Magnetoelastic Damping in Zone-Melted Iron

Ferromagnetic domain walls tend to move in phase with an alternating stress or magnetic field. This movement is opposed by directionally ordered interstitial atoms. When the time associated with the relaxation process is the order of the period of the moving walls, a phase lag between the applied field and the domain-wall movement occurs. This phase lag, coupled with normal hysteresis losses, causes a variety of magnetic and magnetoelastic phenomena, among them a strong temperature dependence of the ac magnetic permeability and a broad internal-friction peak in the temperature range of the Snoek peaks. These phenomena can be interpreted in terms of viscoelastic theory, with a relaxation process (interstitial directional ordering) having a unique activation energy.