Size dependent heating ability of CoFe2O4 nanoparticles in AC magnetic field for magnetic nanofluid hyperthermia

We investigated the size dependent magnetic properties and heating mechanism of spinel CoFe2O4 nanoparticles, which synthesized using the nonhydrolytic thermal decomposition method. The size of CoFe2O4 nanoparticles was arranged with the variation of solvent type, reflux time, and reflux temperature. The optimum size range was determined for magnetic fluid hyperthermia. The particles with 9.9 +/- 0.3 nm average diameter have the highest heating ability in the AC magnetic field having 3.2 kA/m amplitude and 571 kHz frequency. The maximum specific absorption rate of 22 W/g was obtained for 9.9 +/- 0.3 nm sized CoFe2O4 nanoparticles. The calculations and experimental results showed the dominancy of Brownian relaxation at the heat production of synthesized 9.9 +/- 0.3 nm nanoparticles. In contrary, the magneto-heating in 5.4 +/- 0.2 nm particles mainly originated from Neel relaxation.