Abstract: CoxCu1－x granular films were prepared by electrodeposition at room temperature on semiconductor Si substrate. XRD result revealed that the as-deposited films formed a single phase metastable fcc alloy structure. Pure Co fcc diffraction peaks were observed in XRD pattern of the annealed sample, indicating phase separation occurred upon annealing. TEM characterization also confirmed the precipitation of the magnetic Co particles from the Cu-rich matrix. The giant magnetoresistance(GMR) of the films was improved after annealing. The maximum MR ratio of 8.21% was obtained for Co0.20Cu0.80 thin film after annealing at 450 ℃ for 1 h. Hysteresis loops of the as-deposited and annealed samples indicated the change from superparamagnetic to ferromagnetic contribution to the GMR effect. The values of coercivity(Hc), remanent magnetization(Mr), saturation magnetization(Ms) increased with annealing temperature. The effect of supperparamagnetic particles resulted the difference between GMR－H and M－H curves.

Key words: Granular film, Electrodeposition, Phase separation, GMR, Superparamagnetic