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

Nanocomposite Co-TiO2 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-TiO2 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-TiO2 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-TiO2 is very promising for potential applications in spintronics.