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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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Nath M, Joshi S, Mishra S. Ab initio calculation of magnetic anisotropy and thermal spin transition in the variable temperature crystal conformations of [Co(terpy) 2] 2. Phys Chem Chem Phys 2024; 26:15405-15416. [PMID: 38747204 DOI: 10.1039/d4cp00591k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2024]
Abstract
The structure-property correlation of [Co(terpy)2]2+, which shows a spin crossover at 270 K, has been computationally investigated based on its variable temperature crystal structures. Among the employed DFT functionals, only the re-parametrized hybrid B3LYP* functional could describe the correct spin transition temperature. Explicit consideration of metal-ligand sigma bonding with dynamic electron correlation is found to be necessary for an accurate determination of the SCO temperature with multi-reference calculations. The metal-ligand axial bond distances are found to be the most significant internal coordinates in deciding SCO. A small structural change along the axial distance causes a change in the t2g orbital splitting pattern and a reorientation of the magnetization axes at the SCO temperature. The complex shows an unusual triaxial magnetic anisotropy, with an easy axis of magnetization developing at higher temperatures. The strong coupling of low-frequency wagging motion of the two terpyridine ligands with the spin states of the complex provides an effective pathway for the relaxation of magnetization, resulting in a small magnetic anisotropy barrier.
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Affiliation(s)
- Moromi Nath
- Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur, India.
| | - Shalini Joshi
- Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur, India.
| | - Sabyashachi Mishra
- Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur, India.
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Jugovac M, Cojocariu I, Sánchez-Barriga J, Gargiani P, Valvidares M, Feyer V, Blügel S, Bihlmayer G, Perna P. Inducing Single Spin-Polarized Flat Bands in Monolayer Graphene. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2301441. [PMID: 37036386 DOI: 10.1002/adma.202301441] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Revised: 03/27/2023] [Indexed: 06/19/2023]
Abstract
Due to the fundamental and technological implications in driving the appearance of non-trivial, exotic topological spin textures and emerging symmetry-broken phases, flat electronic bands in 2D materials, including graphene, are nowadays a relevant topic in the field of spintronics. Here, via europium doping, single spin-polarized bands are generated in monolayer graphene supported by the Co(0001) surface. The doping is controlled by Eu positioning, allowing for the formation of aK ¯ $\bar{\mathrm{K}}$ -valley localized single spin-polarized low-dispersive parabolic band close to the Fermi energy when Eu is on top, and of a π* flat band with single spin character when Eu is intercalated underneath graphene. In the latter case, Eu also induces a bandgap opening at the Dirac point while the Eu 4f states act as a spin filter, splitting the π band into two spin-polarized branches. The generation of flat bands with single spin character, as revealed by the spin- and angle-resolved photoemission spectroscopy (ARPES) experiments, complemented by density functional theory (DFT) calculations, opens up new pathways toward the realization of spintronic devices exploiting such novel exotic electronic and magnetic states.
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Affiliation(s)
- Matteo Jugovac
- Elettra - Sincrotrone Trieste, S.S. 14 - km 163.5, Basovizza, 34149, Trieste, Italy
| | - Iulia Cojocariu
- Elettra - Sincrotrone Trieste, S.S. 14 - km 163.5, Basovizza, 34149, Trieste, Italy
- Peter Grünberg Institute (PGI-6), Forschungszentrum Jülich GmbH, 52425, Jülich, Germany
- Dipartimento di Fisica, Università degli studi di Trieste, Via A. Valerio 2, 34127, Trieste, Italy
| | - Jaime Sánchez-Barriga
- Helmholtz-Zentrum Berlin für Materialien und Energie, Elektronenspeicherring BESSY II, Albert-Einstein-Str. 15, 12489, Berlin, Germany
- IMDEA Nanociencia, Campus de Cantoblanco, c/ Faraday 9, 28049, Madrid, Spain
| | | | | | - Vitaliy Feyer
- Peter Grünberg Institute (PGI-6), Forschungszentrum Jülich GmbH, 52425, Jülich, Germany
| | - Stefan Blügel
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425, Jülich, Germany
| | - Gustav Bihlmayer
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425, Jülich, Germany
| | - Paolo Perna
- IMDEA Nanociencia, Campus de Cantoblanco, c/ Faraday 9, 28049, Madrid, Spain
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Two-dimensional materials prospects for non-volatile spintronic memories. Nature 2022; 606:663-673. [PMID: 35732761 DOI: 10.1038/s41586-022-04768-0] [Citation(s) in RCA: 63] [Impact Index Per Article: 31.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Accepted: 04/19/2022] [Indexed: 01/12/2023]
Abstract
Non-volatile magnetic random-access memories (MRAMs), such as spin-transfer torque MRAM and next-generation spin-orbit torque MRAM, are emerging as key to enabling low-power technologies, which are expected to spread over large markets from embedded memories to the Internet of Things. Concurrently, the development and performances of devices based on two-dimensional van der Waals heterostructures bring ultracompact multilayer compounds with unprecedented material-engineering capabilities. Here we provide an overview of the current developments and challenges in regard to MRAM, and then outline the opportunities that can arise by incorporating two-dimensional material technologies. We highlight the fundamental properties of atomically smooth interfaces, the reduced material intermixing, the crystal symmetries and the proximity effects as the key drivers for possible disruptive improvements for MRAM at advanced technology nodes.
