Stabilization of Barkhausen noise readings by controlling a surface field waveform

Insufficient reproducibility and measured results that are difficult to interpret are the main obstacles to widespread practical implementation of the magnetic Barkhausen noise technique as a useful non-destructive tool. This work gives a clear experimental proof that precise control of the surface magnetic field stabilizes the subsurface Barkhausen noise readout with respect to the magnetizing yoke lift-off. The surface magnetic fields above the sample were measured at two different distances by Hall sensors; the real sample field was obtained by linear extrapolation of these surface field waveforms to the sample face. This extrapolated field waveform was then adjusted to the standard triangular/sinusoidal shapes with a multi-parameter digital feedback procedure. The Barkhausen noise signal was measured locally with a bobbin coil placed on the same surface area where the magnetic field was measured.