Effect of annealing temperature on local distortion of La0.67Ca0.33MnO3 thin films

Mn K-edge fluorescence data are presented for thin-film samples (3000 Angst rom) of colossal magnetoresistive (CMR) La0.67Ca0.33MnO3: as deposited, and post annealed at 1000 and 1200 K. The local distortion is analyzed in term s of three contributions: static, phonon, and an extra, temperature-depende nt, polaron term. The polaron distortion is very small for the as-deposited sample and increases with the annealing temperature. In contrast, the stat ic distortion in the samples decreases with the annealing temperature. Alth ough the local structure of the as-deposited sample shows very little tempe rature dependence, the change in resistivity with temperature is the larges t of these three thin-film samples. The as-deposited sample also has the hi ghest magnetoresistance, which indicates some other mechanism may also cont ribute to the transport properties of CMR samples. We also discuss the rela tionship between local distortion and the magnetization of the sample.