Thickness and microstructure dependent transport and MR in La0.7Pb0.3MnO3 manganite films

Thickness dependent modifications in the structure and microstructure and their effect on the transport and magnetotransport in chemical solution deposition (CSD) grown La_0.7Pb_0.3MnO₃ (LPMO) manganite thin films grown on single crystalline LaAlO₃ (LAO) (1 0 0) substrates have been studied. X-ray diffraction (XRD) measurements show the reduction in the microstrain at the film-substrate interface with increasing thickness. Increase in grain size and island like grain growth with the reduction in surface roughness as a function of film thickness has been observed from the microstructural studies using atomic force microscopy (AFM) and lateral force microscopy (LFM) measurements. Improvement in the surface to volume ratio (D⁻¹) resulting in the modifications in transport and magnetotransport properties of the LPMO films has been discussed in detail in the light of thickness dependent microstructural effects on the resistivity and magnetoresistance (MR) behavior. The variations in intrinsic and extrinsic MR with D⁻¹ show an interesting interplay between them, which can be explained on the basis of thickness dependent grain size, grain boundary density and grain boundary nature.