Synthesis of magnetic nickel ferrite microspheres and their microwave absorbing properties

NiFe₂O₄ microspheres were synthesized using a solvothermal method. The morphologies and structures of NiFe₂O₄ micropheres were characterized using a field emission scanning electron microscope(FESEM), a transmission electron microscope(TEM) and an X-ray diffractometer(XRD). The NiFe₂O₄ microspheres were around 150―200 nm in diameter and assembled by nanoparticles. The magnetic and electromagnetic parameters were measured using a vibrating sample magnetometer and a vector network analyzer, respectively. The obtained products exhibited a saturation magnetization of 60.8 A·m²·kg^–1 at room temperature. A minimum reflection loss(RL) of–27.8 dB was observed at 9.2 GHz with a thickness of 3.5 mm, and the effective absorption frequency(RL<–10 dB) ranged from 8.2 GHz to 11.2 GHz, indicating the excellent microwave absorption performance of the NiFe₂O₄ microspheres in the X-band frequencies.