Magnetism in clusters of non-magnetic elements: Pd, Rh, and Ru

Abstract.

We have carried out ab initio calculations on clusters of Pd with 2-23, 55, and 147 atoms using ultrasoft pseudopotential plane wave method and spin-polarized generalized gradient approximation for the exchange-correlation energy. It is found that these clusters have an icosahedral growth and size dependent oscillatory magnetic moments. Atomically closed shell 13, 55, and 147 atom clusters have large moments of 8, 26, and 60 μ _B, respectively. But cubic Pd₅₅ has a small moment of 10 μ _B only. This shows the importance of the icosahedral structure in the development of magnetism in Pd clusters. The magnetic energy is, however, small and the moments get quenched by H adsorption. Similar studies have been carried out on Rh and Ru clusters. In the atom these have large moments as compared to zero for Pd and therefore, the moments on clusters are also large. However, the moments decrease rapidly as the size grows.