The synthesis and magnetic properties of nanosized hematite (alpha-Fe2O3) particles.

The synthesis of nanosized superparamagnetic hematite particles by dissolving ferric salts in hydrochloric acid and heating at 100 degrees C is described. A hydrolysis reaction causes the formation of hematite particles. The influence of the sequence of additions on the resulting precipitates was studied using TEM and XRD. The magnetic behavior was characterized by magnetization measurements. It was found that small changes in the reaction conditions led to remarkable changes in final size and shape of the hematite crystallites. A well-defined subrounded morphology and an average diameter of 41 nm were obtained for superparamagnetic hematite particles. This is the largest size reported thus far for superpara-magnetic hematite particles.