Nanoneedles of maghemite iron oxide prepared from a wet chemical route

Nanometer-sized maghemite iron oxide ({gamma}-Fe{sub 2}O{sub 3}) particles were produced first by synthesis of a precursor, {gamma}-FeO(OH), in a surfactant-less microemulsion and subsequent heat treatment of the {gamma}-FeO(OH). The precursors and {gamma}-Fe{sub 2}O{sub 3} 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 deg. C. TEM reveals that the {gamma}-Fe{sub 2}O{sub 3} particles are needle-shaped with an aspect ratio of {approx}20; typically 5-10 nm wide and over 150 nm long. It was found that these microemulsion-derived {gamma}-Fe{sub 2}O{sub 3} nanoneedles possess an intrinsic coercivity of 28 Oe at 300 K and 950 Oe at 2 K.