Investigation of magnetic properties of interacting Fe2O3 nanoparticles

The magnetic properties of Fe2O3 nanoparticles (average diameter O congruen t to 3 nm) in alumina (68% Fe2O3 in weight) have been investigated by magne tization measurements. The results indicate a superparamagnetic behavior of interacting particles, which block with decreasing temperature (the zero-f ield-cooled susceptibility shows a maximum at T congruent to 145 K) with a distribution of relaxation times. A change of magnetic regime is observed b elow similar to 60 K, due to the increasing interparticle interactions and local surface anisotropy. (C) 2001 Elsevier Science B.V. All rights reserve d.