Colossal magnetoresistance in sol-gel derived epitaxial thin film of co-doped La1-xCaxMnOx

Electrical, magnetic, and magnetotransport properties of sol-gel derived epitaxial thin films of Co-doped La1-xCaxMnO8 are reported. The epitaxial thin films, deposited using metal-salt routed sol-gel processing, show excellent quality of epitaxy (FWHM = 0.3 degrees). Their surface roughness is about 30 Angstrom and average grain size is 500 Angstrom. The thin films exhibit the typical behavior of colossal magnetoresistive oxide, manifesting paramagnetic semiconductor to ferromagnetic metal transition near magnetic transition. The doping of Co reduces electrical conductivity, Curie temperature (T-c) and saturation magnetization (M-s). However, the peak magnetoresistance ratio does not show a monotonous change with increasing Co content. These results are interpreted by spin-disorder scattering, magnetic inhomogeneity, and lattice distortion.