GIANT MAGNETORESISTANCE IN MELT SPUN CU-CO ALLOYS

Cu1-xCox alloys with x = 0.1 and x = 0.2 have been prepared by convent ional melt spinning. The rapid solidification process results in an ex tended solubility of Co in Cu although some Co precipitates already du ring quenching. In the as-quenched ribbons, the magnetoresistance (MR) is only of the order of 1.5%. It increases dramatically with the cont rolled nucleation and growth of Co precipitates from the supersaturate d 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 superparamagn etic. Saturation is possible only after a higher annealing or at lower measuring temperatures. For the optimally annealed samples the MR inc reases to 36% at 30 K.