Microstructure and inter-grain magnetoresistance in Ag-doped polycrystalline La0.67Sr0.33MnO3 thin films

Ag-doped La0.67Sr0.33MnO3 thin films with various Ag concentrations were deposited on (001) LaAlO3 substrates at 400 ◦C by using a dual-beam pulsedlaser deposition system. The Ag-doped films show polycrystalline structure with epitaxial c-axis columns. These columns were composed of closely arranged polyhedra of size 10–15 nm, resulting from the enhanced stressinduced grain boundary diffusion. In the case of heavy doping, tiny separated Ag crystals were observed at grain boundaries. Due to the interaction between the two laser-induced plumes, the Ag precipitation also helped to form anomalous clusters consisting of nano-sized grains and amorphous phase. By adjusting the deposition conditions carefully, we can tailor the microstructure of the film and correspondingly alter the resistivity and the inter-grain magnetoresistance of the Ag-doped films. Theoretical simulation led to results consistent with the microstructure observations and the magnetoresistance measurements.