Régis Decker

Helmholtz-Zentrum Berlin für Materialien und Energie

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Harald Brune

École Polytechnique Fédérale de Lausanne

Svetlana Klyatskaya

Karlsruhe Institute of Technology

Uta Schlickum

Technische Universität Braunschweig

Mario Ruben

Centre National de la Recherche Scientifique

Johannes V. Barth

Technical University of Munich

Florian Klappenberger

Donostia International Physics Center

Kari Ruotsalainen

Helmholtz-Zentrum Berlin für Materialien und Energie

Alexander Föhlisch

Helmholtz-Zentrum Berlin für Materialien und Energie

Annette Pietzsch

Helmholtz-Zentrum Berlin für Materialien und Energie

R. Wiesendanger

Universität Hamburg

Cooperative Institutions

Helmholtz-Zentrum Berlin für Materialien und Energie

University of California, Berkeley

Centre National de la Recherche Scientifique

Technical University of Munich

Lawrence Berkeley National Laboratory

École Polytechnique Fédérale de Lausanne

Universität Hamburg

Karlsruhe Institute of Technology

Donostia International Physics Center

University of Potsdam

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Atomic-scale magnetism of cobalt-intercalated graphene

Physical Review B (2013)

Régis Decker Jens Brede Nicolae Atodiresei Vasile Caciuc Stefan Blügel

Using spin-polarized scanning tunneling microscopy and density functional theory, we have studied the structural and magnetic properties of cobalt-intercalated graphene on Ir(111). The cobalt forms monolayer islands being pseudomorphic with the Ir(111) beneath the graphene. The strong bonding between graphene and cobalt leads to a high corrugation within the Moir\'e pattern which arises due to the lattice mismatch between the graphene and the Co on Ir(111). The intercalation regions exhibit an out-of-plane easy axis with an extremely high switching field, which surpasses the significant values reported for uncovered cobalt islands on Ir(111). Within the Moir\'e unit cell of the intercalation regions, we observe a site-dependent variation of the local effective spin polarization. State-of-the-art first-principles calculations show that the origin of this variation is a site-dependent magnetization of the graphene: At top sites the graphene is coupled ferromagnetically to the cobalt underneath, while it is antiferromagnetically coupled at fcc and hcp sites.

Magnetism

Atomic units

10.1103/physrevb.87.041403

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Citations (148)

Scanning Tunneling Microscopy of Graphene on a Boron Nitride Substrate

Bulletin of the American Physical Society (2011)

Yang Wang Régis Decker Victor W. Brar William Regan Hsin‐Zon Tsai

Source

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Local tunnel magnetoresistance of an iron intercalated graphene-based heterostructure

Journal of Physics Condensed Matter (2014)

Régis Decker Maciej Bazarnik Nicolae Atodiresei Vasile Caciuc Stefan Blügel

The lateral variation of the tunnel magnetoresistance (TMR) of a graphene-based vertical heterostructure is studied by spin-polarized scanning tunneling microscopy (SP–STM) using an Fe-coated probe tip. The well-defined heterostructure is obtained by the intercalation of a magnetic Fe monolayer at the graphene/Ir(1 1 1) interface. Its structure is characterized by a moiré pattern with a high corrugation. In contrast to the Fe / Ir(1 1 1) surface, graphene/Fe / Ir(1 1 1) exhibits ferromagnetic order with an out-of-plane easy magnetization axis. At the nanometer scale, our experiments reveal that the moiré pattern induces a lateral variation of the TMR, which reaches 80%. The measured TMR at valleys of the moiré pattern is higher than at hills. We interpret this modulation in terms of a different hybridization between graphene and Fe at valleys and hills due to a different graphene–Fe distance at these sites, which leads to a different transmission of spin-polarized states.

10.1088/0953-8984/26/39/394004

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Citations (23)

Surface Chemistry: Surface-Confined Self-Assembly of Di-carbonitrile Polyphenyls (Adv. Funct. Mater. 7/2011)

Advanced Functional Materials (2011)

Svetlana Klyatskaya Florian Klappenberger Uta Schlickum Dirk Kühne Matthias Marschall

This Feature Article reports on the controlled formation and structure-functionality aspects of vacuum-deposited self-assembled organic and metal-organic networks at metal surfaces using ditopic linear and nonlinear molecular bricks, namely di-carbonitrile polyphenyls. Surface confined supramolecular organization of linear aromatic molecules leads to a fascinating variety of open networks. Moreover, cobalt-directed assembly of the same linear linkers reveals highly regular, open honeycomb networks with tunable pore sizes representing versatile templates for the organization of molecular guests or metal clusters and the control of supramolecular dynamers. In addition, the 2D nanopore organic networks act as arrays of quantum corrals exhibiting confinement of the surface-electronic states of the metallic substrate. A reduction of the linker symmetry leads to the formation of disordered, glassy coordination networks, which represent a structural model for amorphous materials.

