Giant magnetoresistance in melt-spun Cu/sub 80/Ni/sub 16/Fe/sub 4/ ribbons

We present the magnetoresistance and magnetization behavior in melt-spun Cu/sub 80/Ni/sub 16/Fe/sub 4/ ribbons. The as-spun ribbon exhibits magnetoresistance (MR) ratios of 13% and 0.1% at 5 K and room temperature, respectively. The MR behavior of the ribbon is found to be mostly related to the magnetic fluctuation scattering at temperatures well above the blocking temperature and the spin-dependent scattering at lower temperatures. The latter mechanism can be understood in terms of the blocking of small magnetic particles and paramagnetic-ferromagnetic transformation at lower temperatures, as supported by the magnetization data. When the microstructure is modified by proper heat treatment, the ribbon exhibits significant giant magnetoresistance behavior both at room temperature and 5 K.