Particle interaction effects in antiferromagnetic NiO nanoparticles

Previous studies of the magnetic properties of antiferromagnetic NiO nanopa rticles have mainly been performed on strongly aggregated particles without taking the effects of inter-particle interactions into account. To address this problem we demonstrate that by treating such samples with low-energy ball milling it is possible to physically separate the particles without in ducing changes in the particle size and shape. Both as-prepared and separat ed NiO nanoparticles, with and without Fe-57 doping, have been studied by M ossbauer spectroscopy and magnetisation measurements. Were, we show that in ter-particle interactions can have a strong effect on the superparamagnetic relaxation behaviour of NiO nanoparticles. (C) 2000 Elsevier Science B.V. All rights reserved.