DYNAMICS OF A FERROMAGNETIC DOMAIN-WALL AND THE BARKHAUSEN EFFECT

We derive an equation of motion for the dynamics of a ferromagnetic do main wall driven by an external magnetic field through a disordered me dium, and we study the associated depinning transition. The long-range dipolar interactions set the upper critical dimension to be d(c) = 3, so we suggest that mean-field exponents describe the Barkhausen effec t for three-dimensional soft ferromagnetic materials. We analyze the s caling of the Barkhausen jumps as a function of the field driving rate and the intensity of the demagnetizing field, and find results in qua ntitative agreement with experiments on crystalline and amorphous soft ferromagnetic alloys.