ATOMIC-SCALE OBSERVATIONS OF ALLOYING AT THE CR-FE(001) INTERFACE

While much progress has been made using epitaxial growth of Fe/Cr/Fe s tructures to study magnetic exchange coupling, a number of anomalies h ave arisen in studies of this model system. Using scanning tunneling m icroscopy and spectroscopy to investigate Cr growth on Fe(001), we hav e identified a potential structural cause of these anomalies. We show that Cr growth under layer-by-layer conditions on Fe(001) leads to the formation of a Cr-Fe alloy. We exploit a Cr and Fe surface state to i dentify single Cr impurities in Fe and evaluate the alloy concentratio ns with increasing Cr coverage.