Intrinsic orbital and spin magnetic moments of quasifree Rh clusters on inert xenon buffer layers are measured using x-ray magnetic circular dichroism. The moments strongly vary as a function of average cluster size. A maximum total moment of 0.4 B per atom and large orbital-to-spin moment ratios up to 60% appear for Rh N clusters with average size N = 20, suggesting that cluster geometries are biplanar. The magnetism is further studied between two extreme limits, from quasifree few-atom-sized clusters situated on a xenon layer toward Rh nanostructures in contact with a weakly interacting Ag͑100͒ substrate. Density-functional theory calculations for different cluster sizes and Rh-Ag coordination explain the unexpected quenching of Rh moments in the case of directly deposited Rh on Ag͑100͒ reported by Honolka et al. ͓Phys. Rev. B 76, 144412 ͑2007͔͒.
The magnetic behavior of cobalt nanocluster arrays arranged on a boron-nitride nanomesh and capped with MnPt layers of varying thickness θMnPt is investigated. The magnetic properties of the arrays are found to be strongly dependent on the cobalt nanocluster size: large 3-dimensional clusters of several nanometers size under the influence of only θMnPt∼5 nm exhibit prototypical exchange bias behavior, whereas small 2-dimensional clusters of about 1 nm in diameter show superparamagnetic behavior, however, with a strong quenching of the average cobalt magnetization. The latter effect is correlated with the formation of a stable antiferromagnetic phase at increasing θMnPt and is discussed in terms of the domain state exchange bias model. The quenching suggests either partial antiferromagnetic alignment of cobalt spins within a cluster or a random orientation of cobalt cluster macrospins with respect to each other.
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