On the HF permeability of dense ferrites in polarizing fields

Investigation of the HF permeability of toroidal-shaped ferrite samples in a perpendicular dc field. Dense polycrystalline Ni-Zn and Li-Zn samples have been measured in the 200-600 MHz range, as well as a rather perfect YIG single crystal. Measurements were taken in a coaxial resonator. The samples were sandwiched between Armco iron pole pieces. The permeability appeared to be inversely proportional to the dc field. At 200 MHz a permeability of 30 with could be obtained, as well as a permeability of 40 with . At 600 MHz the permeability for was 18. The results found with the single crystal could be understood in some detail from the magnetization and anisotropy data. The remaining loss factor is assumed to be due to persisting domains.