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Averyanov DV, Sokolov IS, Taldenkov AN, Parfenov OE, Larionov KV, Sorokin PB, Kondratev OA, Tokmachev AM, Storchak VG. Engineering of a Layered Ferromagnet via Graphitization: An Overlooked Polymorph of GdAlSi. J Am Chem Soc 2024; 146:15761-15770. [PMID: 38825888 DOI: 10.1021/jacs.4c01472] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2024]
Abstract
Layered magnets are stand-out materials because of their range of functional properties that can be controlled by external stimuli. Regretfully, the class of such compounds is rather narrow, prompting the search for new members. Graphitization─stabilization of layered graphitic structures in the 2D limit─is being discussed for cubic materials. We suggest the phenomenon to extend beyond cubic structures; it can be employed as a viable route to a variety of layered materials. Here, the idea of graphitization is put into practice to produce a new layered magnet, GdAlSi. The honeycomb material, based on graphene-like layers AlSi, is studied both experimentally and theoretically. Epitaxial films of GdAlSi are synthesized on silicon; the critical thickness for the stability of the layered polymorph is around 20 monolayers. Notably, the layered polymorph of GdAlSi demonstrates ferromagnetism, in contrast to the nonlayered, tetragonal polymorph. The ferromagnetism is further supported by electron transport measurements revealing negative magnetoresistance and the anomalous Hall effect. The results show that graphitization can be a powerful tool in the design of functional layered materials.
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Affiliation(s)
- Dmitry V Averyanov
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, 123182 Moscow, Russia
| | - Ivan S Sokolov
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, 123182 Moscow, Russia
| | - Alexander N Taldenkov
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, 123182 Moscow, Russia
| | - Oleg E Parfenov
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, 123182 Moscow, Russia
| | - Konstantin V Larionov
- Laboratory of Digital Materials Science, National University of Science and Technology MISIS, Leninskiy prospect 4, 119049 Moscow, Russia
| | - Pavel B Sorokin
- Laboratory of Digital Materials Science, National University of Science and Technology MISIS, Leninskiy prospect 4, 119049 Moscow, Russia
| | - Oleg A Kondratev
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, 123182 Moscow, Russia
| | - Andrey M Tokmachev
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, 123182 Moscow, Russia
| | - Vyacheslav G Storchak
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, 123182 Moscow, Russia
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2
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Mattiat H, Schneider L, Reiser P, Poggio M, Sahafi P, Jordan A, Budakian R, Averyanov DV, Sokolov IS, Taldenkov AN, Parfenov OE, Kondratev OA, Tokmachev AM, Storchak VG. Mapping the phase-separated state in a 2D magnet. NANOSCALE 2024; 16:5302-5312. [PMID: 38372414 DOI: 10.1039/d3nr06550b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2024]
Abstract
Intrinsic 2D magnets have recently been established as a playground for studies on fundamentals of magnetism, quantum phases, and spintronic applications. The inherent instability at low dimensionality often results in coexistence and/or competition of different magnetic orders. Such instability of magnetic ordering may manifest itself as phase-separated states. In 4f 2D materials, magnetic phase separation is expressed in various experiments; however, the experimental evidence is circumstantial. Here, we employ a high-sensitivity MFM technique to probe the spatial distribution of magnetic states in the paradigmatic 4f 2D ferromagnet EuGe2. Below the ferromagnetic transition temperature, we discover the phase-separated state and follow its evolution with temperature and magnetic field. The characteristic length-scale of magnetic domains amounts to hundreds of nanometers. These observations strongly shape our understanding of the magnetic states in 2D materials at the monolayer limit and contribute to engineering of ultra-compact spintronics.
