Nanorods of iron oxalate synthesized using reverse micelles: facile route for α-Fe₂O₃ and Fe₃O₄ nanoparticles

Abstract

Uniform and smooth nanorods of iron oxalate dihydrate have been synthesized using the reverse micellar route in the presence of the cationic surfactant CTAB (cetyltrimethyl ammonium bromide). These rods have an average diameter of 70nm and length of 470nm and show an antiferromagnetic ordering at 27 K. The oxalate rods act as suitable precursor for obtaining a variety of iron oxide nanoparticles depending on the nature of the atmosphere in which decomposition is performed. Spherical α-Fe₂O₃ nanoparticles (~50 nm) were obtained when the nanorods were decomposed in air (500 °C) and show a transition from a weakly-ferromagnetic to weakly anti-ferromagnetic behaviour at ~225 K which is reminiscent of a Morin-like transition. Cuboidal Fe₃O₄ nanoparticles (~60-70 nm) were obtained by the decomposition at 500 °C in vacuum (~10⁻⁵ torr) and show a Verwey transition at 122 K.