Observation of Barkhausen noise in a 20×20 μm permalloy thin film square dot

Barkhausen jumps in the magnetic hysteresis loop of a single permalloy thin film square dot of 20×20 μm in size and 80 nm thick have been observed, for the first time, with a magneto-optical ellipsometer which is capable of recording a complete loop in seconds and in a single sweep of applied field. About 6000 loops have been measured and separately recorded: each loop is different from the others. The statistical properties of the Barkhausen jumps are presented and discussed