Size and Concentration Effects on High Frequency Hysteresis of Iron Oxide Nanoparticles

High-frequency hysteresis measurements were performed on two different types of hydrosols of iron oxide particles: fully dispersed and highly clustered. The fully dispersed sol showed superparamagnetic behavior across the frequency range investigated, while the clustered sample exhibited significant hysteresis. The hysteretic losses were then directly related to magnetic hyperthermia measurements in a sinusoidal field of amplitude 10 mT at 140 kHz, where the clustered sample heated by up to 25degC in 1000 s while the dispersed sample at similar concentration showed no measurable heating.