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 /spl Delta/M follows a power law probability distribution: P(/spl Delta/M)=/spl Delta/M/sup -/spl alpha//. The critical exponent /spl alpha/ 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 /spl mu/m 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.