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In this paper, we propose and demonstrate a broadband microwave absorber based on magnetic metamaterial structure elements. We deploy FeCo soft magnetic composite with droplet shape as the primary resonant element. By investigating the resonant modes and the coupling between periodic unit-cells and the incident microwave, it is found the intrinsic magnetic susceptibility of the magnetic elements could make the magnetic field confined in the magnetic element, and thus results in a broadband microwave absorption. Our work provides a new approach to realize broadband microwave absorbers based on hybrid absorption mechanisms, including dielectric resonator effect, one quarter wavelength resonance effect, and grating effect.

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High-contrast gratings (HCGs) based spoof surface plasmon polaritons (SSPPs), as a new kind of SSPPs, have been proposed recently. Here, we study their particular mechanism and characteristics by comparing them with traditional metal-type SSPPs. The different fundamental dielectric resonator modes decided by the height–length ratio R of the dielectric element are found to be the key factor of the mechanism, leading to new characteristics and providing more working modes. In low R mode, HCG-based SSPPs can work under deep-subwavelength thickness and can be easily excited by free space wave and, thus, are considered to be applied to all-dielectric metamaterial absorbers (ADMMAs). Simulations and analysis confirm the microwave absorption effect of HCG-based SSPPs as a new mechanism of ADMMAs. Based on this, a carbon black based ADMMA is designed and the simulation and experimental results verify the important role of HCG-based SSPPs in broadband absorption. It is expected that this work can give rise to further and wider studies on the characteristics and applications of HCG-based SSPPs.