Paramagnetic spin disorder on ferrimagnetic surface and dual dip microwave absorption for hydrothermally synthesized coral shaped NiCo2O4-rGO composite

Nanoparticles of NiCo₂O₄ was synthesized using hydrothermal technique and to enhance the synergistic effect in microwave absorption it was incorporated in reduced graphene oxide (rGO). Recorded X-ray diffractograms and their Rietveld refinement confirmed the desired crystallographic phase formation. Microstructure and morphological information from transmission and scanning electron microscopy ensured the presence of rGO in NiCo₂O₄-rGO phase. Also, morphological features confirmed the presence of nanoparticles of NiCo₂O₄ in the matrix of rGO. Magnetic properties confirmed the paramagnetic spin disorder on the surface of the ferrimagnetic core. Here, the magnetic and non-magnetic component in the nanocomposite have been chosen to ensure enhancement of microwave absorption originated from the tuning of magnetic and dielectric behaviour. Interestingly, the combined contributions of magnetic NiCo₂O₄ and electroactive rGO make this NiCo₂O₄-rGO nanocomposite system a distinctive material for microwave enhancement. Reflection loss property of NiCo₂O₄-rGO nanocomposite has achieved the dual dip reflection loss of −44.49 dB at 15.12 GHz and − 43.61 dB at 15.63 GHz. Incorporation of rGO influences the magnetic anisotropy, increasing the attenuation constant and decreasing the skin depth, which further improves the microwave absorption and broadens the effective bandwidth. The optimisation of wave and matter interaction results the superior reflection loss, making the NiCo₂O₄-rGO system an ideal one for microwave device applications.