Microwave dielectric and magnetic properties of superparamagnetic 8-nm Fe3O4 nanoparticles

The superparamagnetic 8-nm Fe3O4 nanoparticles were successfully prepared by chemical oxidation process. For the complex permittivity, the dual dielectric relaxation processes have been proved by two overlapped Cole–Cole semicircles, and the natural resonance frequency is 3.03 GHz for the complex permeability. The maximum reflection loss value reaches −55.5 dB at 6.11 GHz with 3.85 mm in the thickness of the absorbers for the superparamagnetic 8-nm Fe3O4 nanoparticles which is better than that of 150 nm and 30 nm Fe3O4 nanoparticles. It is believed that the superparamagnetic 8-nm Fe3O4 nanoparticles can be used as a kind of candidate for microwave absorber.

► Superparamagnetic 8-nm Fe3O4 nanoparticles synthesized by the simple chemical oxidation.
► The dual dielectric relaxation processes have been proved by the two overlapped Cole–Cole semicircles for the complex permittivity.
► The natural resonance frequency is 3.03 GHz which is larger than the one of 150 nm and 30 nm Fe3O4 nanoparticles.
► These possess better microwave absorption properties than 150 nm and 30 nm Fe3O4 nanoparticles.