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Cojocariu I, Perilli D, Feyer V, Jugovac M. Graphene-Molecule Hybridization at a Ferromagnetic Interface. Chemistry 2024; 30:e202400857. [PMID: 38842468 DOI: 10.1002/chem.202400857] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2024] [Revised: 06/04/2024] [Accepted: 06/05/2024] [Indexed: 06/07/2024]
Abstract
The introduction of a graphene (Gr) buffer layer between a ferromagnetic substrate and a metallorganic molecule is known to mediate the magnetic coupling between them, an effect attributed to a weak hybridization between graphene and molecule. In this paper, we present experimental evidence of this effect through a detailed investigation of the frontier electronic properties of iron phthalocyanine deposited on cobalt-supported graphene. Despite being physisorbed, the molecular adsorption on Gr/Co induces a sizeable charge transfer from graphene to the molecular macrocycle leading to the partial occupation of the LUMO and the appearance of an energetically localized hybrid state, which can be attributed to the overlap between the graphene pz state and the molecular macrocycle. Graphene is not inert either; the adsorption of the molecule induces doping and alters the Fermi velocity of both the hybrid minicone state and the Dirac cone. Similar effects are observed when the molecular periphery is decorated with fluorine atoms, known for their electron-withdrawing properties, with minimal changes in the energy alignment.
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Affiliation(s)
- Iulia Cojocariu
- Dipartimento di Fisica, Università degli Studi di Trieste, Via A. Valerio 2, 34127, Trieste, Italy
- Elettra - Sincrotrone Trieste S.C.p.A, Basovizza S.S. 14, Km 163.5, 34149, Trieste, Italy
| | - Daniele Perilli
- Dipartimento di Scienza dei Materiali, Università degli Studi di Milano-Bicocca, via R. Cozzi 55, 20125, Milano, Italy
| | - Vitaliy Feyer
- Peter Grünberg Institute (PGI-6), Forschungszentrum Jülich, Wilhelm-Johnen-Straße, 52428, Jülich, Germany
| | - Matteo Jugovac
- Elettra - Sincrotrone Trieste S.C.p.A, Basovizza S.S. 14, Km 163.5, 34149, Trieste, Italy
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Tresca C, Profeta G, Bisti F. Doping the Spin-Polarized Graphene Minicone on Ni(111). NANOMATERIALS (BASEL, SWITZERLAND) 2024; 14:1448. [PMID: 39269110 PMCID: PMC11396849 DOI: 10.3390/nano14171448] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2024] [Revised: 08/29/2024] [Accepted: 08/30/2024] [Indexed: 09/15/2024]
Abstract
In the attempt to induce spin-polarized states in graphene (Gr), rare-earth deposition on Gr/Co(0001) has been demonstrated to be a successful strategy: the coupling of graphene with the cobalt substrate provides spin-polarized conical-shaped states (minicone) and the rare-earth deposition brings these states at the Fermi level. In this manuscript, we theoretically explore the feasibility of an analogue approach applied on Gr/Ni(111) doped with rare-earth ions by means of density functional theory calculations. Even if not well mentioned in the literature, this system owns a minicone, similar to the cobalt case. By testing different rare-earth ions, not only do we suggest which one can provide the required doping but we also explain the effect behind this proper charge transfer.
