Synthesis of exchange coupled nanoflowers for efficient magnetic hyperthermia

•Magnetic nanoflowers of MnFe2O4 (as seed) and γ-Fe2O3 were successfully synthesised.•Three-fold increase in the ILP values for nanoflowers than single-core MNPs.•The nanoflowers were found to be biocompatible even at higher concentrations ∼3 mg/mL.•Magnetic hyperthermia with 0.75 mg/mL of nanoflowers decreased HeLa cells viability to 17%.