EXAFS study of Co growth on Pt(9 9 7): from atomic chains to two monolayers

The magnetism of atomic chains and layers is sensitive to tiny changes in the crystallographic structure and in the lattice parameters of few hundredth of Å. EXAFS is known to be sensitive to such small changes. Here we present an EXAFS study of Co chains and layers grown on a stepped Pt(9 9 7) surface. As a result, we see that the misfit between Co and Pt is too high to permit a perfect pseudomorphic epitaxial growth of cobalt, even for 0.25 ML (a coverage where Co forms wires of 2 monoatomic width). The in-plane interatomic distance between Co atoms varies from 2.66 Å for 0.25 ML to 2.56 Å for 2 ML. We find no in-plane crystallographic anisotropy and the width of the radial distribution around Co atoms function is very large.