Correlations of triggering noise in driven magnetic clusters

We show that the temporal fluctuations Delta H(t) of the threshold driving field H(t), which triggers an avalanche in slowly driven disordered ferroma gnets with many domains, exhibit long-range correlations in space and time. The probability distribution of the distance between successive avalanches as well as the distribution of trapping times of domain wall at a given po int in space have fractal properties with the universal scaling exponents. We show how these correlations are related to the scaling behavior of Barkh ausen avalanches occurring by magnetization reversal. We also suggest a tra nsport equation which takes into account the observed noise correlations. ( C) 2000 Elsevier Science B.V. All rights reserved.