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NiFe 2 O 4 nanosheets have been synthesized via a simple surfactant-assisted solution route, which are confirmed by X-ray powder diffraction, scanning electron microscopy and transmission electron microscopy. The NiFe 2 O 4 sample exhibits the sheet-like structure, with width varying from 200 to 800 nm and thickness ranging from 20 to 60 nm. The electromagnetic properties of NiFe 2 O 4 nanosheetsparaffin composites have been deeply investigated. The multiple dielectric relaxation loss in NiFe 2 O 4 nanosheets is attributed to the size distribution and morphology of the NiFe 2 O 4 nanosheets. The magnetic loss in the present system is caused mainly by the natural resonance. An absorber with a thickness of 4.3 mm exhibits an optimal reflection loss (RL) value of -47.1 dB at 7.67 GHz. RL values exceeding -20 dB in the 2.68-17.96 GHz range are obtained by choosing an appropriate absorptionlayer thickness between 1.9 and 10 mm. Not only the RL peak frequency but also the number of the peaks can be well explained by the quarter-wavelength cancellation model.