We report on the magnetic properties of individual Fe atoms deposited on MgO(100) thin films probed by x-ray magnetic circular dichroism and scanning tunneling spectroscopy. We show that the Fe atoms have strong perpendicular magnetic anisotropy with a zero-field splitting of 14.0 AE 0.3 meV=atom. This is a factor of 10 larger than the interface anisotropy of epitaxial Fe layers on MgO and the largest value reported for Fe atoms adsorbed on surfaces. The interplay between the ligand field at the O adsorption sites and spin-orbit coupling is analyzed by density functional theory and multiplet calculations, providing a comprehensive model of the magnetic properties of Fe atoms in a low-symmetry bonding environment.

We report on the self-assembly of Fe adatoms on a Cu(111) surface that is patterned by a metal-organic honeycomb network, formed by coordination of dicarbonitrile pentaphenyl molecules with Cu adatoms. Fe atoms landing on the metal surface are mobile and steered by the quantum confinement of the surface state electrons towards the center of the network hexagonal cavities. In cavities hosting more than one Fe, preferential interatomic distances are observed. The adatoms in each hexagon aggregate into a single cluster upon gentle annealing. These clusters are again centered in the cavities and their size is discerned by their distinct apparent heights. Self-assembly of adatoms or small clusters at surfaces enables the bottom-up fabrication of well-defined nanoscale structures. Well ordered nanostructure superlattices can be created by the nucleation and growth on template surfaces exhibiting long period adatom binding energy variations, such as equidistant pinning sites [1] or networks of repulsive line defects [2]. Besides surface reconstructions and stress relief patterns of epitaxial thin films, nanoporous metalorganic networks [3,4] are potential candidates for such templates. So far, deposition of metal atoms on the latter systems resulted in the decoration of the organic molecules themselves or of the coordination nodes, but not in equidistant clusters on the substrate [5].An additional source of order can be introduced by the quasi-two-dimensional (2D) electron gas of a surface state mediating long-range adsorbate interactions [6][7][8]. On homogeneous surfaces, they stabilize atomic superlattices [6][7][8][9]. Surface state confinement by static scatterers results in local density of state (LDOS) patterns that influence the adsorbate binding energy. In 1D structures formed by substrate steps or strings of atoms or molecules, this leads to 1D confinement of adsorbed atoms [10][11][12][13]. The surface state LDOS patterns formed in a network of hexagonal molecular cavities have been demonstrated to influence the binding sites of adsorbed CO molecules [14].Here, we demonstrate strong surface state confinement by a metal-organic network, preferred adatom locations due to the LDOS pattern created in each cavity, and aggregation of these atoms to a single cluster per network cavity, thus giving rise to a cluster superlattice with the period of the metal-organic template. Our system is a honeycomb network with % 5 nm period formed by dicarbonitrile pentaphenyl (NCÀPh 5 ÀCN) molecules and Cu atoms on Cu(111), and the steered adatoms are Fe.The Cu(111) substrate has been prepared by Ar þ sputter and annealing cycles. The NCÀPh 5 ÀCN molecules [3] were evaporated from a molecular effusion cell at 230 C.

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We present the results of temperature-dependent self-assembly of dicarbonitrile-pentaphenyl molecules (NC-Ph 5 -CN) on Cu(111). Our low-temperature scanning tunneling microscopy study reveals the formation of metal-organic and purely organic structures, depending on the substrate temperature during deposition (160-300 K), which determines the availability of Cu adatoms at the surface. We use tip functionalization with CO to obtain submolecular resolution and image the coordination atoms, enabling unequivocal identification of metal-coordinated nodes and purely organic ones. Moreover, we discuss the somewhat surprising structure obtained for deposition and measurement at 300 K. C 2015 AIP Publishing LLC. [http://dx

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