The effect of interparticle interactions on spin glass and hyperthermia properties of Fe₃O₄ nanoparticles

Water dispersible Fe₃O₄ nanoparticles (NPs) were prepared, forming a durable suspension for several days. The zero field cooled magnetization peak temperature is ∼4.5 times larger than the average blocking temperature, suggesting the presence of interparticle interactions. Frequency dependent AC magnetic susceptibility revealed superspin glass state at low temperatures. Also a signature of size dependent surface spin glass state was observed associated with a hump in in-phase and a peak in out-of phase susceptibility curves. Magnetic hyperthermia studies indicated that interparticle interactions influence the heat generation of NPs in an AC magnetic field. The temperature rise of 7 nm particles obtained was 8 times larger than that of 5 nm particles. This study shows the important role of interparticle interactions on magnetic and hyperthermia properties of magnetic NPs. (paper)