Barkhausen jumps in a magnetic microstructure

The magnetization process in a square dot of permalloy having a size of 20 mu m and 80 nm thickness has been investigated with a focused magneto-optic al hysteresigraph. With this apparatus, it is possible to measure in a few seconds the hysteresis loop with a signal-to-noise ratio adequate for the o bservation of Barkhausen jumps also in such a small magnetic sample. From a sequence of 6000 loops, systematic data on the statistical properties of t hese jumps have been extracted. The observed behavior shows strong deviatio ns with respect to the available data on bulk samples and thin films. (C) 2 000 American Institute of Physics. [S0003-6951(00)03017-5].