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

A comparative study of the effect of annealing in reduced oxygen pressure o n the electrical transport properties of (La1-xNdx)(0.7)Sr0.3MnO3 (x = 0, 0 .25, 0.5, 0.75, and 1) epitaxial thin films and bulk materials has been car ried out. The epitaxial films grown by pulsed laser ablation were in situ a nnealed in an oxygen atmosphere of 2 x 10(-6)-760 Torr at 700 degrees C for 1 h. It is found that the electrical transport behavior of the epitaxial f ilm is insensitive to the annealing pressure. A similar thermal treatment o n the bulk materials at 5 mTorr oxygen ambient, however, caused a dramatic change in their resistivity-temperature dependence. Our results suggest tha t the annealing has a prominent effect on the properties of grain boundary, which plays an important role in determining the electrical transport beha vior of polycrystalline manganites. (C) 2000 American Institute of Physics. [S0021-8979(00)04306-1].