Giant magnetoresistance of melt-spun Cu-Ni-Fe alloys with spinodally-decomposed structure

We report the observation of giant magnetoresistance effect in as-spun and annealed spinodally decomposed Cu-Ni-Fe alloy ribbons. The magnetoresistance ratio of 9.5% was observed at 4.2 K for as-spun Cu/sub 70/Ni/sub 15/Fe/sub 15/ ribbon, which could be increased to 12.0% by annealing at 400 C for 15 min. In contrast to the temperature dependence of the magnetoresistance ratio of sputtered Cu-Ni-Fe films, melt-spun Cu-Ni-Fe ribbons show an increase in the magnetoresistance ratio upon cooling from room temperature to 4.2 K. The observed giant magnetoresistance behavior in Cu-Ni-Fe ribbons is mostly caused by the spin-dependent scattering at the two-phase interface and in the ferromagnetic phase, as well as scattering due to magnetic fluctuations such as very fine ferromagnetic particles.