Dynamic behavior of superparamagnetic iso-oriented magnesioferrite nanoparticles

Small magnetic particle systems generally present complex magnetic behaviors, which are due to the similarity of effects arising from distribution of size, shape, orientation of anisotropy axis and interparticle interactions that can jeopardize the comparison between experimental results and theoretical models. The system formed by magnesioferrite (MgFe(2)O(4)) nanoparticles precipitated in dilute solid solutions of iron in MgO (magnesiowustite) is interesting since the insulating single crystal matrix impose nanoparticles iso-orientation, and the interparticle interactions are negligible. In addition it is easy to change its average particle size by sample annealing. In this work, we present some dynamic magnetic properties of this system and its relation with the evolution of the average particle sizes with annealing time. (c) 2006 Elsevier B.V. All rights reserved.