Dielectric response of a hybrid nanofluid containing fullerene C60 and iron oxide nanoparticles

•Transformer oil based on gas-to-liquid technology is used as ananofluid carrier liquid.•The synthesized nanofluids contain fullerene C60 and iron oxide nanoparticles.•Frequency domain dielectric spectroscopy is applied to study the dielectric response of the nanofluids.•The dielectric response of iron oxide nanoparticles dominates the dielectric spectrum of the hybrid nanofluids.•Without the magnetic nanoparticles, the spectrum of the fullerene-based nanofluid resembles the one of the transformer oil.