Temperature-dependent magnetotransport of Co-Ti-O nanocomposite films

摘要

We studied the temperature dependence of transport and magnetoresistance (MR) of Co-Ti-O nanocomposite film with well-controlled size distribution, composition, and microstructure. Co-Ti-O nanocomposite film with pure metallic Co particles embedded in the oxygen-deficient TiO2 matrix was fabricated by an optimized film growth condition. Our results reveal that spin-dependent tunneling conductance is the dominant conductance mechanism at low temperature, and as temperature increases spin-independent hopping through chains of localized states in the insulating barriers becomes increasingly prominent. The almost constant MR ratio above 60K and its slight enhancement at low temperature were observed. The enhanced MR at low temperature is ascribed to the onset of higher-order cotunneling in the Coulomb blockade regime, as well as the suppression of spin-independent hopping process with decreasing temperature.