Abstract
The RE-Fe-B (RE=Rare earth) compounds have a possibility to be used as electromagnetic (EM) wave absorption materials in the GHz range, because of their high saturation magnetization and large anisotropy field. This paper describes the natural resonance phenomena and the EM wave absorption properties of Sm-substituted Y2Fe14B resin composites, which were measured in the GHz frequency range. The (Y1-xSmx)2Fe14B powders showed an uniaxial anisotropy in the samples of x=0 to 0.12, and their anisotropy fields decreased with increasing x value. However, the easy axis of magnetization changed to basal plane in the samples of x> 0.15. The natural resonance frequency (fr) of the sample with x=0, was calculated as 51.0 GHz from its anisotropy field. The calculated fr value showed a tendency to decrease with increasing x value and exhibited a minimum value of 20.8 GHz in the sample of x=0.15. The magnetic resonance phenomenon were observed in the epoxy resin composites of these powders, and the resonance frequencies showed a good agreement with their calculated f, values. The x=0.10 sample absorbed the EM wave over 99% at 22 GHz with the thickness of 0.69 mm, which is 30% thinner than that of the M-type ferrite/resin absorber. It can be considered that the sample can function as an electromagnetic wave absorber at frequencies around 22 GHz, where one kind of wireless LANs is now planned.
