Permeability mechanisms in high frequency polycrystalline ferrites

The initial complex permeability has been measured versus frequency for various soft polycrystalline ferrites under special biasing conditions. According to the ferrite microstructure and to the static biasing, the field orientation and magnetization mechanisms such as spin rotation or domain wall motion have a more or less important contribution. Even for low anisotropy ferrites, small grain size improves the high frequency properties by enhancing the spin rotation contribution to the detriment of the domain wall motion.