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Vlaic S, Rougemaille N, Artaud A, Renard V, Huder L, Rouvière JL, Kimouche A, Santos B, Locatelli A, Guisset V, David P, Chapelier C, Magaud L, Canals B, Coraux J. Graphene as a Mechanically Active, Deformable Two-Dimensional Surfactant. J Phys Chem Lett 2018; 9:2523-2531. [PMID: 29688019 DOI: 10.1021/acs.jpclett.8b00586] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
In crystal growth, surfactants are additive molecules used in dilute amount or as dense, permeable layers to control surface morphologies. We investigate the properties of a strikingly different surfactant: a 2D and covalent layer with close atomic packing, graphene. Using in situ, real-time electron microscopy, scanning tunneling microscopy, kinetic Monte Carlo simulations, and continuum mechanics calculations, we reveal why metallic atomic layers can grow in a 2D manner below an impermeable graphene membrane. Upon metal growth, graphene dynamically opens nanochannels called wrinkles, facilitating mass transport while at the same time storing and releasing elastic energy via lattice distortions. Graphene thus behaves as a mechanically active, deformable surfactant. The wrinkle-driven mass transport of the metallic layer intercalated between graphene and the substrate is observed for two graphene-based systems, characterized by different physicochemical interactions, between graphene and the substrate and between the intercalated material and graphene. The deformable surfactant character of graphene that we unveil should then apply to a broad variety of species, opening new avenues for using graphene as a 2D surfactant forcing the growth of flat films, nanostructures, and unconventional crystalline phases.
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Affiliation(s)
- Sergio Vlaic
- Univ. Grenoble Alpes, CNRS, Institut NEEL , Grenoble INP , 38000 Grenoble , France
- LPEM, ESPCI Paris, PSL Research University , CNRS, Sorbonne Universités, UPMC University of Paris 6 , 10 rue Vauquelin , Paris F-75005 , France
| | - Nicolas Rougemaille
- Univ. Grenoble Alpes, CNRS, Institut NEEL , Grenoble INP , 38000 Grenoble , France
| | - Alexandre Artaud
- Univ. Grenoble Alpes , CEA, INAC, PHELIQS, MEM , 38000 Grenoble , France
| | - Vincent Renard
- Univ. Grenoble Alpes , CEA, INAC, PHELIQS, MEM , 38000 Grenoble , France
| | - Loïc Huder
- Univ. Grenoble Alpes , CEA, INAC, PHELIQS, MEM , 38000 Grenoble , France
| | - Jean-Luc Rouvière
- Univ. Grenoble Alpes , CEA, INAC, PHELIQS, MEM , 38000 Grenoble , France
| | - Amina Kimouche
- Univ. Grenoble Alpes, CNRS, Institut NEEL , Grenoble INP , 38000 Grenoble , France
| | - Benito Santos
- Elettra-Sincrotrone Trieste S.C.p.A. , Strada Statale 14 - km 163,5 in AREA Science Park , I-34149 Basovizza , Trieste , Italy
| | - Andrea Locatelli
- Elettra-Sincrotrone Trieste S.C.p.A. , Strada Statale 14 - km 163,5 in AREA Science Park , I-34149 Basovizza , Trieste , Italy
| | - Valérie Guisset
- Univ. Grenoble Alpes, CNRS, Institut NEEL , Grenoble INP , 38000 Grenoble , France
| | - Philippe David
- Univ. Grenoble Alpes, CNRS, Institut NEEL , Grenoble INP , 38000 Grenoble , France
| | - Claude Chapelier
- Univ. Grenoble Alpes , CEA, INAC, PHELIQS, MEM , 38000 Grenoble , France
| | - Laurence Magaud
- Univ. Grenoble Alpes, CNRS, Institut NEEL , Grenoble INP , 38000 Grenoble , France
| | - Benjamin Canals
- Univ. Grenoble Alpes, CNRS, Institut NEEL , Grenoble INP , 38000 Grenoble , France
| | - Johann Coraux
- Univ. Grenoble Alpes, CNRS, Institut NEEL , Grenoble INP , 38000 Grenoble , France
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Graphene-based synthetic antiferromagnets and ferrimagnets. Nat Commun 2017; 8:699. [PMID: 28951545 PMCID: PMC5615057 DOI: 10.1038/s41467-017-00825-9] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Accepted: 07/25/2017] [Indexed: 11/23/2022] Open
Abstract
Graphene-spaced magnetic systems with antiferromagnetic exchange-coupling offer exciting opportunities for emerging technologies. Unfortunately, the in-plane graphene-mediated exchange-coupling found so far is not appropriate for realistic exploitation, due to being weak, being of complex nature, or requiring low temperatures. Here we establish that ultra-thin Fe/graphene/Co films grown on Ir(111) exhibit robust perpendicular antiferromagnetic exchange-coupling, and gather a collection of magnetic properties well-suited for applications. Remarkably, the observed exchange coupling is thermally stable above room temperature, strong but field controllable, and occurs in perpendicular orientation with opposite remanent layer magnetizations. Atomistic first-principles simulations provide further ground for the feasibility of graphene-spaced antiferromagnetic coupled structures, confirming graphene’s direct role in sustaining antiferromagnetic superexchange-coupling between the magnetic films. These results provide a path for the realization of graphene-based perpendicular synthetic antiferromagnetic systems, which seem exciting for fundamental nanoscience or potential use in spintronic devices. Antiferromagnetic spintronics may pave the way to innovative information storage devices with perpendicular coupling, however experimental demonstrations are still sparse. Here, the authors demonstrate a graphene-mediated perpendicular antiferromagnetic coupling between Fe and Co layers in a Fe/graphene/Co sandwich structure.
