SPIN-POLARIZED ELECTRONIC-STRUCTURE OF VANADIUM

We perform a systematical study of V slabs from one to five planes. Various configurations are considered: ferromagnetic, layered-antiferromagnetic, and in-plane ferromagnetic. The local magnetic moments are deduced, within a Hubbard Hamiltonian, versus the exchange integral J and the lattice parameter. In bulk vanadium, antiferromagnetic structures occur more readily, i.e., at smaller J values than the ferromagnetic structures. In free-standing slabs, the onset of magnetism is obtained for a J value much smaller than in the bulk. In the monolayer, a competition between the in-plane antiferromagnetism and ferromagnetism is present, but a total-energy calculation versus the lattice parameter indicates the stabilization of the paramagnetic state. For thicker slabs, layered antiferromagnetic structures are present for the bulk lattice parameter in the cases of (001) and (111) crystallographic faces; for the (011) face, however, only in-plane antiferromagnetism is present. The magnetism of vanadium epitaxially grown on Ag(001) exhibits in-plane antiferromagnetism for one monolayer, but layered antiferromagnetic structures instead for thicker slabs. In all the cases investigated, antiferromagnetic structures occur for J values smaller than those for ferromagnetic structures.