VANADIUM - FROM CLUSTER TO SEMIINFINITE CRYSTAL

Antiferromagnetic coupling between nearest neighbor vanadium atoms is discussed in the case of free-standing cluster and slabs, steps at the surface of V and V islands on Ag(001). In the self-consistent tight-b inding derivation of the unrestricted approximation of the Hubbard-Ham iltonian, we have investigated the onset of magnetism in terms of the exchange integral J. For each topological arrangement of the V cluster s [free-standing or as overlayer on Ag(001)], various possible magneti c states are considered and transition from nonmagnetic to magnetic or der is characterized. The (001) surface is shown to present magnetism for a value of J lower than those for the other crystallographic faces .