The grain size dependence of the resistance behaviors in doped lanthanum manganite polycrystalline films

Using the sol-gel spin-coating method, La0.67Sr0.33MnO3 and La0.7Ca0.3MnO3 polycrystalline films have been prepared. The polycrystalline films show mu ch lower resistivity peak temperature T-p than that of the corresponding ep itaxial film, and T-p shifts to higher temperature when the annealing tempe rature increases. The magnetization measurement reveals that all of the pol ycrystalline films have the same magnetic transition temperature as the cor responding epitaxial films. These results are different from the previous w orks. We ascribe the difference to the grain size of our polycrystalline sa mples being much smaller, so the conduction through the grain boundaries pr edominates over the intragrain conduction. In this case, spin disorder and magnetocrystalline anisotropy should be taken into account in explaining th e magnetotransport behavior. (C) 2000 American Institute of Physics. [S0021 -8979(00)06004-7].