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Lii-Rosales A, Han Y, Jing D, Tringides MC, Julien S, Wan KT, Wang CZ, Lai KC, Evans JW, Thiel PA. Encapsulation of metal nanoparticles at the surface of a prototypical layered material. NANOSCALE 2021; 13:1485-1506. [PMID: 33439199 DOI: 10.1039/d0nr07024f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Encapsulation of metal nanoparticles just below the surface of a prototypical layered material, graphite, is a recently discovered phenomenon. These encapsulation architectures have potential for tuning the properties of two-dimensional or layered materials, and additional applications might exploit the properties of the encapsulated metal nanoclusters themselves. The encapsulation process produces novel surface nanostructures and can be achieved for a variety of metals. Given that these studies of near-surface intercalation are in their infancy, these systems provide a rich area for future studies. This Review presents the current progress on the encapsulation, including experimental strategies and characterization, as well as theoretical understanding which leads to the development of predictive capability. The Review closes with future opportunities where further understanding of the encapsulation is desired to exploit its applications.
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Ajejas F, Anadon A, Gudin A, Diez JM, Ayani CG, Olleros-Rodríguez P, de Melo Costa L, Navío C, Gutierrez A, Calleja F, Vázquez de Parga AL, Miranda R, Camarero J, Perna P. Thermally Activated Processes for Ferromagnet Intercalation in Graphene-Heavy Metal Interfaces. ACS APPLIED MATERIALS & INTERFACES 2020; 12:4088-4096. [PMID: 31875389 DOI: 10.1021/acsami.9b19159] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The development of graphene (Gr) spintronics requires the ability to engineer epitaxial Gr heterostructures with interfaces of high quality, in which the intrinsic properties of Gr are modified through proximity with a ferromagnet to allow for efficient room temperature spin manipulation or the stabilization of new magnetic textures. These heterostructures can be prepared in a controlled way by intercalation through graphene of different metals. Using photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM), we achieve a nanoscale control of thermally activated intercalation of a homogeneous ferromagnetic (FM) layer underneath epitaxial Gr grown onto (111)-oriented heavy metal (HM) buffers deposited, in turn, onto insulating oxide surfaces. XPS and STM demonstrate that Co atoms evaporated on top of Gr arrange in 3D clusters and, upon thermal annealing, penetrate through and diffuse below Gr in a 2D fashion. The complete intercalation of the metal occurs at specific temperatures, depending on the type of metallic buffer. The activation energy and the optimum temperature for the intercalation processes are determined. We describe a reliable method to fabricate and characterize in situ high-quality Gr-FM/HM heterostructures, enabling the realization of novel spin-orbitronic devices that exploit the extraordinary properties of Gr.
