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The spin and orbital configuration of magnetic metal phthalocyanines (MPcs) deposited on metallic substrates are strongly influenced by the rehybridization of the molecular states with the underlying metal. FePc, CoPc, and CuPc isolated molecules are archetypal systems to investigate the interrelationship between magnetic moments and orbital symmetry after deposition on a metallic substrate. MPcs form long-range ordered chains self-assembled along the reconstructed channels of the Au(110) surface. X-ray magnetic circular dichroism from the L-2,L-3 absorption edges of Fe, Co, and Cu shows that the orbital and spin configuration are strongly modified upon adsorption on the Au(110) surface if the orbitals responsible of the magnetic moment are involved in the interaction process. The magnetic moment for a single layer of molecular chains is completely quenched for the CoPc molecules, fully preserved for the CuPc and reduced for the FePc ones. The modified magnetic configuration is confined to the very interface layer, i.e., to the MPc molecules bound to the metal substrate up to the compact packing of the single layer. The different response can be rationalized in terms of the symmetry/orientation of the metal-ion d states interacting with the substrate states, as indicated by density functional theory calculations in agreement with experimental findings. DOI: 10.1103/PhysRevB.87.16540

We investigate the electronic structure of Ca1−xSrxVO3 using photoemission spectroscopy. Core level spectra establish an electronic phase separation at the surface, leading to distinctly different surface electronic structure compared to the bulk. Analysis of the photoemission spectra of this system allowed us to separate the surface and bulk contributions. These results help us to understand properties related to two vastly differing energy-scales, namely the low energy-scale of thermal excitations (∼ kBT ) and the high-energy scale related to Coulomb and other electronic interactions.PACS numbers 71.30.+h, 71.27.+a, 73.20.At, 79.60.Bm The electronic structure of strongly correlated transition metal oxides has attracted a great deal of attention both theoretically [1] and experimentally [2] due to many exotic properties exhibited by these systems such as high temperature superconductivity and colossal magnetoresistance. In order to investigate such issues, photoemission spectroscopy has been extensively employed due to its ability to probe the electronic structure directly. While this technique is highly surface sensitive as observed in rare earth intermetallics [3], its extensive use to understand the bulk properties of transition metal (TM) oxides [4] is based on the implicit assumption of very similar electronic structures at the surface and in the bulk. We observe a spectacular failure of this assumption in Ca 1−x Sr x VO 3 .Ca 1−x Sr x VO 3 is a solid solution of CaVO 3 and SrVO 3 where the bandwidth W can be systematically controlled due to a buckling of the V-O-V bond angle from ∼ 180• in SrVO 3 to ∼ 160. Thus, Ca 1−x Sr x VO 3 is ideally suited for the systematic study of the competition between local interactions and itineracy, which leads to several strong correlation effects. This system is arguably the simplest strongly correlated transition metal oxide, since it remains paramagnetic down to the lowest temperature measured so far (T = 50 mK), has typical Fermi liquid behavior and has nominally just one conduction electron per site of V 4+ . Despite these facts, important aspects of its fundamental physics remain unclear, particularly in terms of its contrasting high-energy spectroscopic and low-energy thermodynamic properties [1,6]. The spectroscopic properties and the thermodynamic properties belong to vastly different energy scales: the former corresponds to a high energy (typically 10 ∼ 10 3 eV) perturbation to the system, while the latter probes electrons typically within k B T (∼ 1 meV) of E F . There is indeed a-priori no reason to believe that the same model physics will be valid in both the regimes.In this study, we observe a strong dependence of the photoemission spectra from Ca 1−x Sr x VO 3 with the escape depth λ of the photoelectrons, siginifying very different surface and bulk electronic structures. The core level spectra exhibit an electronic phase separation at the surface, possibly due to an enhanced correlation effect and leading to a distinctly different surface electronic stru...

Understanding the adsorption mechanisms of large molecules on metal surfaces is a demanding task. Theoretical predictions are difficult because of the large number of atoms that have to be considered in the calculations, and experiments aiming to solve the molecule-substrate interaction geometry are almost impossible with standard laboratory techniques. Here, we show that the adsorption of complex organic molecules can induce perfectly ordered nanostructuring of metal surfaces. We use surface X-ray diffraction to investigate in detail the bonding geometry of C(60) with the Pt(111) surface, and to elucidate the interaction mechanism leading to the restructuring of the Pt(111) surface. The chemical interaction between one monolayer of C(60) molecules and the clean Pt(111) surface results in the formation of an ordered sqrt[13] x sqrt[13]R13.9 degrees reconstruction based on the creation of a surface vacancy lattice. The C(60) molecules are located on top of the vacancies, and 12 covalent bonds are formed between the carbon atoms and the 6 platinum surface atoms around the vacancies. In-plane displacements induced on the platinum substrate are of the order of a few picometres in the top layer, and are undetectable in the deeper layers.

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