Measurement and Prediction of Magnetic Losses in Mn-Zn Ferrites From DC to the Megahertz Range

The magnetic energy losses and their frequency dependence in Mn-Zn ferrites have been investigated in theory and experiment. A novel theoretical approach has been developed, which is based on the concept of loss decomposition and the appraisal of the separate contributions provided by domain wall displacements and moment rotations. It is shown that the role of eddy currents in energy dissipation is a minor one and can be appreciated in the megahertz region only. The loss contribution by domain walls versus frequency is obtained from knowledge of the quasistatic energy loss, whereas the rotational real and imaginary permeabilities are derived as solutions of the Landau-Lifshitz-Gilbert equation for distributed values of the effective anisotropy field. The model successfully applies to results obtained on commercial ferrite ring samples