From monoatomic multilayers to ordered alloys

Recent progress in UHV preparation and characterization methods resulted in a large variety of novel materials. Among them, magnetic multilayers have become one of the mostly investigated system due to interesting phenomena like oscillating indirect exchange coupling, spin dependent electron transport, or large perpendicular anisotropies. An attractive possibility given by the molecular beam epitaxy is to grow the multilayer structures on atomic scale by the so-called atomic layer deposition. At the low thickness limit, a multilayer structure, in which few atomic layers of different metals are stacked alternately, is expected to be an artificial ordered alloy. Such artificial material, which does not exist in the equilibrium bulk phase, was constructed for the first time as the AuFe ordered alloy of the L1(0) structure. Our conversion electron Mossbauer spectroscopy studies of this system verified the existence of the tetragonal phase, which is responsible for the perpendicular anisotropy. The ordering process is influenced by the complicated growth of Fe on Au, as shown by the atomic scale scanning tunneling microscopy investigations. Other systems to be presented are FeAl (strong ordering mechanism in the bulk) and FeCr (miscible in the wide concentration range) monoatomic superlattices.