Spin configuration of Gd-13 clusters

The structure and spin configuration of a Gd-13 cluster has been examined using theoretical electronic structure calculations and a Heisenberg model. The structure calculations show that the ground state geometry of the cluster has an hcp arrangement with a slightly reduced nearest-neighbor distance compared to bulk and an average moment of 7.8 mu B/atom. The Heisenberg model is calculated using an RKKY-like interaction. The effects of competing ferromagnetic and antiferromagnetic coupling for the nearest- and next-nearest-neighbor interaction, respectively, is investigated. It is shown that for a range of interaction strengths the spins assume a canted configuration. This effect leads to lower net magnetization of the cluster, and accounts for the anomalous low moments of Gd-n clusters which have been experimentally observed.