Efficient absorption of low-frequency microwaves usually requires heavier weight of Radar Absorbing Materials (RAMs), especially for Magnetic Absorbers (MAs) with large mass density. In this paper, we propose a method of achieving high-efficiency absorption of low-frequency microwaves by modulating local magnetic fields within MAs using Plasmonic Metamaterials (PMs). To this end, we put a periodic array of plasmonic wires on top of MAs to constitute a kind of Plasmonic Metamaterial Absorber (PMA). By adjusting the wire length and the wire-MAs spacing, magnetic fields beneath the wires can be enhanced and more concentrated magnetic field lines are confined within the MAs below, leading to significant absorption enhancement of low-frequency microwaves. To verify this method, we fabricate a prototype of the proposed PMA using a kind of 3.0mm silicone sheet MAs. Both the simulation and experiment results show that the absorption is enhanced significantly and is above 90% in 1.0-2.5GHz under normal incidence, with little addition to the areal density (about 2.2%). Furthermore, the operating angle is also broadened. Even at incident angle 75°, the -10dB bandwidth is 1.17-3.42GHz. Due to little weight addition, high-efficiency and wideband absorption can be realized. This design method may find potential applications in fields such as radar stealth, electromagnetic compatibility and communication.
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