BARIUM M-TYPE FERRITE AS AN ELECTROMAGNETIC MICROWAVE ABSORBER IN THEGHZ RANGE

The electromagnetic microwave absorption properties of Barium M-type f errite, in which Fe3+ was substituted by (Ti0.5Mn0.5)(3+), were invest igated in the GHz frequency range. The anisotropy field (H-A) of Bariu m M-type ferrite can be changed by varying the Ti0.5Mn0.5 content, whi ch enables the natural resonance frequency (fr) to be controlled, in t he range 48 GHz to 8 GHz. BaFe12-x(Ti0.5Mn0.5)(x)O-19 sintered ferrite s with compositions x=2.5 to 5 exhibited good microwave absorption pro perties, with minimum reflection losses (R.L.) less than -20 dB in 1 t o 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 bandwidt hs of 14.1 to similar to 20 GHz and 7.4 to 12.0 GHz, for matching thic knesses of 1.6 mm and 2.7 mm, respectively. These matching thicknesses were smaller than for conventional spinel ferrites. It may be conclud ed that Barium M-type ferrite is a good candidate for a thin electroma gnetic 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 ferri te for the absorption of microwave radiation.