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Vu AD, Coraux J, Chen G, N'Diaye AT, Schmid AK, Rougemaille N. Unconventional magnetisation texture in graphene/cobalt hybrids. Sci Rep 2016; 6:24783. [PMID: 27114039 PMCID: PMC4844999 DOI: 10.1038/srep24783] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2015] [Accepted: 04/06/2016] [Indexed: 11/15/2022] Open
Abstract
Magnetic domain structure and spin-dependent reflectivity measurements on cobalt thin films intercalated at the graphene/Ir(111) interface are investigated using spin-polarised low-energy electron microscopy. We find that graphene-covered cobalt films have surprising magnetic properties. Vectorial imaging of magnetic domains reveals an unusually gradual thickness-dependent spin reorientation transition, in which magnetisation rotates from out-of-the-film plane to the in-plane direction by less than 10° per cobalt monolayer. During this transition, cobalt films have a meandering spin texture, characterised by a complex, three-dimensional, wavy magnetisation pattern. In addition, spectroscopy measurements suggest that the electronic band structure of the unoccupied states is essentially spin-independent already a few electron-Volts above the vacuum level. These properties strikingly differ from those of pristine cobalt films and could open new prospects in surface magnetism.
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Affiliation(s)
- A D Vu
- CNRS, Inst NEEL, F-38000 Grenoble, France.,Univ. Grenoble Alpes, Inst NEEL, F-38000 Grenoble, France
| | - J Coraux
- CNRS, Inst NEEL, F-38000 Grenoble, France.,Univ. Grenoble Alpes, Inst NEEL, F-38000 Grenoble, France
| | - G Chen
- NCEM, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - A T N'Diaye
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - A K Schmid
- NCEM, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - N Rougemaille
- CNRS, Inst NEEL, F-38000 Grenoble, France.,Univ. Grenoble Alpes, Inst NEEL, F-38000 Grenoble, France
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Yang H, Vu AD, Hallal A, Rougemaille N, Coraux J, Chen G, Schmid AK, Chshiev M. Anatomy and Giant Enhancement of the Perpendicular Magnetic Anisotropy of Cobalt-Graphene Heterostructures. NANO LETTERS 2016; 16:145-51. [PMID: 26641927 DOI: 10.1021/acs.nanolett.5b03392] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
We report strongly enhanced perpendicular magnetic anisotropy (PMA) of Co films by graphene coating from both first-principles and experiments. Our calculations show that graphene can dramatically boost the surface anisotropy of Co films up to twice the value of its pristine counterpart and can extend the out-of-plane effective anisotropy up to unprecedented thickness of 25 Å. These findings are supported by our experiments on graphene coating on Co films grown on Ir substrate. Furthermore, we report layer-resolved and orbital-hybridization-resolved anisotropy analysis, which help understanding of the physical mechanisms of PMA and more practically can help design structures with giant PMA. As an example, we propose superexchange stabilized Co-graphene heterostructures with a robust constant effective PMA and linearly increasing interfacial anisotropy as a function of film thickness. These findings point toward possibilities to engineer graphene/ferromagnetic metal heterostructures with giant magnetic anisotropy more than 20-times larger compared to conventional multilayers, which constitutes a hallmark for future graphene and traditional spintronic technologies.
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Affiliation(s)
- Hongxin Yang
- Univ. Grenoble Alpes, INAC-SPINTEC , F-38000 Grenoble, France
- CNRS, SPINTEC , F-38000 Grenoble, France
- CEA, INAC-SPINTEC , F-38000 Grenoble, France
| | - Anh Duc Vu
- Univ. Grenoble Alples, Inst. NEEL , F-38000 Grenoble, France
- CNRS, Inst. NEEL , F-38000 Grenoble, France
| | - Ali Hallal
- Univ. Grenoble Alpes, INAC-SPINTEC , F-38000 Grenoble, France
- CNRS, SPINTEC , F-38000 Grenoble, France
- CEA, INAC-SPINTEC , F-38000 Grenoble, France
| | - Nicolas Rougemaille
- Univ. Grenoble Alples, Inst. NEEL , F-38000 Grenoble, France
- CNRS, Inst. NEEL , F-38000 Grenoble, France
| | - Johann Coraux
- Univ. Grenoble Alples, Inst. NEEL , F-38000 Grenoble, France
- CNRS, Inst. NEEL , F-38000 Grenoble, France
| | - Gong Chen
- NCEM, Molecular Foundry, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States
| | - Andreas K Schmid
- NCEM, Molecular Foundry, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States
| | - Mairbek Chshiev
- Univ. Grenoble Alpes, INAC-SPINTEC , F-38000 Grenoble, France
- CNRS, SPINTEC , F-38000 Grenoble, France
- CEA, INAC-SPINTEC , F-38000 Grenoble, France
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