Direct Observation of Large Barkhausen Jump in Thin Vicalloy Wires

Thin Vicalloy wires with bistable magnetization states exhibit a fast magnetization reversal when excited by an external magnetic field. The reversal is accompanied by a large Barkhausen jump that is independent on the rate of change of the external field. For indirect observation of the large Barkhausen jump and for many sensor applications, a pickup coil is used in general. The amplitude of the voltage induced in the pickup coil is independent of the change rate of the magnetic field. For direct observation of the magnetization reversal, a magnetic field camera based on the Faraday effect is used to measure the radial magnetic field of the wire. Excitation of the Barkhausen jump is done by a rotating magnet. The radial magnetic structure clearly shows the magnetization reversal of the large Barkhausen jump for very small changes in the magnetization field.