GIANT MAGNETORESISTANCE IN MELT SPUN CU-CO ALLOYS

Cu1-xCox alloys with x = 0.1 and x = 0.2 have been prepared by conventional melt spinning. The rapid solidification process results in an extended solubility of Co in Cu although some Co precipitates already during quenching. In the as-quenched ribbons, the magnetoresistance (MR) is only of the order of 1.5%. It increases dramatically with the controlled nucleation and growth of Co precipitates from the supersaturated Cu matrix. The highest MR of 11% at 300 K occurs for Cu90Co10 after an aging at about 440-degrees-C when the Co clusters are superparamagnetic. Saturation is possible only after a higher annealing or at lower measuring temperatures. For the optimally annealed samples the MR increases to 36% at 30 K.