Linker

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Nanopore

10.1002/adfm.201190019

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Gate-controlled ionization and screening of cobalt adatoms on a graphene surface

Nature Physics (2010)

Victor W. Brar Régis Decker Hans-Michael Solowan Yang Wang Lorenzo Maserati

10.1038/nphys1807

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Citations (261)

High-Quality 2D Metal−Organic Coordination Network Providing Giant Cavities within Mesoscale Domains

Journal of the American Chemical Society (2009)

Dirk Kühne Florian Klappenberger Régis Decker Uta Schlickum Harald Brune

A surface-supported open metal-organic nanomesh featuring a 24 nm(2) cavity size and extending to mum domains was fabricated by Co-directed assembly of para-hexaphenyl-dicarbonitrile linker molecules in two dimensions. The metallosupramolecular lattice is thermally robust and resides fully commensurate on the employed Ag(111) substrate as directly verified by high-resolution scanning tunneling microscopy observations.

Nanomesh

Linker

Lattice (music)

Coronene

10.1021/ja809946z

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Citations (142)

Metal−Organic Honeycomb Nanomeshes with Tunable Cavity Size

Nano Letters (2007)

Uta Schlickum Régis Decker Florian Klappenberger Giorgio Zoppellaro Svetlana Klyatskaya

We present a systematic study of metal−organic honeycomb lattices assembled from simple ditopic molecular bricks and Co atoms on Ag(111). This approach enables us to fabricate size- and shape-controlled open nanomeshes with pore dimensions up to 5.7 nm. The networks are thermally robust while extending over μm2 large areas as single domains. They are shape resistant in the presence of further deposited materials and represent templates to organize guest species and realize molecular rotary systems.

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Honeycomb

10.1021/nl072466m

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Citations (308)

Using metal-organic templates to steer the growth of Fe and Co nanoclusters

Applied Physics Letters (2008)

Régis Decker Uta Schlickum Florian Klappenberger Giorgio Zoppellaro Svetlana Klyatskaya

Regularly sized Fe and Co nanostructures are created using two-dimensional metal-organic honeycomb lattices as templates. They consist of dicarbonitrile-polyphenyl molecules coordinated to Co centers on Ag(111). Subsequently deposited Fe or Co atoms nucleate clusters at specific sites on top of the metal-organic lattices while leaving their hexagonal pores empty. Choosing the deposition temperature, one can selectively decorate the molecules (120K) or the Co coordination nodes (190K) with Fe. The distance between the Fe and Co clusters and their shape can be adjusted through the lattice constant of the template by varying the number of phenyl rings in the molecules.

Nanoclusters

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Lattice constant

Lattice (music)

Organic molecules

10.1063/1.3040328

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Citations (47)

Thresholding of the Elliott-Yafet spin-flip scattering in multi-sublattice magnets by the respective exchange energies

Scientific Reports (2021)

Artur Born Régis Decker Robby Büchner Robert Haverkamp Kari Ruotsalainen

How different microscopic mechanisms of ultrafast spin dynamics coexist and interplay is not only relevant for the development of spintronics but also for the thorough description of physical systems out-of-equilibrium. In pure crystalline ferromagnets, one of the main microscopic mechanism of spin relaxation is the electron-phonon (el-ph) driven spin-flip, or Elliott-Yafet, scattering. Unexpectedly, recent experiments with ferro- and ferrimagnetic alloys have shown different dynamics for the different sublattices. These distinct sublattice dynamics are contradictory to the Elliott-Yafet scenario. In order to rationalize this discrepancy, it has been proposed that the intra- and intersublattice exchange interaction energies must be considered in the microscopic demagnetization mechanism, too. Here, using a temperature-dependent x-ray emission spectroscopy (XES) method, we address experimentally the element specific el-ph angular momentum transfer rates, responsible for the spin-flips in the respective (sub)lattices of Fe[Formula: see text]Ni[Formula: see text], Fe[Formula: see text]Ni[Formula: see text] and pure nickel single crystals. We establish how the deduced rate evolution with the temperature is linked to the exchange coupling constants reported for different alloy stoichiometries and how sublattice exchange energies threshold the related el-ph spin-flip channels. Thus, these results evidence that the Elliott-Yafet spin-flip scattering, thresholded by sublattice exchange energies, is the relevant microscopic process to describe sublattice dynamics in alloys and elemental magnetic systems.

Ferrimagnetism

10.1038/s41598-021-81177-9

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Citations (5)

Orbital-overlap-driven hybridization in 3d-transition metal perovskite oxides LaMO3 (M = Ti-Ni) and La2CuO4

Communications Physics (2024)

Chun-Yu Liu Lorenzo Celiberti Régis Decker Kari Ruotsalainen Katarzyna Siewierska

Abstract The wide tunability of strongly correlated transition metal (TM) oxides stems from their complex electronic properties and the coupled degrees of freedom. Among the perovskite oxides family, LaMO 3 (M = Ti-Ni) allows an M-dependent systematic study of the electronic structure within the same-structure-family motif. While most of the studies have been focusing on the 3d TMs and oxygen sites, the role of the rare-earth site has been far less explored. In this work, we use resonant inelastic X-ray scattering (RIXS) at the lanthanum N 4,5 edges and density functional theory (DFT) to investigate the hybridization mechanisms in LaMO 3 . We link the spatial-overlap-driven hybridization to energetic-overlap-driven hybridization by comparing the RIXS chemical shifts and the DFT band widths. The scope is extended to highly covalent Ruddlesden-Popper perovskite La 2 CuO 4 by intercalating lanthanum atoms to rock-salt layers. Our work evidences an observable contribution of localized lanthanum 5p and 4f orbitals in the band structure.

10.1038/s42005-024-01642-5

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Citations (5)