Transport properties of La0.6Y0.1Ca0.3MnO3 compounds with different interfaces

The electrical resistivity ρ(T), magnetoresistivity ρ(T,H), and impedance spectroscopy Z(ω,T) of polycrystalline La0.6Y0.1Ca0.3MnO3 compounds with different intergranular surfaces were investigated. The interfaces were modified through controlled addition of pores in samples prepared by the sol-gel technique. X-ray diffraction, scanning electron microscopy, and mercury porosimetry analysis showed that all specimens are single phase having similar microstructures and differing only by the volume fraction of pore. ρ(T,H) and Z(ω,T) data revealed that all samples undergo a metal-insulator transition at T∼175 K. In addition, the Z(ω,T) data indicate two well defined contributions to the electrical resistivity. The ρ(T,H) data exhibit features of colossal magnetoresistivity CMR phenomenon but were found to be independent of porosity. The combined results suggest that the CMR effect is mainly associated with percolation of metallic regions and weakly dependent on sample morphology.