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Affiliation(s)
- Fernando Ajejas
- IMDEA Nanociencia , c/ Faraday 9, Campus de Cantoblanco , 28049 Madrid , Spain
- Departamento Física de la Materia Condensada & Instituto "Nicolás Cabrera" , Universidad Autónoma de Madrid , 28049 Madrid , Spain
| | - Alberto Anadon
- IMDEA Nanociencia , c/ Faraday 9, Campus de Cantoblanco , 28049 Madrid , Spain
| | - Adrian Gudin
- IMDEA Nanociencia , c/ Faraday 9, Campus de Cantoblanco , 28049 Madrid , Spain
- Departamento Física de la Materia Condensada & Instituto "Nicolás Cabrera" , Universidad Autónoma de Madrid , 28049 Madrid , Spain
| | - José Manuel Diez
- IMDEA Nanociencia , c/ Faraday 9, Campus de Cantoblanco , 28049 Madrid , Spain
- Departamento Física de la Materia Condensada & Instituto "Nicolás Cabrera" , Universidad Autónoma de Madrid , 28049 Madrid , Spain
| | - Cosme G Ayani
- IMDEA Nanociencia , c/ Faraday 9, Campus de Cantoblanco , 28049 Madrid , Spain
| | | | | | - Cristina Navío
- IMDEA Nanociencia , c/ Faraday 9, Campus de Cantoblanco , 28049 Madrid , Spain
| | - Alejandro Gutierrez
- Departamento Física Aplicada & Instituto "Nicolás Cabrera" , Universidad Autónoma de Madrid , 28049 Madrid , Spain
| | - Fabian Calleja
- IMDEA Nanociencia , c/ Faraday 9, Campus de Cantoblanco , 28049 Madrid , Spain
| | - Amadeo L Vázquez de Parga
- IMDEA Nanociencia , c/ Faraday 9, Campus de Cantoblanco , 28049 Madrid , Spain
- Departamento Física de la Materia Condensada & Instituto "Nicolás Cabrera" , Universidad Autónoma de Madrid , 28049 Madrid , Spain
- IFIMAC, Universidad Autónoma de Madrid , 28049 Madrid , Spain
| | - Rodolfo Miranda
- IMDEA Nanociencia , c/ Faraday 9, Campus de Cantoblanco , 28049 Madrid , Spain
- Departamento Física de la Materia Condensada & Instituto "Nicolás Cabrera" , Universidad Autónoma de Madrid , 28049 Madrid , Spain
- IFIMAC, Universidad Autónoma de Madrid , 28049 Madrid , Spain
| | - Julio Camarero
- IMDEA Nanociencia , c/ Faraday 9, Campus de Cantoblanco , 28049 Madrid , Spain
- Departamento Física de la Materia Condensada & Instituto "Nicolás Cabrera" , Universidad Autónoma de Madrid , 28049 Madrid , Spain
- IFIMAC, Universidad Autónoma de Madrid , 28049 Madrid , Spain
| | - Paolo Perna
- IMDEA Nanociencia , c/ Faraday 9, Campus de Cantoblanco , 28049 Madrid , Spain
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Cuadrado R, Pruneda M. Guidelines for Selecting Interlayer Spacers in Synthetic 2D-Based Antiferromagnets from First-Principles Simulations. NANOMATERIALS (BASEL, SWITZERLAND) 2019; 9:E1764. [PMID: 31835819 PMCID: PMC6955936 DOI: 10.3390/nano9121764] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Revised: 12/05/2019] [Accepted: 12/06/2019] [Indexed: 06/10/2023]
Abstract
Following the recent synthesis of graphene-based antiferromagnetic ultrathin heterostructures made of Co and Fe, we analyse the effect of the spacer between both ferromagnetic materials. Using density functional calculations, we carried out an exhaustive study of the geometric, electronic and magnetic properties for intercalated single Co MLs on top of Ir(111) coupled to monolayered Fe through n graphene layers (n = 1, 2, 3) or monolayered h-BN. Different local atomic arrangements have been considered to model the Moiré patterns expected in these heterostructures. The magnetic exchange interactions between both ferromagnets ( J C o - F e ) are computed from explicit calculations of parallel and anti-parallel Fe/Co inter-layer alignments, and discussed in the context of recent experiments. Our analysis confirms that the robust antiferromagnetic superexchange-coupling between Fe and Co layers is mediated by the graphene spacer through the hybridization of C's p z orbitals with Fe and Co's 3d states. The hybridization is substantially suppressed for multilayered graphene spacers, for which the magnetic coupling between ferromagnets is critically reduced, suggesting the need for ultrathin (monolayer) spacers in the design of synthetic graphene-based antiferromagnets. In the case of h-BN, p z orbitals also mediate d(Fe/Co) coupling. However, there is a larger contribution of local ferromagnetic interactions. Magnetic anisotropy energies were also calculated using a fully relativistic description, and show out-of-plane easy axis for all the configurations, with remarkable net values in the range from 1 to 4 meV.
