Abstract
We report a comparative study of the heating response of hematite (alpha-Fe2O3) and NiFe2O4 nanoparticles under an alternating magnetic field. In addition, Langevin model and the law of approach to saturation (LAS) are used to confirm the magnetic behavior and to determine the effective anisotropy constant (K-eff). Magnetic measurement at room temperature showed superparamagnetic behavior for both samples. This behavior is corroborated by the successfully fitting into Langevin function for paramagnetic materials. We find that alpha-Fe2O3 nanoparticles has high saturation (2.46 emu/g) compared to the bulk value and Keff (3.12 x 10(3) erg/cm(3)), while saturation and K-eff for NiFe2O4 nanoparticles are 18.8 emu/g and 2.8 x 10(4) erg/cm(3) respectively. The specific absorption rate (SAR) is investigated under an alternating magnetic field and as a function of concentration (5,10,20 mg/mL) and amplitude of the applied magnetic field (90,130, 1700e).The SAR and intrinsic loss power (ILP) values obtained for both samples indicated best heating of NiFe2O4 nanoparticles compared to alpha-Fe2O3 nanoparticles. We showed also that both samples did not reach hyperthermia temperature (42 degrees C) but maintain a good temperature rise and the SAR values follows linear response theory (LRT). Finally, the contribution of each mechanism in the heat dissipated by alpha-Fe2O3 and NiFe2O4 nanoparticles were investigated.