What does a Barkhausen surface coil actually measure ?

The surface coil, which measures the magnetic flux rate from the sample surface, is the most used sensor for Magnetic Barkhausen signal measurement. However, there is little knowledge about how the magnetic flux corresponding to Barkhausen events is leaked from the sample surface and which components of the magnetic flux density contributes to the induced signal. The present work shows an effort to answer these questions by measuring the normal and tangential components of the signals induced in the surface coil and analyzing these measurements using a micro-mesoscopic model of Barkhausen effect. The results show that the presence of even a small tilt angles of the surface coil induces not only components of the applied field in the coil, as thought so far, but also induces tangential components of the Barkhausen signal. The presence of both components of the Barkhausen effect in the induced signal due to the tilt of the surface coil could be a result of the sample surface irregularities or due to the non-uniformity of the coil winding. Finally, the outcomes also reveal that magnetic flux contributing to the induced signal comes from a ring of the material surface surrounding the surface coil. These findings have important implications for Barkhausen setup and applications.