Formation mechanism of nano-crystalline β-Fe₂O₃particles with bixbyite structure and their magnetic properties

Abstract

Formation mechanism of nano-crystalline β-Fe2O3 particles was investigated by controlling the preparation conditions such as the mixing ratio of NaFe(SO4)2 to NaCl and heating treatment temperature. A single phase of β-Fe2O3 was formed regardless of the mixing ratio. The heat treatment temperature strongly affected the particle shapes and sizes. Below 490 °C, they had granular shape with a diameter of about 50 to 100 nm. While, above 490 °C, cubic particles with increased size of about 1 μm were produced. All samples were antiferromagnetic at low temperature. The Néel temperature (TN) of 119 K for the large cubic particles was decreased to 113 K for the nanoparticles.