Barium M-type ferrite as an electromagnetic microwave absorber in the GHz range

The electromagnetic microwave absorption properties of Barium M-type ferrite, in which Fe3+ was substituted by (Ti0.5Mn0.5)(3+), were investigated in the GHz frequency range. The anisotropy field (H-A) of Barium M-type ferrite can be changed by varying the Ti0.5Mn0.5 content, which enables the natural resonance frequency (fr) to be controlled, in the range 48 GHz to 8 GHz. BaFe12-x(Ti0.5Mn0.5)(x)O-19 sintered ferrites with compositions x=2.5 to 5 exhibited good microwave absorption properties, with minimum reflection losses (R.L.) less than -20 dB in 1 to 20 GHz frequency range, for matching thicknesses (dm) of 0.5 to 3.8 mm. BaFe12-x(Ti0.5Mn0.5)(x)O-19 ferrite-resin composites with 70 mass% ferrite, exhibited wide bandwidths with R.L. < -20 dB. In particular, the composite samples with compositions x=3 and x=4 had wide bandwidths of 14.1 to similar to 20 GHz and 7.4 to 12.0 GHz, for matching thicknesses of 1.6 mm and 2.7 mm, respectively. These matching thicknesses were smaller than for conventional spinel ferrites. It may be concluded that Barium M-type ferrite is a good candidate for a thin electromagnetic microwave absorber in the GHz range. This is the first study to show that it is possible to use the natural resonance of M-type ferrite for the absorption of microwave radiation.