Compositional dependence of the electromagnetic wave absorption properties of BaFe_12-x-yTi_xMn_yO₁₉ in the GHz frequency range

The compositional dependence of the electromagnetic wave absorption properties of Barium M-type ferrite, in which a mixture of Ti and Mn were substituted for Fe, was investigated. Single phase M-type structure was obtained for the BaFe_12-x-yTi_xMn_yO₁₉ sintered samples with compositions x<2.5 and y<2.5, and Mn substitution allowed the single phase to form at higher Ti contents. It was found that the natural resonance frequencies (f_r) of these sintered samples can be controlled in the range 3.85 to 60.18 GHz, by changing the Ti and Mn content. Almost all of the samples in the M-type single phase region impedance-matched and exhibited a minimum reflection loss (R.L.) less than -20 dB at matching frequencies (f_m), with matching thicknesses (d_m) smaller than 4 mm, which demonstrates that these ferrites can function as thin electromagnetic wave absorbers in this frequency range. Some samples outside this single phase region with a high Mn and Ti content also impedance-matched, however the impedance matching is more sensitive to changes in Ti content than in Mn content. As a result, f_m, and d_m values varied from 33.25 to 3.75 GHz and from 0.27 to 3.80 mm, respectively.