Enhanced microwave absorption properties of Co and Ni co-doped iron (II,III)/reduced graphene oxide composites at X-band frequency

The Co_1−xNi_xFe₂O₄ (x = 0.2, 0.5, 0.8) spinel ferrites were synthesised by sol–gel auto combustion method. The Co_1−xNi_xFe₂O₄/RGO composites were prepared by in situ chemical reduction method and XRD, FTIR, Raman spectroscopy, SEM, VSM and VNA were investigated for crystalline structure and electromagnetic properties. The crystallite size decreases with addition of RGO in ferrites. Magnetization saturation, coercivity and remnant magnetisation decreases with increase of Ni content in the composite with lowest remnant of 9.41 emu/g for 80% of Ni in Co_1−xNi_xFe₂O₄/RGO showing ferromagnetic nature. The complex permittivity and complex permeability of the composites were measured at X-band frequency which shows significant change with addition of RGO. The maximum reflection loss of − 19.56 dB at 10.04 GHz with bandwidth (RL < 10 dB) 2.49 GHz was obtained for Co_0.2Ni_0.8Fe₂O₄/RGO composite with the thickness of 2 mm. The investigations present easy composite preparation of spinel ferrites with graphene oxide and comparison of electromagnetic studies imply the use of Co_0.2Ni_0.8Fe₂O₄/RGO composite as microwave absorber in shielding and communications.