Magnetic properties of chromium (III) oxide nanoparticles

Cr₂O₃ nanoparticles of controlled particle size were prepared by calcination of a precursor, Cr(OH)₃, obtained by precipitation with sodium hydroxide. Samples were characterized by transmission electron microscopy and x-ray diffraction. Average particle sizes ranged from 20 to 200 nm. The magnetic properties of Cr₂O₃ nanoparticles show the presence of a net magnetic moment at the surface due to the large surface/volume ratio. This fact modifies the classical behaviour expected for bulk antiferromagnetic particles. Below the Néel temperature, magnetization curves as a function of the applied magnetic field show the presence of coercive forces in the low-field range.