Synthesis, magnetic and electromagnetic properties of Al2O3/Fe oxides composite-coated polyhedral Fe core–shell nanoparticles

Polyhedral Fe nanoparticles with amorphous Al2O3/FeOx composites shells are prepared by the arc discharge method, in which the shape of Fe nanoparticles includes quadrilateral, pentagon, hexagonal and sphere. Magnetic and electromagnetic (EM) properties of Fe nanoparticles have been investigated in detail. Reflection loss (RL) values exceeding −10 dB are calculated in 7–18 GHz for an absorber thickness of 1.6 mm, and RL values exceed −5 dB at 2–18 GHz for any absorber thickness between 3.8 and 10 mm. An optimal RL value of −38.46 dB is observed at 6.2 GHz with a matching thickness of 2.3 mm. The excellent EM properties are ascribed to the dielectric resonance from the special core–shell microstructure and the broad and strong natural resonance from the shape anisotropy of Fe nanoparticles.