Microwave-absorption properties of FeCo microspheres self-assembled by Al2O3-coated FeCo nanocapsules

FeCo microspheres, self-assembled by Al2O3-coated FeCo nanocapsules, were prepared by means of the arc-discharge technique to investigate application in electromagnetic-wave absorption. For the FeCo microspheres, a reflection loss (RL) exceeding -20 dB was obtained in the frequency range of 10.9-15.6 GHz for an absorber thickness of 1.2-2.0 mm. An optimal RL of -30.8 dB was found at 11.4 GHz for an absorber thickness of 2.0 mm. The excellent microwave-absorption properties are a consequence of a proper electromagnetic match in the microstructure of a strong natural resonance and of the shape anisotropy.