ANALYSIS OF EDDY-CURRENT LOSS IN MN-ZN FERRITES FOR POWER-SUPPLIES

From the investigation regarding the dependence of power loss and elec trical resistivity at a temperature at which crystalline anisotropic e nergy becomes zero, eddy current loss and residual loss could be obtai ned separately. The increase in residual loss as exciting magnetic flu x density, B-m, follows B-m(2) at 1 MHz and B-m(3-4) at 100 kHz. This result shows that the residual loss arises from spin rotation inside t he magnetic domain wall. The domain size was estimated to be in the re gion of 1-2 mu m by applying the barlike domain-wall model to the eddy current loss obtained experimentally. The frequency of the spin rotat ion is estimated using the domain size, the thickness of the domain wa ll, and the exciting condition. The spin rotation inside the domain wa ll can reach the magnetic resonant frequency of Mn-Zn ferrites under t he exciting condition of f > 500 kHz and B-m > 70 mT. This magnetic re sonance occurring inside the domain wall is considered to generate the large residual loss. (C) 1997 American Institute of Physics.