Dipolar interactions in ferromagnetic systems: Dynamic hysteresis from parallel domain walls

We present a model for the study of the hysteretic behavior of a disordered ferromagnetic system with an array of parallel Bloch domain walls. We write the equations of motion of the walls under an external magnetic field driving, considering long-range dipolar interactions and disorder. We calculate analytically an expression for the magnetic susceptivity Z, and find a logarithmic dependence for Z on the number of domains. We study the dynamic hysteresis, which behavior could be explained by the theory of loss separation. (c) 2007 Published by Elsevier B.V.