Magnetic properties of chromium (III) oxide nanoparticles

摘要

Cr_2O_3 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 Cr_2O_3 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 Neel temperature, magnetization curves as a function of the applied magnetic field show the presence of coercive forces in the low-field range.