Magnetic Noise in Structured Hard Magnets

The anomalous Hall effect of wires patterned from (Co{90}Fe{10}/Pt){n} multilayers, with 10<or=n<or=50, is used to determine the magnetization process in a small volume of maze domains. Time-independent 1/f noise appears in samples with a quality factor Q<1 at points on the hysteresis loop where the magnetization reverses continuously. The magnetic noise is associated with reversible excursions of segments of a domain wall approximately 100 nm long. Barkhausen jumps are observed close to either the switching field or the saturation field where the noise power spectrum varies as 1/f{1.7}, and its magnitude decays with time.