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

Abstract

Nanocomposite Co-TiO2 thin films were pre- pared 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 concen- tration in the bath on the morphology, composition, mag- netic 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 investi- gated. 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 in- creases with the rising concentration of TiO2 nanoparticles in the plating bath. This complex structure favored the in- crease of the magnetoresistance. The Co-TiO2 nanocom- posite films (containing about 1.3 at.% Ti) exhibit a gi- ant magnetoresistance contribution of 47.6 %. From the magnetic measurements, we have found that the satura- tion magnetization, the magnetic susceptibility, and the ef- fective magnetic anisotropy constant decrease with the in- creasing content of TiO2 in the thin layer. The easy mag- netization axis direction changes from in-plane to almost perpendicular-to-plane, with increasing TiO2 nanoparticles content in the film. The existence of a giant magnetoresis- tance effect in Co-TiO2 is very promising for potential ap- plications in spintronics.