The Effects of Heat Treatment on the Electronic Transport of La1.4Sr1.6Mn2O7+δ and La0.67Ca0.33MnO3+δ

C.-J. Liu；M.-S. Huang；C.-S. Sheu

Chinese Journal of Physics

38卷2S期（2000 / 04 / 01）

360 - 365

英文

We report measurements of thermopower and resistivity for La1.4Sr1.6Mn2O7+δ and La0.67Ca0.33MnO3+δ ceramics treated in different temperatures and atmosphere. Chemical titration is used to determine both of the average valence of manganese and content of oxygen. As the samples are annealed at lower temperatures, the resistivities of both La1.4Sr1.6Mn2O7+δ and La0.67Ca0.33MnO3+δ reduce in magnitude. The effect of nitrogen-annealing leads to a reduction of the resistivity for La1.4Sr1.6Mn2O7+δ but an increase for La0.67Ca0.33MnO3+δ. Thermopower data suggest more than one type of carrier existing in the system. Transport data seem to support the polaron hopping in the high temperature regime.