MAGNETOTRANSPORT AND MAGNETIC-PROPERTIES OF MECHANICALLY ALLOYED COXCU100-X

Co-Cu binary alloys, whose Co concentrations range from 10 to 30 at.%, are produced by mechanical alloying. The structure, magnetoresistance (MR), and magnetism have been investigated for the as-milled and anne aled alloys. After milling for 50 h, a supersaturated solid solution o f fcc-CoCu is formed at Co concentrations of 10 to 30 at.%. The CoxCu1 00-x (x = 10-30) alloys annealed at 700 degrees C for 1 h separate int o two phases of fcc-Co and fcc-Cu. The maximum MR ratio, under 15 kOe at room temperature, is 6.4% for the sample with x = 20 annealed at 45 0 degrees C for 1 h. The samples annealed at temperatures less than 45 0 degrees C exhibit high MR ratio at x = 25. The magnetism of the samp le with x = 20, which shows a maximum MR ratio, exhibits superparamagn etic behavior, but a slight ferromagnetic behavior have also been obse rved. Co-Cu alloys produced by mechanical alloying have a wide distrib ution of Co particle size with blocking temperature from low temperatu re to room temperature.