Physical Parameters to Enhance AC Magnetically Induced Heating Power of Ferrite Nanoparticles for Hyperthermia in Nanomedicine

Solid-state ferrimagnetic MFe₂O₄ (M = Mg, Ni, Co; mean diameter size d = 30-35 nm) and superparamagnetic MFe₂O₄ (M = Mg, Ni, Mn_0.5Zn_0.5; d = 6-8 nm) nanoparticles [ferromagnetic nanoparticles (FMNPs) and superparamagnetic nanoparticles (SPNPs)] were used to explore the physical mechanisms of ac magnetically induced heating and identify what physical parameters would be the most critical to enhance the ac magnetically induced heating power for local in vivo hyperthermia agent applications. It was experimentally confirmed that “dc (minor) hysteresis loss power” generated by the magnetization reversal process, and “Néel relaxation loss power” generated by fluctuation of the magnetic moment dominantly contribute to the ac heat generation of FMNPs and SPNPs, respectively. In addition, all the experimentally and physically analyzed results demonstrated that the improvement of in-phase magnetic susceptibility χ´m is directly relevant to the “dc (minor) hysteresis loss power” as well as the dc magnetic softness, and the out-of-phase magnetic susceptibility χ^´´m is directly relevant to the “Néel relaxation loss power (or ac magnetic hysteresis loss power, A )” as well as the ac magnetic softness are the most crucial physical parameters responsible for enhancing the ac magnetically induced heating power of solid-state FMNPs and SPNPs, respectively. Particularly, some technical and engineering approaches, which can improve the χ´m of FMNPs and the χ^´´m of SPNPs, were proposed and introduced in this study to provide crucial information how to effectively design and develop a new promising hyperthermia agent in nanomedicine.