  (withdrawn)AC resistance of melt-spun granular magnetic Cu85Co15 ribbons was
measured as a function of temperature in the range 5-300 K, magnetic field Hdc
in the range -60 kOe to 60 kOe, and frequency in the range 1-1000 Hz. A sharp
peak of zero-field resistance, which scales with frequency, and an associated
isotropic giant AC magnetoresistance in small fields are observed around the
temperature of collective freezing of interacting magnetic moments. Anomalous
behavior of AC resistance in large fields (Hdc > 20 kOe) is observed in a much
broader temperature range. This effect is not only frequency- dependent, but
also highly sensitive to anisotropy. We call it anisotropic AC
magnetoresistance.
