AVS 49th International Symposium
    Magnetic Interfaces and Nanostructures Monday Sessions
       Session MI+NS-MoA

Paper MI+NS-MoA9
Evolution of Fe Nanocluster Magnetism Grown on Pt(111)

Monday, November 4, 2002, 4:40 pm, Room C-205

Session: Self-Assembly and Nanomagnetism
Presenter: P. Bencok, European Synchrotron Radiation Facility, France
Authors: P. Bencok, European Synchrotron Radiation Facility, France
S.S. Dhesi, European Synchrotron Radiation Facility, France
P. Ohresser, Laboratoire pour l'Utilisation du Rayonnement Electromagnétique, France
N. Brookes, European Synchrotron Radiation Facility, France
Correspondent: Click to Email
The magnetic structure of nanoparticles is a fascinating research area with many new and unexpected results. For the preparation of nanostructures one may use a well chosen system with appropriate growth modes. Room temperature deposition of submonolayer Fe ultrathin films on Pt(111) results in the formation of single layer clusters whose size increases with the amount of Fe. The structure of the stable pseudomorphic fcc clusters was studied using scanning tunnelling microscopy. The clusters were grown and measured in-situ by x-ray magnetic circular dichroism of Fe L@sub 2,3@ edge at beamline ID8 of the European Synchrotron Radiation Facility in Grenoble. Sum rule analysis was used to extract the magnetic spin and orbital moments with changing cluster size. The clusters show superparamagnetic behaviour with blocking temperature in the range 10-250 K increasing with cluster size. The easy axis of magnetization is perpendicular to the surface for all the range of cluster sizes studied. The orbital moment of the clusters as well as its angular anisotropy (related to the magnetic anisotropy energy) is enhanced in comparison with the bulk value and increases with decreasing cluster size. This enhancement is given by the increase in the number of perimeter atoms as the cluster radius diminishes. The perimeter atoms have reduced atomic coordination leading to the higher orbital moment. The magnetic spin moment per atom is lower than for bulk Fe. This behaviour can be explained by changes in the local atomic structure that is very sensitive to the atomic volume.