A general frame for the displacement model of magnetization in ferromagnetics and some of its consequences

This author has shown previously that, by the proper use of the Lagrangian Function density method, a set of equations analogous to Maxwell equations for the ferromagnetic medium is obtained, involving an additional term, called "structural currents density," in the equation. Thus, the material macroscopic parameters appear to be not the constants assumed a priori (as in classical electrodynamical analyses), but can be determined for the medium considered by taking into account the structural energies involved. The solution of the problem for the case of the plane EM wave, identified with the plane individual 180° Bloch wall, leads to the new generalized equation of motion regarding both electrodynamical as well as structural and primary magnetic aspects. Certain well-accepted views are criticized here on the role of the eddy current and the viscuous damping of Bloch wall motion, especially with respect to magnetic diffusion damping. In this paper, the generalized equation of Bloch wall motion is solved for the case of irreversible displacement essential to nonlinear magnetic applications and theory. However, the applicability of the model developed is much broader, encompassing the characterization of magnetic materials under arbitrary magnetization conditions, whenever Bloch wall motion cannot be neglected.