Correlation between Losses, Complex Permeability and Electron Diffusion in Power Ferrites

Abstract
The contribution of electron diffusion to power losses was studied. From the frequency dependence of complex permeability, the damping and resonance parameters were determined in the frame of the forced oscillator model. The damping constant correlates well with the difference between total and hysteresis losses. The complex permeability, the loss factor and the conductivity were measured as a function of frequency between 80 K and 300 K. From the tan δ - maximum over temperature for different frequencies an activation energy was calculated. Its value agrees with the activation energy for the conductivity, showing a clear correlation between tan δ and electron diffusion for power materials. In an attempt to influence the electron diffusion-driven magnetic behavior, electric fields perpendicular to the magnetic flux were applied to ring cores. The dependence of magnetic properties on electric fields as a function of temperature, frequency, amplitude and phase shift between magnetic and electric fields was measured. A dramatic effect on power losses in dependence of field direction was observed, showing a maximum at the temperature of the secondary permeability maximum.