On the anomalous temperature dependence of the magnetic moment of cobalt clusters

Cluster beam experiments using Stern-Gerlach type measurements yield information about the magnetic properties of transition metal clusters. One of the intriguing results to have come out of such measurements is the observation of a magnetic moment in cobalt clusters that increases with temperature up to about 500 K, before decreasing as the bulk Curie temperature is approached. We argue in this paper that this behaviour can be understood as an artifact of the method of extracting results from raw experimental data, and that the origin of the anomalous behaviour lies in the neglect of the magnetic anisotropy in the analysis.