Development of Flexible Sendust Composite Sheets With Enhanced Magnetic Permeability for Microwave Absorbers and Antennas

The demand for high-frequency soft magnetic composites with elevated permeability and flexibility is growing for applications in microwave absorbers and magnetodielectric antennas. However, balancing high permeability with mechanical flexibility remains challenging. This study presents flexible Sendust (FeSiAl) composite sheets, fabricated with a hot-pressing technique that aligns flakes within an acrylic rubber and epoxy resin matrix. The alignment significantly enhances relative permeability at high frequencies, achieving single-layer film properties of $\mu _{r} ^{\prime } =14.8$ and $\mu _{r} ^{\prime \prime } =20.4$ at 1 GHz, alongside high saturation magnetization (118 emu/g) and high hesitivity (44.7 k $\Omega \text {m}^{-1}$ ), outperforming commonly used materials such as NiZn ferrite. Our method supports customizable thickness without sacrificing permeability, establishing a versatile platform for advanced conformal microwave absorber and antenna applications.