Size Dependence of Ferrimagnetic MgFe2O4 Nanoparticles on AC Magnetically-Induced Heating Characteristics in Powder and Fluidic States

Abstract

Alternating current (AC) magnetically-induced heating characteristics of MgFe2O4 ferrimagnetic nanoparticles (FMNPs) are investigated in both powder and ferrofluidic states for efficient hyperthermia agent applications. To obtain different sizes and size distributions of MgFe2O4 FMNPs, ball milling process (ball diameters: 3 mm and 5 mm) is carried out during the modified sol-gel method. The MgFe2O4 FMNPs formed with 3 mm-ball milling process have the smallest particle size and narrowest size distribution. These FMNPs provide the lowest AC magnetically induced heating temperature (T-AC,T-mag, Delta T = 65 degrees C) in powder state. However, it generates the highest T-AC,T-mag (Delta T = 5.1 degrees C) and specific loss power (SLP, 525 W/g) in fluidic state at a low frequency (f(appl) = 110 kHz) and a magnetic field (H-appl = 140 Oe). It was also observed that the hysteresis loss and relaxation loss were crucial parameters for heating mechanism of FMNPs in ferrofluids. These loses depends on coating conditions and dipole interaction, which in turn are closely related to the particles size and its distribution. In addition, it was also determined that the weaker magnetic dipole interaction in the ferrofluid FMNPs, enhanced the relaxation loss and hysteresis loss, leading to an improvement of the AC heat generation characteristics.