부산대학교 도서관

Annealing dependence of the lattice parameter, resistivity, magnetoresistance and thermopower have been studied on Nd.sub.0.[7-Sr.sub.0.33]MnO.sub.3 thin films deposited on LaAlO.sub.3 and alumina substrates by pulsed laser ablation. Upon annealing at 800degC and 1000degC the lattice constant of the LaAlO.sub.3 film tends toward that of the bulk target due to reduction in oxygen vacancies. This results in a metal-insulator transition at temperatures which increase with progressive annealing along with a decrease in the observed low temperature MR. Using a magnon scattering model we estimate the e .sub.g bandwidth of the film annealed at 1000degC and show that the magnon contribution to the resistivity is suppressed in a highly oxygen deficient film and gains prominence only upon subsequent annealing. We also show that upon annealing, the polaron concentration and the spin cluster size increases in the paramagnetic phase, using an adiabatic polaron hopping model which takes into account an exchange dependent activation energy above the resistivity peak.