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Affiliation(s)
- Ramón Cuadrado
- Catalan Institute of Nanoscience and Nanotechnology - ICN2, CSIC and BIST, Campus UAB, 08193 Bellaterra, Spain
- Universitat Autonoma de Barcelona, 08193 Bellaterra (Cerdanyola del Valles), Spain
| | - Miguel Pruneda
- Catalan Institute of Nanoscience and Nanotechnology - ICN2, CSIC and BIST, Campus UAB, 08193 Bellaterra, Spain
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Chen W, Xiao P, Chen H, Zhang H, Zhang Q, Chen Y. Polymeric Graphene Bulk Materials with a 3D Cross-Linked Monolithic Graphene Network. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2019; 31:e1802403. [PMID: 30118541 DOI: 10.1002/adma.201802403] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2018] [Revised: 06/06/2018] [Indexed: 06/08/2023]
Abstract
Although many great potential applications are proposed for graphene, till now none are yet realized as a stellar application. The most challenging issue for such practical applications is to figure out how to prepare graphene bulk materials while maintaining the unique two-dimensional (2D) structure and the many excellent properties of graphene sheets. Herein, such polymeric graphene bulk materials containing three-dimensional (3D) cross-linked networks with graphene sheets as the building unit are reviewed. The theoretical research on various proposed structures of graphene bulk materials is summarized first. Then, the synthesis or fabrication of these graphene materials is described, which comprises mainly two approaches: chemical vapor deposition and cross-linking using graphene oxide directly. Finally, some exotic and exciting potential applications of these graphene bulk materials are presented.
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Affiliation(s)
- Wangqiao Chen
- State Key Laboratory and Institute of Elemento-Organic Chemistry, Centre of Nanoscale Science and Technology and Key Laboratory of Functional Polymer Materials, College of Chemistry, Nankai University, Tianjin, 300071, China
- School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798
| | - Peishuang Xiao
- State Key Laboratory and Institute of Elemento-Organic Chemistry, Centre of Nanoscale Science and Technology and Key Laboratory of Functional Polymer Materials, College of Chemistry, Nankai University, Tianjin, 300071, China
| | - Honghui Chen
- State Key Laboratory and Institute of Elemento-Organic Chemistry, Centre of Nanoscale Science and Technology and Key Laboratory of Functional Polymer Materials, College of Chemistry, Nankai University, Tianjin, 300071, China
| | - Hongtao Zhang
- State Key Laboratory and Institute of Elemento-Organic Chemistry, Centre of Nanoscale Science and Technology and Key Laboratory of Functional Polymer Materials, College of Chemistry, Nankai University, Tianjin, 300071, China
| | - Qichun Zhang
- School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798
| | - Yongsheng Chen
- State Key Laboratory and Institute of Elemento-Organic Chemistry, Centre of Nanoscale Science and Technology and Key Laboratory of Functional Polymer Materials, College of Chemistry, Nankai University, Tianjin, 300071, China
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Avvisati G, Gargiani P, Mondelli P, Presel F, Bignardi L, Baraldi A, Betti MG. Metal phthalocyanines interaction with Co mediated by a moiré graphene superlattice. J Chem Phys 2019; 150:054704. [PMID: 30736689 DOI: 10.1063/1.5080533] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The assembling of metal phthalocyanines on the rippled moiré superlattice of graphene/Ir(111) intercalated with one Co layer is driven by the site-dependent polarization field induced by the incommensurate graphene-Co interface. We have performed an X-ray absorption and photoemission study to unveil the role of the metallic centers and of the organic ligands in the molecule-Co interaction process mediated by graphene. Notably, we consider different electronic molecular orbitals, i.e. phthalocyanines with Cu and Mn metallic ions. The spectroscopic response suggests almost unaltered CuPc molecular states upon adsorption, and the rippled graphene carpet decouples completely the electronic interaction between the molecules and the Co layer, while a slight hybridization is present for MnPcs. MnPc molecules, trapped in the valleys of the moiré graphene superlattice, slightly intermix, through the orbitals protruding out of the molecular plane, with the underlying Co, while the organic ligands are almost unaltered. Graphene acts as an interlayer and mediates the interaction between metal phthalocyanines and the metallic substrate, preventing a strong chemical intermixing and enabling the assembly of almost unaltered molecules, preserving their electronic/magnetic state.
