Magnetic properties of small Yttrium clusters

The magnetic properties of small Y-N clusters are studied by using a tight- binding Hubbard Hamiltonian in the unrestricted Hartree-Fock approximation. Several types of cluster geometries are considered in order to see the eff ects of the size and symmetry of the structures on the magnetic properties. The average magnetic moments [M] are found to be constant over large domai ns of variations in the interatomic distance, a fact that can be explained by the existing closed shell electronic configurations at least for one spi n direction in all our magnetic solutions. Small energy gains upon the onse t of magnetization are obtained, which reveals the low stability of the mag netic solutions. Our results contradict the prediction of a magnetic-nonmag netic transition at a large cluster size (about 90 atoms) for these kinds o f systems.