Nanoneedles of maghemite iron oxide prepared from a wet chemical route

Nanometer-sized maghemite iron oxide (γ-Fe₂O₃) particles were produced first by synthesis of a precursor, γ-FeO(OH), in a surfactant-less microemulsion and subsequent heat treatment of the γ-FeO(OH). The precursors and γ-Fe₂O₃ powder were characterized using thermogravimetric analysis (TGA), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Susceptometer from Quantum Design (SQUID) measurements. TGA and XRD analysis indicated the formation of single cubic phase when the samples were heat-treated at 240°C. TEM reveals that the γ-Fe₂O₃ particles are needle-shaped with an aspect ratio of ∼ 20; typically 5-10nm wide and over 150nm long. It was found that these microemulsion-derived γ-Fe₂O₃ nanoneedles possess an intrinsic coercivity of 28Oe at 300K and 950Oe at 2K.