Gold deposited on the ${\mathrm{Fe}}_3{\mathrm{O}}_4(001)$ surface at room temperature was studied using scanning tunneling microscopy (STM) and x-ray photoelectron spectroscopy (XPS). This surface forms a $(\sqrt{2}\times \sqrt{2})R45°$ reconstruction, where pairs of Fe and neighboring O ions are slightly displaced laterally producing undulating rows with “narrow” and “wide” hollow sites. At low coverages, single Au adatoms adsorb exclusively at the narrow sites, with no significant sintering up to annealing temperatures of $400°\mathrm{C}$. We propose the strong site preference to be related to charge and orbital ordering within the first subsurface layer of ${\mathrm{Fe}}_3{\mathrm{O}}_4(001)\mathrm{\text{−}}(\sqrt{2}\times \sqrt{2})R45°$. Because of its high thermal stability, this could prove an ideal model system for probing the chemical reactivity of single atomic species.

• Received 26 March 2012

DOI:https://doi.org/10.1103/PhysRevLett.108.216103