Magnetism of Fe-Co nanostructures on flat and stepped W(110) surfaces:: Effects of dimensionality and substrate -: art. no. 014430

We present an ab initio local-spin-density investigation of the magnetism in nanostructures (ultrathin films, stripes, wires) of Fe, Co, and Fe-Co alloys on flat and stepped W(110) surfaces. Particular attention is devoted to the influence of the reduced dimensionality and of adsorbate-substrate hybridization on the magnetic properties. In pseudomorphic Fe-Co films on flat W(110) interface, hybridization is shown to strongly reduce the tendency towards ferromagnetic ordering with increasing Co content. Reconstructed close-packed Co films remain ferromagnetic. In biatomic Fe-Co stripes on W(970) surface, hybridization effects enhanced by relaxation lead to a rapid decrease of the magnetic energy differences with Co concentration. Monoatomic Fe-Co wires are predicted to order antiferromagnetically at all compositions. We demonstrate that antiferromagnetism results from the combined influence of the reduced dimensionality, the strain in the wires, and of the hybridization with the substrate.