Strong dual-frequency electromagnetic absorption in Ku-band of C@FeNi ₃ core/shell structured microchains with negative permeability

C@FeNi₃ core/shell structured microchains with an average diameter of 400 nm and lengths of about tens microns were synthesized by a simple hydrothermal method. The morphologies, microstructures and electromagnetic properties were investigated by means of scanning electron microscope, transmission electron microscopee, X-ray diffraction, Raman spectroscopy, physical property measurement system and vector network analyzer. C@FeNi₃ core/shell structured microchains were constructed by FeNi₃ alloy submicron spheres with average diameter of 350 nm and carbon shell with thickness about 50 nm. Their electromagnetic properties were investigated in the 2-18 GHz frequency range. The permittivity presented strong dielectric relaxation behavior over 11.5-18 GHz, corresponding to Debye dipolar relaxation. The permeability was found to have negative imaginary parts within 11.5-18 GHz. Strong dual-frequency absorption behavior was observed in the Ku-band due to consequence of interface relaxation.