Spatial Dependence of Kondo Screening and Magnetic Anisotropy on Saturated Copper Nitride Islands

Co adatoms on a copper nitride surface constitute a unique system for studying the interplay between Kondo physics and anisotropy in a high spin atom (S=3/2). By using scanning tunneling spectroscopy techniques, we can determine both the energy scales of the Kondo screening and the spin excitations on a single atom. Here we study the case of Co adatoms on large nitride islands that form as the copper surface is saturated with nitrogen. These islands present a rich spatial variation of their electronic structure. We observe how changes in the electronic structure of the insulator result in dramatic changes in the spectroscopy of the cobalt adatoms: a considerable increase of the anisotropy energy occurs as the Kondo resonance disappears. These results allow us to explore in detail the interplay between these two phenomena.