High Frequency Properties of Soft Magnetic Ferroxplana Type Ferrites

Abstract

Y-type (Ba₂Zn₂Fe₁₂O₂₂; Y), M-type (BaCo_1.1Ti_1.1Fe_9.8O₁₉; M_CT) and mixture of these hexagonal ferrites (Y+xM_CT; x=0∼3) were prepared by the conventional solid-state reaction approach. Samples were made with BaCO₃, ZnO, CoO, TiO₂ and α-Fe₂O₃ as starting materials. The frequency dependence of the initial permeability of all samples was measured using an impedance analyzer (HP4291B). The initial permeability of Ba₃Zn₂Co_1.1Ti_1.1Fe_21.8O₄₁ (x=1) was 23 (at 100MHz), which is the highest value in this study and the Snoek's product of this sample has been reached to 14.7GHz. This value is twice larger than that of Zn₂Y. The detailed analysis of frequency dependent permeability curves for these samples strongly suggests that this enhancement of the Snoek's product is due to the change of magnetic anisotropy caused by the substitution of Co²⁺ and Ti⁴⁺ ions for Fe³⁺ ions.