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

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 2×10−6–760 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.