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Affiliation(s)
- Hinrich Mattiat
- Department of Physics & Swiss Nanoscience Institute, University of Basel, 4056 Basel, Switzerland.
| | - Lukas Schneider
- Department of Physics & Swiss Nanoscience Institute, University of Basel, 4056 Basel, Switzerland.
| | - Patrick Reiser
- Department of Physics & Swiss Nanoscience Institute, University of Basel, 4056 Basel, Switzerland.
| | - Martino Poggio
- Department of Physics & Swiss Nanoscience Institute, University of Basel, 4056 Basel, Switzerland.
| | - Pardis Sahafi
- Department of Physics and Astronomy & Institute for Quantum Computing, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Andrew Jordan
- Department of Physics and Astronomy & Institute for Quantum Computing, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Raffi Budakian
- Department of Physics and Astronomy & Institute for Quantum Computing, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Dmitry V Averyanov
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, 123182 Moscow, Russia.
| | - Ivan S Sokolov
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, 123182 Moscow, Russia.
| | - Alexander N Taldenkov
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, 123182 Moscow, Russia.
| | - Oleg E Parfenov
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, 123182 Moscow, Russia.
| | - Oleg A Kondratev
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, 123182 Moscow, Russia.
| | - Andrey M Tokmachev
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, 123182 Moscow, Russia.
| | - Vyacheslav G Storchak
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, 123182 Moscow, Russia.
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Averyanov DV, Sokolov IS, Taldenkov AN, Parfenov OE, Karateev IA, Kondratev OA, Tokmachev AM, Storchak VG. Intrinsic exchange bias state in silicene and germanene materials EuX 2. NANOSCALE HORIZONS 2023; 8:803-811. [PMID: 36987577 DOI: 10.1039/d3nh00009e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
2D magnets have recently emerged as a host for unconventional phases and related phenomena. The prominence of 2D magnetism stems from its high amenability to external stimuli and structural variations. The low dimensionality facilitates competition between magnetic orders which may give rise to exchange bias, in particular in magnetic heterostructures. Here, we propose a strategy for the search of exchange bias state in 2D individual compounds. We track the evolution of magnetic orders driven by the number of monolayers in a system exhibiting antiferromagnetism in the multilayer and ferromagnetism in the monolayer limit. The material, EuSi2, has the structure of multilayer silicene intercalated by Eu. A strong intrinsic exchange bias effect accompanies the dimensional crossover. Comparison with silicene-based GdSi2 and germanene-based EuGe2 suggests the competition between magnetic orders to be a common property of this class of materials that may be useful in spintronic applications.
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Affiliation(s)
- Dmitry V Averyanov
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, Moscow 123182, Russia.
| | - Ivan S Sokolov
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, Moscow 123182, Russia.
| | - Alexander N Taldenkov
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, Moscow 123182, Russia.
| | - Oleg E Parfenov
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, Moscow 123182, Russia.
| | - Igor A Karateev
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, Moscow 123182, Russia.
| | - Oleg A Kondratev
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, Moscow 123182, Russia.
| | - Andrey M Tokmachev
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, Moscow 123182, Russia.
| | - Vyacheslav G Storchak
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, Moscow 123182, Russia.
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4
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Noah A, Zur Y, Fridman N, Singh S, Gutfreund A, Herrera E, Vakahi A, Remennik S, Huber ME, Gazit S, Suderow H, Steinberg H, Millo O, Anahory Y. Nano-Patterned Magnetic Edges in CrGeTe 3 for Quasi 1-D Spintronic Devices. ACS APPLIED NANO MATERIALS 2023; 6:8627-8634. [PMID: 37256091 PMCID: PMC10226043 DOI: 10.1021/acsanm.3c01008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Accepted: 04/24/2023] [Indexed: 06/01/2023]
Abstract
The synthesis of two-dimensional van der Waals magnets has paved the way for both technological applications and fundamental research on magnetism confined to ultra-small length scales. Edge magnetic moments in ferromagnets are expected to be less magnetized than in the sample interior because of the reduced amount of neighboring ferromagnetic spins at the sample edge. We recently demonstrated that CrGeTe3 (CGT) flakes thinner than 10 nm are hard ferromagnets; i.e., they exhibit an open hysteresis loop. In contrast, thicker flakes exhibit zero net remnant field in the interior, with hard ferromagnetism present only at the cleaved edges. This experimental observation suggests that a nontrivial interaction exists between the sample edge and the interior. Here, we demonstrate that artificial edges fabricated by focus ion beam etching also display hard ferromagnetism. This enables us to write magnetic nanowires in CGT directly and use this method to characterize the magnetic interaction between the interior and edge. The results indicate that the interior saturation and depolarization fields depend on the lateral dimensions of the sample. Most notably, the interior region between the edges of a sample narrower than 300 nm becomes a hard ferromagnet, suggesting an enhancement of the magnetic exchange induced by the proximity of the edges. Last, we find that the CGT regions amorphized by the gallium beam are nonmagnetic, which introduces a novel method to tune the local magnetic properties of CGT films, potentially enabling integration into spintronic devices.
