Reduced graphene oxide (rGO) sheets were anchored onto quaternary Co0.5Mn0.3Cu0.2Fe2O4 spinel nanoferrite through a one-pot solvothermal route to tailor its microwave-absorption behaviour. X-ray diffraction confirmed that the cubic lattice survives up to 40 wt % rGO, and FE-SEM/XPS revealed a uniform 23 ± 4 nm grain layer decorating the corrugated carbon substrate. Systematic dilution by the non-magnetic rGO lowered the saturation magnetisation from 80.1 to 64.4 emu g−1, a level that still ensures efficient impedance matching by softening the magnetic core. Dielectric loss and interfacial polarisation contributed by rGO widened the absorption window: with only 2 mm thickness, the 30 wt % composite attained a minimum reflection loss of −39.4 dB at 11.5 GHz and offered a 6.8 GHz effective bandwidth (RL < −10 dB), compared with −11.4 dB and 2.5 GHz for pristine ferrite. Owing to its bulk density of 3.2 g cm−3 and absence of rare-earth elements, the material provides a lightweight, scalable and economically attractive route to broadband electromagnetic-interference shields and stealth coatings.
