Magnetic properties and giant magnetoresistance in melt-spun Co-Cu alloys

Magnetic, structural, and transport properties of as-quenched and annealed Co₁₀Cu₉₀ samples have been investigated using x-ray diffraction and a SQUID magnetometer. The largest value of MR change was observed for the as-quenched sample annealed at 450°C for 30 min. The magnetic and transport properties closely correlate with the microstructure, mainly with Co magnetic particle size and its distribution. For thermal annealing the as-quenched samples below 600°C, the Co particle diameters increase from 4.0 to 6.0 nm with a magnetoresistance (MR) drop from 33.0% to 5.0% at 10 K. Comparison with the theory indicates that the interfacial electron spin-dependent scattering mechanism correlates with GMR for Co particle diameters up to about 6.0 nm.