Influence of microstructure on permeability dispersion and power loss of NiZn ferrite

Permeability spectra of NiZn ferrite with different microstructures had been resolved into contributions of domain wall resonance and spin rotation relaxation. The fitting results of permeability dispersion revealed the relationships among domain wall resonance, spin rotation relaxation mechanisms, and microstructures. P-cv (power loss) was analyzed by dividing P-cv into P-h (hysteresis loss) and P-e+P-r (eddy current loss and residual loss) from the frequency dependence of the power loss. When excited under large flux density, sample with larger average grain size and closed pores could obtain lower P-cv. This could be attributed to the fact that closed pores were not easy to block domain wall movement and grain boundaries became the predominant domain wall pinning factor. However, for the low induction condition, sample with small grain size had better performance on P-cv due to the fact that influence of the closed pores was more significant. With increasing frequency, P-e+P-r gradually became the predominant factors in P-cv, so the sample with small grain size was more suitable for high-frequency use. (c) 2008 American Institute of Physics.