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Affiliation(s)
- Giulia Avvisati
- Sapienza University of Rome, Piazzale Aldo Moro, 5, I-00185 Rome, Italy
| | - Pierluigi Gargiani
- ALBA Synchrotron Light Source, Carrer de la Llum, 2-26, E-08290 Barcelona, Spain
| | | | - Francesco Presel
- Physics Department, University of Trieste, Via Valerio, 2, I-34127 Trieste, Italy
| | - Luca Bignardi
- Elettra Sincrotrone Trieste, S.S. 14, Km 163.5, I-34149 Basovizza, Trieste Italy
| | - Alessandro Baraldi
- Physics Department, University of Trieste, Via Valerio, 2, I-34127 Trieste, Italy
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Ajejas F, Gudín A, Guerrero R, Anadón Barcelona A, Diez JM, de Melo Costa L, Olleros P, Niño MA, Pizzini S, Vogel J, Valvidares M, Gargiani P, Cabero M, Varela M, Camarero J, Miranda R, Perna P. Unraveling Dzyaloshinskii-Moriya Interaction and Chiral Nature of Graphene/Cobalt Interface. NANO LETTERS 2018; 18:5364-5372. [PMID: 30052462 DOI: 10.1021/acs.nanolett.8b00878] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
A major challenge for future spintronics is to develop suitable spin transport channels with long spin lifetime and propagation length. Graphene can meet these requirements, even at room temperature. On the other side, taking advantage of the fast motion of chiral textures, that is, Néel-type domain walls and magnetic skyrmions, can satisfy the demands for high-density data storage, low power consumption, and high processing speed. We have engineered epitaxial structures where an epitaxial ferromagnetic Co layer is sandwiched between an epitaxial Pt(111) buffer grown in turn onto MgO(111) substrates and a graphene layer. We provide evidence of a graphene-induced enhancement of the perpendicular magnetic anisotropy up to 4 nm thick Co films and of the existence of chiral left-handed Néel-type domain walls stabilized by the effective Dzyaloshinskii-Moriya interaction (DMI) in the stack. The experiments show evidence of a sizable DMI at the gr/Co interface, which is described in terms of a conduction electron mediated Rashba-DMI mechanism and points opposite to the spin orbit coupling-induced DMI at the Co/Pt interface. In addition, the presence of graphene results in (i) a surfactant action for the Co growth, producing an intercalated, flat, highly perfect face-centered cubic film, pseudomorphic with Pt and (ii) an efficient protection from oxidation. The magnetic chiral texture is stable at room temperature and grown on insulating substrate. Our findings open new routes to control chiral spin structures using interfacial engineering in graphene-based systems for future spin-orbitronics devices fully integrated on oxide substrates.
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Affiliation(s)
- Fernando Ajejas
- IMDEA Nanociencia, 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
| | - Adrian Gudín
- IMDEA Nanociencia, 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
| | - Ruben Guerrero
- IMDEA Nanociencia, Campus de Cantoblanco , 28049 Madrid , Spain
| | | | | | | | - Pablo Olleros
- IMDEA Nanociencia, Campus de Cantoblanco , 28049 Madrid , Spain
| | | | - Stefania Pizzini
- Université Grenoble Alpes, CNRS, Institut Néel , 38000 Grenoble , France
| | - Jan Vogel
- Université Grenoble Alpes, CNRS, Institut Néel , 38000 Grenoble , France
| | - Manuel Valvidares
- ALBA Synchrotron Light Source, Cerdanyola del Vallès , 08290 Barcelona , Spain
| | - Pierluigi Gargiani
- ALBA Synchrotron Light Source, Cerdanyola del Vallès , 08290 Barcelona , Spain
| | - Mariona Cabero
- Departamento de Física de Materiales, Instituto de Magnetismo Aplicado and Instituto Pluridisciplinar , Universidad Complutense de Madrid, Ciudad Universitaria 28040 , Madrid , Spain
| | - Maria Varela
- Departamento de Física de Materiales, Instituto de Magnetismo Aplicado and Instituto Pluridisciplinar , Universidad Complutense de Madrid, Ciudad Universitaria 28040 , Madrid , Spain
| | - Julio Camarero
- IMDEA Nanociencia, 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
| | - Rodolfo Miranda
- IMDEA Nanociencia, 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 Nanociencia, Campus de Cantoblanco , 28049 Madrid , Spain
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Genoni P, Genuzio F, Menteş TO, Santos B, Sala A, Lenardi C, Locatelli A. Magnetic Patterning by Electron Beam-Assisted Carbon Lithography. ACS APPLIED MATERIALS & INTERFACES 2018; 10:27178-27187. [PMID: 30019889 DOI: 10.1021/acsami.8b07485] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We report on the proof of principle of a scalable method for writing the magnetic state by electron-stimulated molecular dissociative adsorption on ultrathin Co on Re(0001). Intense microfocused low-energy electron beams are used to promote the formation of surface carbides and graphitic carbon through the fragmentation of carbon monoxide. Upon annealing at the CO desorption temperature, carbon persists in the irradiated areas, whereas the clean surface is recovered elsewhere, giving origin to chemical patterns with nanometer-sharp edges. The accumulation of carbon is found to induce an in-plane to out-of-plane spin reorientation transition in Co, manifested by the appearance of striped magnetic domains. Irradiation at doses in excess of 1000 L of CO followed by ultrahigh vacuum annealing at 380 °C determines the formation of a graphitic overlayer in the irradiated areas, under which Co exhibits out-of-plane magnetic anisotropy. Domains with opposite magnetization are separated here by chiral Neél walls. Our fabrication protocol adds lateral control to spin reorientation transitions, permitting to tune the magnetic anisotropy within arbitrary regions of mesoscopic size. We envisage applications in the nano-engineering of graphene-spaced stacks exhibiting the desired magnetic state and properties.
