LANGEVIN APPROACH TO HYSTERESIS AND BARKHAUSEN JUMP MODELING IN STEEL

To represent the multiplicity of metastable states in a bulk ferromagn etic material with domain-wall pinning effects, fluctuations in the do main-wall energies are described in terms of an ensemble of stochastic Langevin functions. The model parameters used are a correlation lengt h, a rms value for the amplitude of the fluctuations in the domain-wal l energy gradient, and a ''demagnetizing factor.'' The model generates both hysteresis loops and Barkhausen effect (BE) jump size distributi ons. Jump size distributions were determined experimentally for low-ca rbon rolled sheet steel with the field applied both parallel and perpe ndicular to the rolling direction. Both the model and the experimental BE jump size distributions show a power-law behavior for small jumps and a rapid cutoff at large jump sizes.