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 −20dB was obtained in the frequency range of 10.9–15.6GHz for an absorber thickness of 1.2–2.0mm. An optimal RL of −30.8dB was found at 11.4GHz for an absorber thickness of 2.0mm. 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.