New synthesis route for high quality iron oxide-based nanorings: Structural and magnetothermal evaluations

Abstract

The present study reports on the successful fabrication of high quality monocrystallite magnetite (Fe3O4) nanorings, based on the transformation of monocrystallite hematite (α-Fe3O4) nanorings, using a wet and mild-temperature-mediated chemical route, as an alternative to the traditional solid–solid annealing methods. Additionally, attempts to fabricate ferrite-based nanorings with different stoichiometry through metal-ion (Mn2+, Zn2+, Co2+, and Fe2+) doping and using solid–solid reaction by annealing the hematite nanorings is herein reported. The nanoring morphology is confirmed by electron microscopy micrographs whereas typical magnetic vortex signature is revealed in magnetic hysteresis cycle measurements recorded at room temperature, via collapsing of open loop at low magnetic fields. Rietveld refinement analysis revealed fabrication of single-phase (except one sample revealing two phases) and high-quality crystalline nanomaterials, identified with standard ICDD cards. The as-fabricated samples were tested in regard to their performance for magnetic hyperthermia application, using AC magnetic field amplitude of 100, 150, 200, and 240 Oe while setting frequency at 330 kHz. The recorded temperature versus time curves were successfully explained by the Box-Lucas method.