Dynamic Hysteresis Measurement of Magnetic Nanoparticle Suspensions in Parallel and Perpendicular DC Magnetic Fields

The effect of a dc bias magnetic field on the dynamic magnetization process was examined to evaluate the enhancement in the heating ability of magnetic nanoparticle (NP) suspensions for magnetic hyperthermia and the possibility of combination therapies. A dc magnetic field may be used with a combination of magnetic resonance imaging (MRI) and magnetic drug delivery techniques during magnetic hyperthermia. Measuring dynamic magnetization curves under an alternating magnetic field (AMF) is another technique to understand the heating mechanism in hyperthermia. The dynamic magnetization curves were measured under an AMF at frequencies between 50 and 200 kHz with a maximum amplitude ( \mu _{0}H_{0} ) of 70 mT. A dc bias magnetic field ( \mu _{0}H_{\mathrm {dc}} ) of up to 50 mT was applied parallel and/or perpendicular to the AMF. Two NP suspensions were measured; one is a commercially available superparamagnetic (SPM) suspension, Resovist ® (Ferucarbonate), and the other is SCF-3, which is composed of spherical ferromagnetic Co substituted Fe 3 O 4 NPs and shows ferromagnetic characteristics in its dried form. When a dc magnetic field (dc-MF) was applied perpendicular to the AMF, the loop areas decreased more gradually than when a parallel dc-MF was applied. It is concluded that the relaxation behaviors of magnetic suspensions are responsible to the reduction in loop areas by an external dc-MF based on a comparison with the ferromagnetic NP suspension.