Thin electromagnetic wave absorber for quasi-microwave band containing aligned thin magnetic metal particles

TLDR

Soft magnetic material with 2 μm thick amorphous metal flakes aligned perpendicular to wave propagation has been produced. The study aims to design a thin wave absorber by incorporating a low‑permittivity region such as free space into the metal‑filled polymer. The absorber is realized by embedding a free‑space region within the material, lowering average permittivity and balancing complex permeability and permittivity to reduce reflection. The material achieves two‑to‑three‑fold higher permeability than spinel ferrite, and the 3‑mm absorber with 5 % free‑space volume attains over 30 dB reflection loss in the quasi‑microwave band.

Abstract

Soft magnetic material has been produced in which flaky thin amorphous metal particles, about 2 /spl mu/m thick, are aligned in polymer in the direction perpendicular to electromagnetic wave propagation. This material yields a permeability two to three times higher than the spinel-type ferrite system in the quasi-microwave band. We have designed a thin wave absorber composed of the present material by introducing a low-permittivity area such as a free space into the present metal-containing material. This decreases the average permittivity, striking a balance between complex permeability and permittivity values, and thus reducing the reflection coefficient of the absorber. A thin (about 3-mm thick) wave absorber with a reflection loss of over 30 dB in the quasi-microwave band was successfully obtained when the free space region was 5% of the total volume.