Magnetism of exposed and Co-capped Fe nanoparticles

• 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-plans 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.

Nyckelord

nanoscale magnetism

ray circular-dichroism

sum-rules

clusters

cobalt

moments

iron

magnetization

dependence

films

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