Barkhausen Effect in Nickel-Iron Films

A statistical study of Barkhausen discontinuities in nickel‐iron films has been made by observing independent hysteresis loops obtained from different areas of each film. The magnetization changes were detected by photomultiplier sensing of the light output from a standard Kerr magneto‐optical apparatus. Observations could thus be restricted to any desired region of the film by suitably varying the light spot size and location. The sequence of Barkhausen discontinuities in a given reversal is generally random and cannot be predicted by the sequence in a previous reversal. The statistical distribution of discontinuity sizes obtained from many reversals is shown to be well described by a simple model of wall moton in which the probability of a wall stopping in an interval of distance $\mathrm{dx}$ is proportional to $\mathrm{dx}$ . The applicability of this model to bulk materials is discussed.