism as spin polarized tunnelling. Normalized conduction noise of LCBMO film on LaAlO3 was one order lower to that of film on Al2O3. These differences in conductance-voltage and conduction noise characteristics of the two films are attributed to the presence of more disordered grain boundaries in LCBMO film on Al2O3 as compared to the films on LaAlO3 substrate.