Effect of disorder on transport and electronic structure in LaCo1−xNixO3 system

We have systematically investigated magnetization, resistivity, thermopower and X-ray photoemission spectra(XPS) in LaCo1−xNixO3 (0∼x∼0.50∼x∼0.5) system. It is found that the transport mechanism is variable range hopping(VRH) for x≤0.1x≤0.1, and thermally activated hopping for 0.2≤x≤0.40.2≤x≤0.4. While the transport mechanism is far from the hopping process for x≥0.4x≥0.4, invalidity of the hopping process for x=0.4x=0.4 and metallic behaviour for x=0.5x=0.5, indicates that the MIT is around x=0.4x=0.4. For samples (x≥0.2x≥0.2), the thermopower can be explained well by Cutler–Mott formula which is suitable for metal with strong disorder. The metal-insulator transition in this system is a Mott–Anderson transition in which disorder effects dominates the MIT, in the presence of electron-electron correlations. The results indicate a two-band behaviour in LaCo1−xNixO3. We propose possible evolution of electronic structure to explain these phenomena.