Cobalt-doped CoxMn1-xFe2O4/SWAC composites for ultra-thin and high-performance electromagnetic wave absorption

The intensifying electromagnetic pollution in the 5G era urgently demands the development of highly efficient electromagnetic wave (EMW) absorbing materials. This study employs a surfactant-assisted solvothermal method, utilizing methylene blue-saturated woody activated carbon (SWAC) as a sustainable carbon matrix, to successfully synthesize a series of cobalt-doped Co x Mn 1-x Fe 2 O 4 /SWAC composites with tunable molar ratios. By optimizing the Co/Mn molar ratio, the composite exhibits outstanding microwave absorption performance at an ultra-thin thickness of just 1.34 mm when x = 0.6: minimum reflection loss (RL min ) reaches −55.67 dB, and effective absorption bandwidth (EAB) spans 2.16 GHz (15.84–18 GHz). Its matched thickness was significantly reduced by 57% compared to the control sample. The performance enhancement stems from multiscale synergistic effects induced by cobalt doping: cobalt enhances hysteresis loss and optimizes the natural resonant frequency; the difference in ionic radii between Co 2+ and Mn 2+ ions induces lattice distortion, promoting interfacial polarization. These mechanisms collectively optimize the material's impedance matching and attenuation capabilities, realizing a synergistic magnetoelectric loss mechanism. This study provides a novel strategy for designing lightweight, high-performance, and sustainable broadband electromagnetic wave absorbers.