Effect of annealing in reduced oxygen pressure on the electrical transport properties of epitaxial thin film and bulk (La₁₋ₓNdₓ)₀.₇Sr₀.₃MnO₃

Abstract

A comparative study of the effect of annealing in reduced oxygen pressure on the electrical transport properties of (La₁₋ ₓNdₓ)₀.₇Sr₀.₃MnO₃(x=0, 0.25, 0.5, 0.75, and 1) epitaxial thin films and bulk materials has been carried out. The epitaxial films grown by pulsed laser ablation were in situ annealed in an oxygen atmosphere of 2 X 10⁻ ⁶– 760 Torr at 700 °C for 1 h. It is found that the electrical transport behavior of the epitaxial film is insensitive to the annealing pressure. A similar thermal treatment on the bulk materials at 5 mTorr oxygen ambient, however, caused a dramatic change in their resistivity-temperature dependence. Our results suggest that the annealing has a prominent effect on the properties of grain boundary, which plays an important role in determining the electrical transport behavior of polycrystalline manganites.