Crackling noise in ferromagnetic materials: Barkhausen effect and
asymmetry in the pulse shape
Abstract Book of the XXIII IUPAP International Conference on Statistical Physics, Genova, Italy, (9-13 July 2007)Abstract
The Barkhausen effect is due to the jerky motion of domain walls in
disordered magnetic materials, and is one example of crackling noise
in condensed matter physics. The application of an external field acts
as a pressure on domain walls, but because of the presence of defects,
as inclusions and dislocations, the motion proceeds in
avalanches. These avalanches show interesting statistical properties
that encode important information on the magnetization reversal
process on a microscopic scale. A microscopic theory based on a
Langevin equation for the elastic domain walls describes with great
accuracy most experimental results. However it does not account for
the lack of symmetry in the average pulse shape. This can be explained
by taking into account the contribution from Eddy currents, which
results in a negative effective mass associated with the wall.