Giant AC magnetoresistance and anisotropic AC magnetoresistance in granular magnetic alloys

(withdrawn)AC resistance of melt-spun granular magnetic Cu85Co15 ribbons was measured as a function of temperature in the range 5-300 K, magnetic field Hdc in the range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.