Magnetoresistance of manganite thin films induced by reaction with substrate

Abstract

Enhanced low-field magnetoresistance (MR) of polycrystalline lanthanum strontium manganite thin films is demonstrated using an approach in which effective barriers are formed by the heat-treatment induced reaction with an insulating substrate. The heat treatment induces two chemically different processes in the film, i.e., grain growth and chemically reactive penetration. In the former process, the MR decreases due to reduction of the number of grain boundaries, while in the latter the penetration of an insulating substrate and reacted materials forms effective barriers for the electron tunneling between ferromagnetic grains. The formation of effective barriers causes a factor of 3 larger MR than as-prepared films. These results suggest that the MR can be prospectively controlled in this fashion. © 2001 American Institute of Physics.