Ferromagnetic nanostructures of oxygen on Ag(111)

First principles calculations were performed to investigate the robustness of oxygen adsorbed structures that show ferromagnetic properties. These ferromagnetic properties are induced by ferromagnetic superexchange interactions and Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions. Such ferromagnetic oxygen adsorbed structures appear only in the case of coverages higher than 0.5 ML, because the ferromagnetic superexchange interactions and RKKY interactions are appreciable between O-O only for short distances. In this work, we focused on single oxygen atom diffusion parallel and perpendicular to Ag(111) surfaces. The in-plane diffusion could induce associative desorption, which reduces the oxygen coverage. On the other hand, diffusion to the subsurface could quench the magnetic moment. These diffusion paths have effective diffusion barriers of 0.78 eV. Thus, such diffusion rarely occurs in low temperature regions