  (withdrawn) A combined study of magnetic susceptibility and AC resistance was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.
