Complex impedance analysis of granular La2/3Sr1/3MnO3 manganite thin films

Low-field tunnel-type magnetoresistance (MR) was enhanced through annealing in the air, in contrast to the intrinsic CMR where the optimized MR is ass ociated with the annealing in O-2, and 10 times larger MR was obtained. Imp edance analysis showed that the grain boundary resistance was 2 times large r in the film annealed in the air than that in the O-2, while the grain res istance was invariant in the films. From these results, it can be concluded that the characteristics of grain boundaries play a crucial role in low-fi eld tunnel-type MR of manganite LSMO/SiO2/Si thin films. Therefore, we sugg est that the complex impedance analysis can provide us with useful informat ion about not only transport at grain boundaries, but also the separated co ntribution of grains and grain boundaries to MR. (C) 2001 Elsevier Science B.V. All rights reserved.