Enhanced magnetoresistance in Ag-doped granular La2/3Sr1/3MnO3 thin films prepared by dual-beam pulsed-laser deposition

In this article, we report our investigations on the doping effect metallic Ag on the intergrain magnetoresistance phenomenon. ${\mathrm{La}}_{\mathrm{2/3}}{\mathrm{Sr}}_{\mathrm{1/3}}{\mathrm{MnO}}_{\mathrm{3}}$ (LSMO) thin films with Ag doping were prepared on (001) ${\mathrm{LaAlO}}_{\mathrm{3}}$ at different substrate temperatures ${\mathrm{(T}}_s)$ by the dual-beam pulsed-laser deposition technique. Grown at $T_s\text{=750\hspace{0.05em}°}\mathrm{C},$ the films are perfectly epitaxial with their c axis perpendicular to the film surface. Ag dopant cannot substitute into the LSMO lattice, thus showing no obvious effect on the magnetotransport properties of the film, though it did impair the film in-plane epitaxy and improve the intergrain diffusion of the lattice atoms. However, grown at lower $T_s\text{(400\hspace{0.05em}°}\mathrm{C}\mathrm{),}$ the films are granular with c-axis texture. The Ag dopant exists at GBs and helps to increase the local Mn spin disorder at GBs and the phase interfaces, thus enhancing the eMR value by a factor of 2 compared with the undoped film. Experiment data also suggest that the transport mechanism underlying the Ag-doping enhanced eMR is spin-dependent scattering.