Herein, xFe2O3/(1 − x)Fe3O4 ferrofluid nanocomposites (0.0 ≤ x ≤ 1.0) prepared by sonochemical method. XRD confirms the formation of two separate phases with average crystallite size in the range of 12–30 nm. The crystallite size varies with the hematite weight fraction x (wt%) and shows smallest size at x = 0.2. FTIR indicates that the band at 627 cm− 1 could be refer to the Fesingle bondO stretching vibrations and the band at 535 cm− 1 could be assigned to Fesingle bondO in Fe2O3. HRTEM and FESM show the spherical and rod-like shape of magnetite and hematite respectively with average particle size of 12 nm for Fe3O4 NPs and 11 nm for Fe2O3 NPs. XRF confirms that nominal and chemical compositions are close. VSM indicates that the prepared ferrofluid nanocomposites exhibit almost superparamagnetic behavior. The magnetic parameters vary with the weight fraction x (wt%), in addition to superior magnetic responsively with the saturation magnetization value a rising from 0.74 to 67.86 emu/g. Analytical thermal analysis techniques exhibit that the ferrofluid nanocomposites show a high degree of thermal stability; also the composition 0.2 shows different behavior and superior properties. Therefore, this composition considered as the aspect ratio for hyperthermia purposes. The behavior of nano-composite (0.2Fe2O3/0.8Fe3O4) for hyperthermia was checked primary by using homemade induction coil at tested frequency of 50 Hz. It found that, 50 Hz frequency induced hyperthermia temperature of about 43 °C at very low magnetic (30 μT) field within 20 min. Finally, we recommend this nanocomposite due to its high magnetization, thermal stability and acceptable biocompatibility for hyperthermia purposes.