Effects of Substitution of Rare-Earth Metal Ions on the High-Frequency Characteristics of Co₂Z Ferrite

Abstract

Ba₃Co₂R_xFe_24-xO₄₁ (R: rare-earth element, x = 0−0.5) samples with Z-type structure were prepared by the conventional ceramic method. A series of Ba₃Co₂R_xFe_24-xO₄₁ samples (R = La, Nd, Gd, Dy, Ho, Yb) were made. The frequency dependence of the initial permeability of all samples was measured in frequency range of 0.01−1.8 GHz. The initial permeability (at 0.1 GHz) of Ba₃Co₂R_0.1Fe_23.9O₄₁ (x = 0.1, R = Gd, Dy, Ho, Yb) samples was higher than of the Co₂Z ferrite without substitution. In particular, the initial permeability of Gd³⁺-substituted Z-type ferrite sample (x = 0.1) was the highest of all samples. The crystal structure of Ba₃Co₂R_xFe_24-xO₄₁ (x = 0.1) was a single phase of the Z-type structure. As a result, rare-earth ions formed a solid solution of Co₂Z ferrite. The measured lattice constant of these samples (x = 0, 0.1) indicates that La ions substituted for Ba ions and Gd, Dy, Ho, and Yb ions substituted for Fe ions. The apparent specific anisotropy field H_A of a Gd³⁺-substituted Z-type ferrite sample (x = 0.1) was the lowest of the Ba₃Co₂R_xFe_24-xO₄₁ samples (x= 0, 0.1). It would therefore appear that the magnetic anisotropy was changed by substitution between Gd ions and Fe ions in Co₂Z ferrites. But verification by other determination is necessary.