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Affiliation(s)
- Pietro Genoni
- CIMAINA, Department of Physics , Università degli Studi di Milano , via Celoria 16 , I-20133 Milan , Italy
| | - Francesca Genuzio
- Elettra-Sincrotrone Trieste , S.S. 14 km 163.5 in AREA Science Park , Basovizza, I-34149 Trieste , Italy
| | - Tevfik Onur Menteş
- Elettra-Sincrotrone Trieste , S.S. 14 km 163.5 in AREA Science Park , Basovizza, I-34149 Trieste , Italy
| | - Benito Santos
- Elettra-Sincrotrone Trieste , S.S. 14 km 163.5 in AREA Science Park , Basovizza, I-34149 Trieste , Italy
| | - Alessandro Sala
- Elettra-Sincrotrone Trieste , S.S. 14 km 163.5 in AREA Science Park , Basovizza, I-34149 Trieste , Italy
- Department of Physics , Università degli Studi di Trieste , via Valerio 2 , I-34127 Trieste , Italy
| | - Cristina Lenardi
- CIMAINA, Department of Physics , Università degli Studi di Milano , via Celoria 16 , I-20133 Milan , Italy
| | - Andrea Locatelli
- Elettra-Sincrotrone Trieste , S.S. 14 km 163.5 in AREA Science Park , Basovizza, I-34149 Trieste , Italy
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Avvisati G, Cardoso C, Varsano D, Ferretti A, Gargiani P, Betti MG. Ferromagnetic and Antiferromagnetic Coupling of Spin Molecular Interfaces with High Thermal Stability. NANO LETTERS 2018; 18:2268-2273. [PMID: 29558616 DOI: 10.1021/acs.nanolett.7b04836] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We report an advanced organic spin-interface architecture with magnetic remanence at room temperature, constituted by metal phthalocyanine molecules magnetically coupled with Co layer(s), mediated by graphene. Fe- and Cu-phthalocyanines assembled on graphene/Co have identical structural configurations, but FePc couples antiferromagnetically with Co up to room temperature, while CuPc couples ferromagnetically with weaker coupling and thermal stability, as deduced by element-selective X-ray magnetic circular dichroic signals. The robust antiferromagnetic coupling is stabilized by a superexchange interaction, driven by the out-of-plane molecular orbitals responsible of the magnetic ground state and electronically decoupled from the underlying metal via the graphene layer, as confirmed by ab initio theoretical predictions. These archetypal spin interfaces can be prototypes to demonstrate how antiferromagnetic and/or ferromagnetic coupling can be optimized by selecting the molecular orbital symmetry.
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Affiliation(s)
- Giulia Avvisati
- Dipartimento di Fisica , Università di Roma "La Sapienza" , I-00185 Roma , Italy
| | - Claudia Cardoso
- Centro S3 , CNR-Istituto Nanoscienze , I-41125 Modena , Italy
| | - Daniele Varsano
- Centro S3 , CNR-Istituto Nanoscienze , I-41125 Modena , Italy
| | - Andrea Ferretti
- Centro S3 , CNR-Istituto Nanoscienze , I-41125 Modena , Italy
| | - Pierluigi Gargiani
- ALBA Synchrotron Light Source, E-08290 Cerdanyola del Valles, Barcelona , Spain
| | - Maria Grazia Betti
- Dipartimento di Fisica , Università di Roma "La Sapienza" , I-00185 Roma , Italy
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