Magnetic properties of 4d transition-metal clusters

We analyze the stability of magnetic states obtained within the tight-binding model solved by molecular dynamics for cube-octahedral (fee) and icosahedral clusters of 3d (Ni and Co) and 4d (Pd, Rh, and Ru) transition metals. The magnetic states are stabilized by the Hund's rule exchange interaction between the d orbitals. Taking realistic parameters deduced from band structure calculations and spectroscopic data, we obtained saturated ferromagnetism for Ni-13, Co-13, and Pd-13 clusters, while Rh-13 fcc and Ru-13 clusters are partially magnetic, with an antiferromagnetic orientation of the moments on the central atoms in Ru clusters. Our results for 4d transition-metal clusters agree qualitatively with the recent experimental data and with other calculations. Metastable magnetic clusters were identified in several situations. We found a dependence of the equilibrium lattice constant on the magnetization in the considered clusters which may be explained by the character of wave functions in the cluster electronic structure.