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Affiliation(s)
- Cesare Tresca
- CNR-SPIN c/o Dipartimento di Scienze Fisiche e Chimiche, Università dell'Aquila, Via Vetoio 10, 67100 L'Aquila, Italy
| | - Gianni Profeta
- CNR-SPIN c/o Dipartimento di Scienze Fisiche e Chimiche, Università dell'Aquila, Via Vetoio 10, 67100 L'Aquila, Italy
- Dipartimento di Scienze Fisiche e Chimiche, Università dell'Aquila, Via Vetoio 10, 67100 L'Aquila, Italy
| | - Federico Bisti
- Dipartimento di Scienze Fisiche e Chimiche, Università dell'Aquila, Via Vetoio 10, 67100 L'Aquila, Italy
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3
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Sheverdyaeva PM, Bihlmayer G, Cappelluti E, Pacilé D, Mazzola F, Atodiresei N, Jugovac M, Grimaldi I, Contini G, Kundu AK, Vobornik I, Fujii J, Moras P, Carbone C, Ferrari L. Spin-Dependent ππ^{*} Gap in Graphene on a Magnetic Substrate. PHYSICAL REVIEW LETTERS 2024; 132:266401. [PMID: 38996316 DOI: 10.1103/physrevlett.132.266401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Revised: 03/06/2024] [Accepted: 05/21/2024] [Indexed: 07/14/2024]
Abstract
We present a detailed analysis of the electronic properties of graphene/Eu/Ni(111). By using angle- and spin-resolved photoemission spectroscopy and ab initio calculations, we show that the intercalation of Eu in the graphene/Ni(111) interface gives rise to a gapped freestanding dispersion of the ππ^{*} Dirac cones at the K[over ¯] point with an additional lifting of the spin degeneracy due to the mixing of graphene and Eu states. The interaction with the magnetic substrate results in a large spin-dependent gap in the Dirac cones with a topological nature characterized by a large Berry curvature and a spin-polarized Van Hove singularity, whose closeness to the Fermi level gives rise to a polaronic band.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | - Asish K Kundu
- CNR-Istituto di Struttura della Materia (CNR-ISM), Strada Statale 14, km 163.5, 34149 Trieste, Italy
- International Center for Theoretical Physics (ICTP), Trieste 34151, Italy
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, New York 11973, USA
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Muñiz Cano B, Gudín A, Sánchez-Barriga J, Clark O, Anadón A, Díez JM, Olleros-Rodríguez P, Ajejas F, Arnay I, Jugovac M, Rault J, Le Fèvre P, Bertran F, Mazhjoo D, Bihlmayer G, Rader O, Blügel S, Miranda R, Camarero J, Valbuena MA, Perna P. Rashba-like Spin Textures in Graphene Promoted by Ferromagnet-Mediated Electronic Hybridization with a Heavy Metal. ACS NANO 2024; 18:15716-15728. [PMID: 38847339 DOI: 10.1021/acsnano.4c02154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2024]
Abstract
Epitaxial graphene/ferromagnetic metal (Gr/FM) heterostructures deposited onto heavy metals have been proposed for the realization of spintronic devices because of their perpendicular magnetic anisotropy and sizable Dzyaloshinskii-Moriya interaction (DMI), allowing for both enhanced thermal stability and stabilization of chiral spin textures. However, establishing routes toward this goal requires the fundamental understanding of the microscopic origin of their unusual properties. Here, we elucidate the nature of the induced spin-orbit coupling (SOC) at Gr/Co interfaces on Ir. Through spin- and angle-resolved photoemission spectroscopy along with density functional theory, we show that the interaction of the heavy metals with the Gr layer via hybridization with the FM is the source of strong SOC in the Gr layer. Furthermore, our studies on ultrathin Co films underneath Gr reveal an energy splitting of ∼100 meV for in-plane and negligible for out-of-plane spin polarized Gr π-bands, consistent with a Rashba-SOC at the Gr/Co interface, which is either the fingerprint or the origin of the DMI. This mechanism vanishes at large Co thicknesses, where neither in-plane nor out-of-plane spin-orbit splitting is observed, indicating that Gr π-states are electronically decoupled from the heavy metal. The present findings are important for future applications of Gr-based heterostructures in spintronic devices.
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Affiliation(s)
- Beatriz Muñiz Cano
- IMDEA Nanoscience, C/Faraday 9, Campus de Cantoblanco, 28049 Madrid, Spain
| | - Adrián Gudín
- IMDEA Nanoscience, C/Faraday 9, Campus de Cantoblanco, 28049 Madrid, Spain
- Departamento de Física de la Materia Condensada, Instituto Nicolás Cabrera and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, Campus de Cantoblanco, 28049 Madrid, Spain
| | - Jaime Sánchez-Barriga
- IMDEA Nanoscience, C/Faraday 9, Campus de Cantoblanco, 28049 Madrid, Spain
- Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Street 15, 12489 Berlin, Germany
| | - Oliver Clark
- Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Street 15, 12489 Berlin, Germany
| | - Alberto Anadón
- IMDEA Nanoscience, C/Faraday 9, Campus de Cantoblanco, 28049 Madrid, Spain
| | - Jose Manuel Díez
- IMDEA Nanoscience, C/Faraday 9, Campus de Cantoblanco, 28049 Madrid, Spain
- Departamento de Física de la Materia Condensada, Instituto Nicolás Cabrera and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, Campus de Cantoblanco, 28049 Madrid, Spain
