A numerical model for Barkhausen coercivity

The well-known Barkhausen effect occurs when a domain wall moving through a crystal gets pinned at imperfections. A numerical model is described here that gives a possible mechanism for this effect. It is assumed that the imperfection is a spherical nonmagnetic ’’hole’’ in an otherwise perfect ferromagnetic material which generally repels the approaching wall. The equilibrium wall shapes, as the applied field is slowly increased, are successively computed. When either the wall ’’touches’’ the hole, causing a reduction in the induced pole strength, or the wall closes about the hole, a sudden irreversible change is triggered. The field strength at which this takes place is the coercive force.