Novel Method for Evaluating Frequency Response of Permeabilities in the c-Plane and Along the c-Axis of Z-Type Hexagonal Ferrite

In this study, a novel method was developed to evaluate the permeability along a certain direction (directional permeability) in the high-frequency range. Two kinds of polycrystalline textured Z-type hexagonal ferrites whose easy planes of magnetization lie in a certain plane and in a certain direction were prepared by molding under a magnetic field; these ferrites were used in this method. The permeabilities that were measured from three toroids cut from these textured ferrites were converted to directional permeabilities by examining the relationship between the permeability measured from the toroid and directional permeability. It was noted that the highest directional permeability of over 50 was obtained along the c-plane below 300 MHz, whereas negative permeability values were observed from 1.2 to 10 GHz. On the other hand, the lowest directional permeability of 4 was obtained along the direction that is normal to the c-plane. These results can be made use of designing various inductive devices.