Structural effects on the magnetic properties of γ-Fe2O3 nanoparticles

Structural and magnetic properties of gamma-Fe2O3 have been studied in spherical nanoparticles. ranging from 3 to 15 nm with a narrow particle size distribution. Partial, cationic order is observed for particles larger than 10 nm in diameter while the smallest ones are disordered. All magnetic properties measured showed a strong dependence on the average crystallite size. Saturation magnetisation was found to decrease linearly with decreasing crystallite size in the ordered samples. However, a stronger decrease was observed in the disordered samples, suggesting that,both Surface and structural characteristics are needed in order to explain the magnetic properties of nanoparticles. (C) 1999 Elsevier Science B.V. All rights reserved.