Structural effects on the magnetic properties of gamma-Fe2O3 nanoparticles

Structural and magnetic properties of gamma-Fe2O3 have been studied in sphe rical nanoparticles. ranging from 3 to 15 nm with a narrow particle size di stribution. Partial, cationic order is observed for particles larger than 1 0 nm in diameter while the smallest ones are disordered. All magnetic prope rties measured showed a strong dependence on the average crystallite size. Saturation magnetisation was found to decrease linearly with decreasing cry stallite size in the ordered samples. However, a stronger decrease was obse rved 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.