Oscillatory magnetic coupling in cobalt/copper epitaxial layers: The surface science approach

Some examples of the impact of surface-sensitive techniques on our understanding of oscillatory magnetic coupling are discussed. STM shows that Co grows on Cu(111) as triangular islands of bilayer height that do not coalesce upon further deposition. The resulting film, although epitaxial and single crystalline is actually granular. The visualized twinned fcc crystallites and their associated grain boundaries may be the subtle structural imperfection obscuring antiferromagnetic coupling in Co/Cu(111) superlattices grown in ultra high vacuum. On Cu(100), where the oscillatory coupling has been reproduced by many groups, new LEED and EXAFS data prove that the Co layers present a tetragonally distorted fcc structure and quantify the lattice parameters of the different layers.