| | | | - Fernando Ajejas
- IMDEA Nanoscience, C/Faraday 9, Campus de Cantoblanco, 28049 Madrid, Spain
| | - Iciar Arnay
- IMDEA Nanoscience, C/Faraday 9, Campus de Cantoblanco, 28049 Madrid, Spain
| | - Matteo Jugovac
- Elettra Sincrotrone Trieste, Strada Statale 14 km 163.5, 34149 Trieste, Italy
| | - Julien Rault
- Synchrotron SOLEIL, Saint-Aubin, 91192 Gif-sur-Yvette, France
| | | | | | - Donya Mazhjoo
- Peter Grünberg Institute and Institute for Advanced Simulation, Forschungszentrum Jülich, D-52425 Jülich, Germany
| | - Gustav Bihlmayer
- Peter Grünberg Institute and Institute for Advanced Simulation, Forschungszentrum Jülich, D-52425 Jülich, Germany
| | - Oliver Rader
- Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Street 15, 12489 Berlin, Germany
| | - Stefan Blügel
- Peter Grünberg Institute and Institute for Advanced Simulation, Forschungszentrum Jülich, D-52425 Jülich, Germany
| | - Rodolfo Miranda
- IMDEA Nanoscience, C/Faraday 9, Campus de Cantoblanco, 28049 Madrid, Spain
- Departamento de Física de la Materia Condensada, Instituto Nicolás Cabrera and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, Campus de Cantoblanco, 28049 Madrid, Spain
| | - Julio Camarero
- IMDEA Nanoscience, C/Faraday 9, Campus de Cantoblanco, 28049 Madrid, Spain
- Departamento de Física de la Materia Condensada, Instituto Nicolás Cabrera and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, Campus de Cantoblanco, 28049 Madrid, Spain
| | | | - Paolo Perna
- IMDEA Nanoscience, C/Faraday 9, Campus de Cantoblanco, 28049 Madrid, Spain
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Hu J, Han Y, Chi X, Omar GJ, Al Ezzi MME, Gou J, Yu X, Andrivo R, Watanabe K, Taniguchi T, Wee ATS, Qiao Z, Ariando A. Tunable Spin-Polarized States in Graphene on a Ferrimagnetic Oxide Insulator. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2305763. [PMID: 37811809 DOI: 10.1002/adma.202305763] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Revised: 10/01/2023] [Indexed: 10/10/2023]
Abstract
Spin-polarized two-dimensional (2D) materials with large and tunable spin-splitting energy promise the field of 2D spintronics. While graphene has been a canonical 2D material, its spin properties and tunability are limited. Here, this work demonstrates the emergence of robust spin-polarization in graphene with large and tunable spin-splitting energy of up to 132 meV at zero applied magnetic fields. The spin polarization is induced through a magnetic exchange interaction between graphene and the underlying ferrimagnetic oxide insulating layer, Tm3 Fe5 O12 , as confirmed by its X-ray magnetic circular dichroism (XMCD). The spin-splitting energies are directly measured and visualized by the shift in their Landau-fan diagram mapped by analyzing the measured Shubnikov-de-Haas (SdH) oscillations as a function of applied electric fields, showing consistent fit with the first-principles and machine learning calculations. Further, the observed spin-splitting energies can be tuned over a broad range between 98 and 166 meV by field cooling. The methods and results are applicable to other 2D (magnetic) materials and heterostructures, and offer great potential for developing next-generation spin logic and memory devices.
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Affiliation(s)
- Junxiong Hu
- Department of Physics, National University of Singapore, Singapore, 117542, Singapore
- Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore, 117551, Singapore
| | - Yulei Han
- International Center for Quantum Design of Functional Materials, CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China
- Department of Physics, Fuzhou University, Fuzhou, Fujian, 350108, China
| | - Xiao Chi
- Department of Physics, National University of Singapore, Singapore, 117542, Singapore
- Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, Singapore, 117603, Singapore
| | - Ganesh Ji Omar
- Department of Physics, National University of Singapore, Singapore, 117542, Singapore
| | - Mohammed Mohammed Esmail Al Ezzi
- Department of Physics, National University of Singapore, Singapore, 117542, Singapore
- Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore, 117551, Singapore
| | - Jian Gou
- Department of Physics, National University of Singapore, Singapore, 117542, Singapore
| | - Xiaojiang Yu
- Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, Singapore, 117603, Singapore
| | - Rusydi Andrivo
- Department of Physics, National University of Singapore, Singapore, 117542, Singapore
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Ibaraki, 305-0044, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Ibaraki, 305-0044, Japan
| | - Andrew Thye Shen Wee
- Department of Physics, National University of Singapore, Singapore, 117542, Singapore
| | - Zhenhua Qiao
- International Center for Quantum Design of Functional Materials, CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei, 230088, China
| | - A Ariando
- Department of Physics, National University of Singapore, Singapore, 117542, Singapore
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