Giant Magnetoresistance Effect in Melt Spun CoCu granular Alloys

granular magnetic Co_xCu_1-x(x= 0.05 - 0.5) alloy ribbons were prepared by melt spinning method, and the structural, magnetotransport, magnetic properties and the effects of annealing on these properties were studied by x-ray diffraction, vibrating sample magnetometer, magnetoresistance measurement at room temperature. Giant magnetoresistance was observed over a broad range of Co concentrations with a maximum magnetoresistance (MR) ratio of 7.8% (at x = 0.20 and 500°C annealing) under a magnetic field of 20kOe. The MR ratio increases with the annealing temperature and reaches a maximum at about 500°C and then drops. The dependence of MR and magnetization on magnetic field for various granule parameters were studied by controlling the nucleation and growth of Co granules.