High coercivity α-Fe2O3 nanoparticles prepared by continuous spray pyrolysis

Abstract

Surfactant free growth of α-Fe₂O₃ nanoparticles by continuous spray pyrolysis (CoSP) resulted in high coercivity (H_C). X-ray diffraction (XRD), Raman spectroscopy, and Fourier transform infrared spectroscopy (FT-IR) confirmed the formation of pure α-phase of Fe₂O₃. Scanning electron microscopy (SEM) showed a dimpled-morphology in samples grown at ≥800 °C. XRD, SEM, Transmission electron microscopy (TEM) and temperature dependent magnetization data provided evidence of the presence of a sub-structure in the α-Fe₂O₃ particles. The Morin transition in the sample grown at 1000 °C is observed at 245 K with high coercivity (H_C) ∼ 6 kOe at 300 K, which is among the highest reported in the literature. At 10 K, H_C ∼ 10 kOe was observed for α-Fe₂O₃ grown at 600 °C which is also the highest coercivity reported in the literature. This remarkably high H_C observed at low temperature correlates with the enhanced role of surface spins due to the surfactant free growth technique employed in the present work.