Magnetomechanical Damping at Low Temperatures

Magnetomechanical damping (MMD) at low temperatures shows marked departures from the well-established phenomenological description of MMD at room temperature. There is enhanced damping (the Bruner-Heller rise) at low amplitudes generally said to have a magnetic origin, be hysteretic, and sometimes amplitude-dependent, but the falloff in the transition to higher temperatures is frequency-dependent. A recent mode1 considers that the Rayleigh MMD at room temperature arises from successive cooperative shifts (self-similar transformations) of the whole domain structure at once. It appears that the Bruner-Heller rise in pure iron may well be a manifestation of the localized hysteretic bowing motion of domain walls, the equivalent of the Granato-Lücke damping for dislocations. For alloys, the data are supportive but incomplete