We have systematically investigated the structural, magnetic and transport properties of as-quenched and annealed Co20 Nix Cu80-x (0 x 20) granular alloys prepared by melt spinning. The microstructure of granular ribbons of Co-Ni-Cu shows a matrix in which nanoparticles of Co-Ni are well distributed, very different from that of granular ribbons of Co-Cu in which full-grown Co microparticles are embedded in a Cu matrix. The phase segregation in the Co-Ni-Cu granular ribbons is not a pure nucleation and growth process as in the Co-Cu granular ribbons, but also not purely due to spinodal decomposition. In contrast to the ribbons with high Ni content, the low-Ni-content ribbons show an increase in magnetoresistance ( R /R 6.2% at 300 K for Co20 Ni5 Cu75 , which is larger than in as-quenched and annealed Co-Cu ribbons.

The structure and magnetoresistance of as-quenched and annealed Co 15−x Fe x Cu 85 (x = 0, 3, 6, 9, 12, 15) granular alloys have been investigated. Co-Fe-Cu nanoparticles with sizes in the range of 2-3 nm, 10-20 nm and ∼100 nm are embedded in a Cu matrix in Co-Fe-Cu granular ribbons. The giant magnetoresistance of the granular alloys decreases with increasing Fe content. The Co-Fe-Cu nanoparticles with large size result in a decrease of the number of nanoparticles, the interfaces for spin-dependent scattering of electrons and thus the magnetoresistance.

Effects of B addition on the structure and magnetoresistance of as-quenched and annealed Co-Cu granular alloys have been studied. The formation of the Co2B phase reduces the number of small magnetic particles, which are the centres for spin-dependent scattering. The magnetoresistance of Co-Cu-B granular ribbons decreases with increasing B content.