Magnetism of exposed and Co-capped Fe nanoparticles

Abstract The effect of capping a dilute assembly of nanoscale mass-selected Fe clusters with a Co thin film has been studied using X-ray magnetic circular dichroism (XMCD). The clusters, containing around 400 atoms, were deposited in situ from a gas-aggregation source onto highly oriented pyrolytic graphite. The exposed clusters possess magnetic moments that are enhanced compared to the bulk, by around 4% for m spin and around 75% for m orb . In addition, a surface core level shifted component is observed in the L 3,2 XMCD spectrum. Upon adding the Co layer, the surface component disappears, m orb is decreased for the Fe clusters, and m spin increases. The exposed clusters are magnetically isotropic but a strong in-plane anisotropy is observed after depositing the Co overlayer. We attribute this to the shape of the Co islands in which the Fe clusters are embedded.