Frequency dependent hysteresis loss in SiFe

We have studied the hysteresis loss associated with nonmagnetic inclusions that are large enough to support a supplementary domain structure. This tube domain structure interacts with a main domain wall by adhering to it as long as it is near enough to the inclusion. Loss is determined by the difference in stored tube energy between the first contact with the wall and the ultimate loss of contact. Experimentally, the area of contact decreases with increasing elongation of the supplementary structure; in our theory loss of contact occurs when this area goes to zero. The tube length at which the area of contact vanishes is significantly dependent upon the applied field, which itself must increase with increasing frequency as a result of the eddy currents loss associated with motion of the main domain walls. This implies that the tube will break free at differing lengths for differing frequencies. Our calculations show, for example, for one set of observed specimen parameters and a peak magnetization one-half of saturation, that the loss due to this mechanism increases by approximately a factor of 2 between zero frequency and 60 Hz.