Interplay between structural, magnetic, and electronic properties in aFeO∕Pt(111)ultrathin film

Abstract

We have investigated the magnetic and electronic properties of a FeO film grown on Pt(111).Coupling first principle GGA+U calculations with STM measurements we have identified the principal mechanisms for the structural and electronic non-homogeneous characteristics observed in the Moiré unit cell formed between oxide film and metal support. We show that both free and supported FeO(111) monolayers present an anti-parallel alignment of the magnetic moments and that the modulation of structural and electronic film properties is driven by the local strength of the interaction between the film and the substrate. Namely, due to the lattice mismatch between Pt (111) and the FeO film, the interface properties are different in different regions of the supercell. In particular, for the Fe-top site, where this interaction is weak, the resulting small layer rumpling and large interface separation give origin to a peculiar behavior of the work function, coherent with the most recent experimental findings. In what concerns fine structural and electronic characteristics, in particular the modulation of the work function and the site assignment in the STM images, our results show that a good agreement with the experimental interpretations can be obtained only within more robust, non-pseudomorphic computational models.

Identification of the electronic structure differences between polar isostructural FeO and CoO films by core-level soft x-ray spectroscopy

“…Both TM monoxide films are single TM-O bilayer-thick and oxygen terminated, the metal atoms decorate the interface layer with the same periodicity. The findings of earlier photoelectron diffraction (PD) 18 , low energy electron diffraction (LEED), and scanning tunneling microscopy (STM) 19 studies mostly agree with the recent ones 20 , that the FeO films grown on Pt(111) have a lattice mismatch which is revealed as a superstructure (Moiré patterns). X-ray photoelectron spectroscopy (XPS) studies show that the oxidation state of Fe is 2+; indicating the formal charges are close to the charges in FeO stoichiometry 21,22 .…”

“…Interfacial metal atoms can be found on three-fold fcc, hcp, and top sites of Pt (111) surface and their effects are translated into Moiré superstructure observed on these films 33 . It has been shown by STM studies that the surface potential of FeO films becomes modulated due to corrugation of the Moiré superstructures 20,34 . Despite the lack of information that quantifies the variation of the surface potential of CoO films, a similar behavior is expected.…”

Water clustering on nanostructured iron oxide films

“…We used the DFT þ U approach by Dudarev et al 59 to correct the on-site Coulomb interaction between Fe 3d orbitals. As in previous DFT studies of the FeO/Pt(111) system 30,60,61 we used the projector augmented wave method 62,63 and chose the parameters describing the on-site Coulomb interaction between Fe 3d orbitals as U eff ¼ U-J ¼ 3 eV. To model the 1 ML FeO/Pt(111) surface we used the experimentally observed (O91 Â O91)R5.2°unit cell consisting of one layer of Fe atoms and one layer of O atoms supported on a three-layer Pt(111) slab.…”

Iron oxide surfaces

“…However, it would be remiss not to at least mention a few highlights of the recent literature. Giordano et al [372] have shown that the properties of the thin film are strongly influenced by the coupling to the metal substrate, and that properties such as the work function vary across the resulting Moiré structure. Au and Pd adatoms become charged by electrons that tunnel through the oxide [386; 387].…”