Influence of Al2O3 on low-temperature resistivity minima in (1 − x)La0.7Ca0.3MnO3 + xAl2O3 composites

The unusual low-temperature resistivity upturn of composites (1 − x)La0.7Ca0.3MnO3 + xAl2O3 (LCMO/Al2O3) is presented in this paper. The depth of the resistance minima was found to increase with an increased Al2O3 content. We have fitted the resistivity versus temperature data from 5 to 50 K for all samples by an expression containing three terms, namely, inelastic scattering, and electron–electron (e–e) interaction and Kondo effects. We conclude that the e–e interaction effect is the dominant mechanism of LCMO/Al2O3 composites at low-temperature.