Electromagnetic and microwave absorption properties of BaMg_xCo_1−xTiFe₁₀O₁₉

To improve the impedance matching and then achieve a better microwave absorption performance in electromagnetic absorber, the Mg²⁺ was added to occupy the sites of Co²⁺ in hexagonal-type ferrite BaCoTiFe₁₀O₁₉. BaMg_xCo_1−xTiFe₁₀O₁₉ were synthesized by a simple sol-gel combustion technique and the phase of BaMg_xCo_1−xTiFe₁₀O₁₉ was confirmed by X-ray diffraction analysis (XRD). The grain size of BaMg_xCo_1−xTiFe₁₀O₁₉ was in the range of 100–400 nm and crystal particles were refined with the augment of doped Mg²⁺. Based on the static magnetic measurement, the coercivity (H_c) increased and the saturation magnetization (M_s) decreased as the x increased. Moreover, it was found that BaMg_0.4Co_0.6TiFe₁₀O₁₉ possessed a maximum reflection loss of −33.7 dB with a matching thickness of 2.0 mm measured by the vector net-analyzer in the frequency of 0.5–18 GHz, which also had a bandwidth below −20 dB ranging from 11.5 GHz to 17.2 GHz. Meanwhile, the permeability of the prepared ferrites could be adjusted and a proper match was provided between dielectric and magnetic properties by controlling the doped content of Mg²⁺, which would be significant to the application of BaMg_xCo_1−xTiFe₁₀O₁₉ in the field of the microwave absorbing materials. - Highlights: • The Mg²⁺ ions were first employed to occupy the place of Co²⁺ ions in BaCoTiFe₁₀O₁₉. • The grains were refined as Co substitution by Mg in ferrite. • The peaks of complex permeability shift to high frequency with Mg²⁺ substituted. • The coercivity increased and saturation magnetization slightly decreased. • Substitution of Mg²⁺ enhanced microwave absorption and broadened bandwidth.