Nanometer size clusters and particles: a comparative study of magnetic behavior

The magnetic properties of large iron-oxo clusters stabilized within a shell of organic ligands and silica-coated or polymer-supported iron-oxide nanoparticles have been studied via Mossbauer spectroscopy. We make use of the clusters' core/shell interface X-ray structural characteristics to shed light on atomic coordination distortions that may be imposed at the particle/matrix interface. Interface strains of 7% or larger are inferred which could induce atomic surface reconstruction and concomitant large surface and strain contributions to the magnetic anisotropy density, producing K similar to 10(5) J/m(3). (C) 2003 Elsevier B.V. All rights reserved.