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Affiliation(s)
- Avia Noah
- The Racah Institute of Physics, The Hebrew University, Jerusalem 9190401, Israel
| | - Yishay Zur
- The Racah Institute of Physics, The Hebrew University, Jerusalem 9190401, Israel
| | - Nofar Fridman
- The Racah Institute of Physics, The Hebrew University, Jerusalem 9190401, Israel
| | - Sourabh Singh
- The Racah Institute of Physics, The Hebrew University, Jerusalem 9190401, Israel
| | - Alon Gutfreund
- The Racah Institute of Physics, The Hebrew University, Jerusalem 9190401, Israel
| | - Edwin Herrera
- Laboratorio de Bajas Temperaturas, Unidad Asociada UAM/CSIC, Departamento de Física de la Materia Condensada, Instituto Nicolás Cabrera and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, E-28049 Madrid, Spain
| | - Atzmon Vakahi
- Center for Nanoscience and Nanotechnology, Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Sergei Remennik
- Center for Nanoscience and Nanotechnology, Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Martin Emile Huber
- Departments of Physics and Electrical Engineering, University of Colorado Denver, Denver, Colorado 80217, United States
| | - Snir Gazit
- The Racah Institute of Physics, The Hebrew University, Jerusalem 9190401, Israel
- The Fritz Haber Research Center for Molecular Dynamics, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Hermann Suderow
- Laboratorio de Bajas Temperaturas, Unidad Asociada UAM/CSIC, Departamento de Física de la Materia Condensada, Instituto Nicolás Cabrera and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, E-28049 Madrid, Spain
| | - Hadar Steinberg
- The Racah Institute of Physics, The Hebrew University, Jerusalem 9190401, Israel
| | - Oded Millo
- The Racah Institute of Physics, The Hebrew University, Jerusalem 9190401, Israel
| | - Yonathan Anahory
- The Racah Institute of Physics, The Hebrew University, Jerusalem 9190401, Israel
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5
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Sokolov IS, Averyanov DV, Parfenov OE, Taldenkov AN, Rybin MG, Tokmachev AM, Storchak VG. Proximity Coupling of Graphene to a Submonolayer 2D Magnet. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2023:e2301295. [PMID: 36971277 DOI: 10.1002/smll.202301295] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 02/27/2023] [Indexed: 06/18/2023]
Abstract
Imprinting magnetism into graphene may lead to unconventional electron states and enable the design of spin logic devices with low power consumption. The ongoing active development of 2D magnets suggests their coupling with graphene to induce spin-dependent properties via proximity effects. In particular, the recent discovery of submonolayer 2D magnets on surfaces of industrial semiconductors provides an opportunity to magnetize graphene coupled with silicon. Here, synthesis and characterization of large-area graphene/Eu/Si(001) heterostructures combining graphene with a submonolayer magnetic superstructure of Eu on silicon are reported. Eu intercalation at the interface of the graphene/Si(001) system results in a Eu superstructure different from those formed on pristine Si in terms of symmetry. The resulting system graphene/Eu/Si(001) exhibits 2D magnetism with the transition temperature controlled by low magnetic fields. Negative magnetoresistance and the anomalous Hall effect in the graphene layer provide evidence for spin polarization of the carriers. Most importantly, the graphene/Eu/Si system seeds a class of graphene heterostructures based on submonolayer magnets aiming at applications in graphene spintronics.
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Affiliation(s)
- Ivan S Sokolov
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, Moscow, 123182, Russia
| | - Dmitry V Averyanov
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, Moscow, 123182, Russia
| | - Oleg E Parfenov
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, Moscow, 123182, Russia
| | - Alexander N Taldenkov
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, Moscow, 123182, Russia
| | - Maxim G Rybin
- Prokhorov General Physics Institute of the Russian Academy of Sciences, 38 Vavilov St., Moscow, 119991, Russia
| | - Andrey M Tokmachev
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, Moscow, 123182, Russia
| | - Vyacheslav G Storchak
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, Moscow, 123182, Russia
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