Study of magnetic properties of Joule heated granular CoxCu100-x ribbons

Granular Co-Cu alloy ( Co10Cu90) produced by melt-spinning and subsequently annealed in vacuum by DC Joule heating at different current densities have been investigated by DC and AC susceptibility measurements. High values of the heating current density lend to promote grain growth and to favore the increase of intergrain interactions strength, determining a variety of magnetic propeties from a collective fi freezing in random directions of moments of nanosized Co particles to an inhomogeneous and pl progressive blocking of moments of particles with increasing size. Meanwhile, significant changes of the giant magnetoresistance exhibited by the system were also observed. The correlation between microstructure, magnetic properties and GMR is discussed.