Size effects in monodomain magnetite based ferrofluids

Ferrofluids based on two types of hybrid particles Fe3O4/β-cyclodextrin were prepared: Using monodomain (below 60 nm) magnetite nanoparticles with (A) non-superparamagnetic (non-SPM) behaviour and (B) with superparamagnetic (SPM) behaviour. We found a strong dependence of the hybrid particles’ magnetic properties on their size and homogeneity. In both types of ferrofluids we observed hyperthermia upon applying an ac electromagnetic field with frequency 40 kHz and amplitude 30 kA/m. The maximal ΔТ upon irradiation with duration of about 12 min for the non-SPM particles was 12 °C, while for the SPM ones it was 3.5 °C.