Abstract
Fe3-xO4 films prepared by ferrite plating exhibited negative magnetoresistance associated with spin-dependent intergranular transport. The Fe3-xO4 plated films were composed of Fe3O4, γ-Fe2O3, α-FeOOH, and γ-FeOOH. We investigated the relationship between the concentration of NaNO2 in the oxidizing solution and annealing, and the degree of oxidation, magnetic properties, and current-in-plane (CIP) electrical properties. Resistivity was about 0.3-500 μcm, which is higher than that of bulk magnetite (10-2 μcm). MR ratios taken in the maximum field of 2.5 kOe increased as much as 5.7% with increasing concentrations of NaNO2. Mössbauer spectroscopy and electrical evaluation showed that an increase in Fe3+ ion content, in other words, an increase in insulating region, raised the resistivity and the MR ratio with increasing concentrations of NaNO2. The temperature dependence of the resistivity suggested that the magnetoresistance is caused by spin-dependent tunneling through the insulating region that existed in the grain boundaries.
