Investigation of Structural, Magnetic and Magnetotransport Properties of Electrodeposited Co–TiO2 Nanocomposite Films

Nanocomposite Co?CTiO₂ thin films were prepared by simultaneous electrodeposition of Co and TiO₂ on a Cu substrate from a solution based on Co sulfate in which TiO₂ nanoparticles were suspended by stirring. We investigated the influence of the TiO₂ nanoparticles concentration in the bath on the morphology, composition, magnetic and magnetotransport properties of the films. The Co?CTiO₂ thin films were characterized by using scanning electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction analyses, and their magnetic properties were evaluated by using an induction type device with data acquisition system and a torque magnetometer. The current in-plane transport properties of the films have been investigated. The results showed that the films were composed of a Co metal matrix containing embedded TiO₂ nanoparticles and cobalt hydroxide which is formed simultaneously with cobalt metal deposition. The amount of TiO₂ in the film increases with the rising concentration of TiO₂ nanoparticles in the plating bath. This complex structure favored the increase of the magnetoresistance. The Co?CTiO₂ nanocomposite films (containing about 1.3 at.% Ti) exhibit a giant magnetoresistance contribution of 47.6 %. From the magnetic measurements, we have found that the saturation magnetization, the magnetic susceptibility, and the effective magnetic anisotropy constant decrease with the increasing content of TiO₂ in the thin layer. The easy magnetization axis direction changes from in-plane to almost perpendicular-to-plane, with increasing TiO₂ nanoparticles content in the film. The existence of a giant magnetoresistance effect in Co?CTiO₂ is very promising for potential applications in spintronics.