Institute for Applied Materials – Materials Science and Engineering

Magnetic Barkhausen Noise

When an external magnetic field is applied on ferromagnetic materials the growth of magnetic domains that have a similar magnetization orientation to the applied magnetic field can be investigated. The growth occurs by shifting the so-called Bloch-walls at the expense of the unevenly oriented domains and is hindered by lattice defects. Above a certain field strength, the defects can be overcome and a sudden irreversible wall movement occurs until a new defect will blockade the movement once again. Defects are for example grain boundaries, dislocations, voids or inclusions. This effect leads to a discontinuous change in magnetization. These jumps during magnetization were discovered by Heinrich Barkhausen and are therefore also called magnetic barkhausen noise (MBN). The MBN makes it possible to perform a non-destructive sample characterization because it is dependent on both mechanical and microstructural properties. The MBN can be used to make statements about grain size, plastic deformation and residual stress state.

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