Surfactant-assisted synthesis of α-Fe2O3 nanotubes and nanorods with shape-dependent magnetic properties

alpha-Fe2O3 nanorods and nanotubes have been synthesized and characterized by high-resolution transmission electron microscopy and X-ray diffraction. By means of different surfactant assistance, the high-quality one-dimensional products were obtained, respectively, with aqueous butanol solution as the solvent and carbamide as the base, giving rise to single-crystalline products at 150 C. The formation mechanism has been presented. Significantly, the magnetic investigations show that the magnetic properties are strongly shape-dependent; i.e., the nanorods have a Morin transition at 166 K from canted antiferromagnetic state to antiferromagnetic state, while the nanotubes exhibit a three-dimensional magnetic ordering above 300 K that has been attributed to the presence of small particles in a few regions of the tubes.