Statistical fluctuations during magnetization reversal in Fe films

The statistical properties of Barkhausen noise in an epitaxial Fe film grown on MgO have been characterized with a focussed magnetooptical hysteresigraph. If the measurements are performed on a large region of the sample surface the jump amplitude ΔM follows a power law probability distribution: P(ΔM)=ΔM^-α. The critical exponent α is equal to 1.1. This value is lower than previous observations on bulk samples and polycrystalline films. The same distribution measured from a region having 50 μm size consists of a series of well separated peaks. The connection between this scale length and the continuous behavior on a larger scale is discussed