Low-Frequency, Ultra-Thin and Ultra-Wideband Meta-Absorber via Resonance Enhancement Harnessing Magnetic Material.

Achieving efficient, ultra-thin, and broadband absorption in the low-frequency regime (e.g., P to S bands, 0.23-4 GHz) remains a significant challenge due to the inherent limitations of conventional materials and designs. To address this, we propose a composite metamaterial absorber that synergistically integrates a three-layer metasurface absorber (TLMA) with a top-loaded magnetic material (MM) layer. The standalone TLMA achieves perfect absorption (> 90%) but within a narrow 300 MHz band around 0.77 GHz. The introduction of the MM layer drastically enhances and broadens the resonant response through magnetic loss and optimized coupling, yielding an ultra-wide absorption bandwidth from 0.5 to 3.8 GHz, which effectively covers the P, L, and S bands. The final optimized structure exhibits a remarkable overall thickness of only 41.0 mm (0.068λ at the lowest frequency) and a fractional bandwidth of 153.5%. The working mechanism, elucidated through surface current and equivalent impedance analysis, is attributed to magnetic-material-assisted resonance optimization. This work provides a practical and effective strategy for developing high-performance, ultra-thin absorbers for advanced low-frequency applications.