Nano-structural effects on Hematite (α-Fe₂O₃) nanoparticle radiofrequency heating

Nano-sized hematite (α-Fe₂O₃) is not well suited for magnetic heating via an alternating magnetic field (AMF) because it is not superparamagnetic-at its best, it is weakly ferromagnetic. However, manipulating the magnetic properties of nano-sized hematite (i.e., magnetic saturation (Ms), magnetic remanence (Mr), and coercivity (Hc)) can make them useful for nanomedicine (i.e., magnetic hyperthermia) and nanoelectronics (i.e., data storage). Herein we study the effects of size, shape, and crystallinity on hematite nanoparticles to experimentally determine the most crucial variable leading to enhancing the radio frequency (RF) heating properties. We present the synthesis, characterization, and magnetic behavior to determine the structure-property relationship between hematite nano-magnetism and RF heating. Increasing particle shape anisotropy had the largest effect on the specific adsorption rate (SAR) producing SAR values more than 6 × greater than the nanospheres (i.e., 45.6 ± 3 W/g of α-Fe₂O₃ nanorods vs. 6.89 W/g of α-Fe₂O₃ nanospheres), indicating α-Fe₂O₃ nanorods can be useful for magnetic hyperthermia.