Effect of post annealing process on structural, magnetic and spin dynamics properties of MnFe2O4 nanoparticles

Abstract

The present research work focuses on the one-step and cost-effective hydrothermal synthesis and characterization of manganese ferrite (MnFe2O4) magnetic nanoparticles (MNPs). To investigate the effect of different annealing temperatures on the structural, magnetic and spin dynamics properties of the as-synthesized MNPs, samples were annealed at 200°C, 400°C, and 600°C. X-ray diffraction (XRD) analysis showed that all samples had a cubic spinel phase structure with space group Fd-3 m (227), with minor impurities of α-Fe2O3 and α-Mn2O3 phase are present. The average crystallite size of the MNPs increased with increasing annealing temperature, due to grain growth. The molecular dynamics, bond stretching, and cubic spinel phase of all samples were analyzed through IR spectroscopy. Furthermore, the post-annealing process resulted in a decrease in saturation magnetization from 44.04 emu/g to 29.01 emu/g, which increased to 33.79 emu/g as the annealing temperature was raised from 200°C to 400°C and further to 600°C. Ferromagnetic resonance spectroscopy was utilized to validate the magnetic characteristics, unveiling the presence of unpaired electrons and assessing the resonant magnetic field, g-factor and peak-to-peak line width.The broad resonance signal observed in the room temperature spin dynamics indicated a strong dipolar-dipolar interactions interaction between magnetic ions through oxygen ions. The obtained results indicate that the synthesized MnFe2O4 MNPs have the potential to be used in various biomedical applications, including targeted drug delivery and magnetic hyperthermia treatment, owing to their biocompatibility, excellent magnetic properties, and facile synthesis method. This study paves the way for further research on the applications of MnFe2O4 MNPs in the field of nanomedicine.