Anomaly of AC resistance in magnetic nanoparticle alloys at spin-glass-like transition

(withdrawn) A combined study of magnetic susceptibility and AC resistance was performed on melt-spun Cu-Co granular magnetic ribbons. The AC resistance as a function of temperature has a sharp maximum. We associate it with a diverging correlation length at the temperature of collective freezing of magnetic moments via increasing magnetic losses in the induced non-uniform field. Application of this model to the experimental data allows a direct determination of the critical exponent of correlation length on both sides of the transition. Giant AC magnetoresistance is observed at the freezing temperature.