Abstract
Surface morphology, microstructure, magnetic and transport properties of nonuniform Co0.53Ti0.47Oδ nanocomposite films fabricated by reactive cosputtering have been investigated. We change the oxygen partial pressure (PO) to modulate the oxygen concentration in the films. The average surface roughness first decreases, and then increases with the increase of PO. The films are composed of Co0, Co2+, Ti3+, Ti4+ and O2− ions, and small metal Co grains appear. The saturation magnetization of the films decreases with the increase of PO, which can be ascribed to the antiferromagnetic superexchange interaction between Co2+–O2−Co2+ since the number of Co2+–O2−Co2+ may increase with the increased PO. The resistivity of the samples decreases with the increase of temperature, showing a semiconducting mechanism. The room-temperature resistivity increases with PO, following a relation of logρ=AlogPO. Magnetoresistance (MR) of the films saturated at a field of 10kOe, and varies with the measuring temperature with a relation of logMR=ClogT, where at PO<2.5% MR increases, but at PO⩾2.5% MR decreases with the increase of temperature.
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