Giant magnetoresistance in Co-Cu-Ni granular ribbons

We have systematically investigated the structural, magnetic and transport properties of as-quenched and annealed Co20NixCu80-x (0 less than or equal to x less than or equal to 20) granular alloys prepared by melt spinning. T he microstructure of granular ribbons of Co-Ni-Cu shows a matrix in which n anoparticles of Co-Ni are well distributed, very different from that of gra nular ribbons of Ca-Cu in which fun-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 magnet oresistance (Delta R/R congruent to 6.2% at 300 K for Co20Ni5Cu75, which is larger than in as-quenched and annealed Co-Cu ribbons.