Matching Permeability and Permittivity of Ga-Substituting Mg-Cd Ferrites for High-Frequency Antennas

This work mainly investigated the effects of gallium-substituting iron on the magnetic and dielectric properties of Mg-Cd ferrites Mg_0.8Cd_0.2Fe_2-xGa_xO₄ (x = 0.0, 0.05, 0.10, and 0.15) for high-frequency antennas. All the samples were synthesized at 1170 °C. XRD patterns indicated the samples crystallized in normal spinel structure. Magnetic and dielectric spectrum measurement results revealed that the permeability and permittivity of the samples were tailored with change of x value. Finally, the composites possessed excellent matching permeability (μ′) and permittivity (ε′) (x = 0.10, μ′/ε′ ≈ 1.2), over a long frequency range from 1 to 40 MHz. Comparatively, low dielectric loss tanδ_ε and magnetic loss tanδ_μ (tanδ_ε ≈ 0.003, tanδ_μ ≈ 0.035) were obtained due to densification sintering displayed in the SEM figures. Furthermore, magnetic properties were enhanced, such as increased saturation magnetization (approximately 22.14 emu/g) and decreased coercivity (approximately 51.67 Oe), as x value increased. These properties validated the introduction of Ga ions could take effect in high-frequency region applications for Mg-Cd ferrites.