Particle size-dependent magnetic properties of γ-Fe2O3 nanoparticles

The effect of particle size on the magnetic properties of nano-crystalline powders of gamma-Fe2O3 has been studied, using a DC magnetization technique, as a function of temperature and magnetic field. A superparamagnetic-type blocking process is observed in the ZFC and FC magnetization. Coercivity increases with increasing particle size, while the saturation magnetization decreases with increasing particle size. Such anomalous behaviour can be explained in terms of the redistribution of Fe3+ ions, depending on the particle size. (C) 2003 Elsevier B.V. All rights reserved.