Investigation of static and dynamic magnetic properties of Joule heated granular Co10Cu90 ribbons

The magnetic properties of a granular Co-Cu alloy (Co,,Cu,,) produced by melt-spinning and annealed by Joule heating at different DC current densities have been investigated by magnetization, DC and AC susceptibility measurements. The increase of the heating current density has been found to promote grain growth and to enhance the strength of intergrain interactions, determining a change of magnetic behavior: from a collective freezing in random directions of moments of nanosized Co particles to an inhomogeneous and progressive blocking of moments of particles with increasing size. The effects of Joule heating on microstructure and magnetic properties are discussed in relation to-the giant magnetoresistance properties exhibited by the system, which confirm the development of interparticle correlations with increasing the heating current density. (C) 1999 Elsevier Science B.V. All rights reserved.