Size dependence of the magnetic moments of exposed nanoscale iron particles

The magnetic moments in exposed, mass-selected, nanoscale Fe clusters in th e size range 1.89-2.20 nm (300-475 atoms), deposited onto graphic in situ h ave been measured by X-ray magnetic circular dichroism. The smallest cluste rs possess moments that are enhanced by around 4% for m(spin) and 80% for m (orb) and decrease towards the bulk value with increasing size. The larger clusters show an in-plane anisotropy that is consistent with the anisotropy in the orbital moment. The smallest clusters are, within experimental erro r, magnetically isotropic. The anisotropy constant in the 475-atom clusters is significantly higher than the bulk value. (C) 2001 Elsevier Science B.V . All rights reserved.