Single-phase and binary phase nanogranular ferrites for magnetic hyperthermia application

The study demonstrates the performance of heating efficiency in single-phase and binary phase spinel ferrite nanosystems. Ferrimagnetic cobalt ferrite (CoFeO) (CFO) and superparamagnetic copper ferrite/copper oxide (CuFeO/CuO) (CuF) nanosystems of different particle sizes were synthesized through a microwave-assisted coprecipitation method. The heating behavior was observed in range of both field amplitudes (8-24 kA/m at 516 kHz) and frequencies (325-973 kHz at 12 kA/m). The heating efficiency was analyzed and compared by means of particle size, magnetization, effective anisotropy constant, and Néel relaxation mechanism. Indeed, the heating rate was maximized in larger ferrite particles with low effective anisotropy constant. Moreover, though the magnetization and effective anisotropy constant of single-phase CoFeO nanoparticles were higher, the binary phase CuFeO/CuO nanosystems of similar crystallite size (28 nm) exhibited superior heating efficiency (4.21°C/s). For a field amplitude and frequency of 24 kA/m and 516 kHz, the heating rate of CuF and CFO ferrites with different crystallite sizes decreased in the order of 4.21 > 2.14 > 0.58 > 0.52°C/s for 29 nm > 25 nm > 12 nm > 15 nm, respectively. The results emphasize that binary phase ferrite nanoparticles are better thermoseeds than the single-phase ferrites for the magnetic hyperthermia application.
The authors greatly acknowledge FONDECYT Postdoctoral Research Project No.: 3160170, CONICYT PIA/APOYO CCTE AFB170007 and CONICYT BASAL CEDENNA FB0807, Government of Chile and FAPESP Postdoctoral Fellowship Process Number (2018) 19096-1, FAPESP thematic project number: 2017/10581-1, CNPq Grant number: 310230/2017-9, and FAPEG Grant number: 201710267000511, Government of Brazil for financial assistance