Giant magnetoresistance in melt-spun granular Cu100-x Cox alloys with correlated magnetic moments

A study of giant magnetoresistance (GMR) has been performed on melt-spun ribbons of Cu100-xCox (5 less than or equal to x less than or equal to 20) subjected to DC Joule heating in order to optimise the GMR response. The GMR results, plotted as functions of the reduced magnetisation, exhibit significant deviations from the parabolic behavior predicted in the case of no correlation among magnetic moments. A simple theory of the GMR in Cu-Co granular systems, taking explicitly into account the correlation existing among the magnetic particles, is highlighted. The effect of both Co content and degree of magnetic correlation on the maximum GMR values attained for each composition is briefly discussed