Equal permeability and permittivity in a low temperature co-fired In-doped Mg-Cd ferrite

A low-temperature co-fired In3+ ion doped Mg-Cd ferrite (Mg0.8Cd0.2Fe2−xInxO4 with 0 ≤ x ≤ 0.15) with a 3 wt% Bi2O3 additive was synthesized using a solid-state reaction method. X-ray diffraction reveals that the samples contain both a spinel ferrite phase and a CdIn2O4 dielectric phase. Following In3+ ion doping, the saturation magnetization increases first but then decreases. Coercivity, on the other hand, decreases first before it increases. The combined effects of In doping together with the addition of Bi2O3 endowed the compound materials with excellent magnetic permeability and dielectric permittivity. Using 3 wt% Bi2O3, the magnetic permeability increases first from 16 to 26.5, and then decreases to 15.6, while the dielectric permittivity increases from 19 to 32. The equivalent permeability and permittivity appears when x = 0.10. The real parts of both permeability and permittivity are about 26, and the material had low loss-tangents (both magnetic and dielectric). This indicates that this ferrite is an excellent material to be used in miniature antennas.