Magnetic properties and giant magnetoresistance in melt-spun Co ₁₅Cu₈₅ alloys

The structure, magnetic properties and giant magnetoresistance (GMR) of a metallic granular Co₁₅Cu₈₅ alloy have been investigated using an X-ray diffractometer and a SQUID magnetometer. The granular samples were fabricated by melt spinning and subsequently thermal annealing. Structural characterization confirmed that the samples consist of ultrafine Co magnetic particles embedded in the non-magnetic Cu matrix. Above the blocking temperature T_B, the magnetic behaviour of Co particles can be understood on the basis of paramagnetic theory. The largest change in magnetoresistance of 43.0% was observed for the as-quenched ribbon annealed at 450 degrees C. It was confirmed that the GMR is closely correlated with the Co particle size and density, which can be optimized by controlling the annealing conditions.