1
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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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2
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Melchakova IA, Oyeniyi GT, Polyutov SP, Avramov PV. Spin Polarization and Flat Bands in Eu-Doped Nanoporous and Twisted Bilayer Graphenes. MICROMACHINES 2023; 14:1889. [PMID: 37893326 PMCID: PMC10609095 DOI: 10.3390/mi14101889] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2023] [Revised: 09/25/2023] [Accepted: 09/28/2023] [Indexed: 10/29/2023]
Abstract
Advanced two-dimensional spin-polarized heterostructures based on twisted (TBG) and nanoporous (NPBG) bilayer graphenes doped with Eu ions were theoretically proposed and studied using Periodic Boundary Conditions Density Functional theory electronic structure calculations. The significant polarization of the electronic states at the Fermi level was discovered for both Eu/NPBG(AA) and Eu/TBG lattices. Eu ions' chemi- and physisorption to both graphenes may lead to structural deformations, drop of symmetry of low-dimensional lattices, interlayer fusion, and mutual slides of TBG graphene fragments. The frontier bands in the valence region at the vicinity of the Fermi level of both spin-polarized 2D Eu/NPBG(AA) and Eu/TBG lattices clearly demonstrate flat dispersion laws caused by localized electronic states formed by TBG Moiré patterns, which could lead to strong electron correlations and the formation of exotic quantum phases.
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Affiliation(s)
- Iu. A. Melchakova
- School of Physics and Engineering, ITMO University, 197101 St. Petersburg, Russia;
| | - G. T. Oyeniyi
- Department of Chemistry, Kyungpook National University, Daegu 41566, Republic of Korea;
| | - S. P. Polyutov
- International Research Center of Spectroscopy and Quantum Chemistry (IRC SQC), Siberian Federal University, Svobodniy pr. 79/10, 600041 Krasnoyarsk, Russia;
| | - P. V. Avramov
- Department of Chemistry, Kyungpook National University, Daegu 41566, Republic of Korea;
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3
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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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4
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Kats VN, Shelukhin LA, Usachev PA, Averyanov DV, Karateev IA, Parfenov OE, Taldenkov AN, Tokmachev AM, Storchak VG, Pavlov VV. Femtosecond optical orientation triggering magnetization precession in epitaxial EuO films. NANOSCALE 2023; 15:2828-2836. [PMID: 36688382 DOI: 10.1039/d2nr04872h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Light-induced magnetization response unfolding on a temporal scale down to femtoseconds presents a way to convey information via spin manipulation. The advancement of the field requires exploration of new materials implementing various mechanisms for ultrafast magnetization dynamics. Here, pump-probe measurements of EuO-based ferromagnets by a time-resolved two-colour stroboscopic technique are reported. Epitaxial films of the pristine semiconductor and metallic Gd-doped EuO demonstrate photo-induced magnetization precession. Comparative experimental studies of both systems are carried out varying temperature, magnetic field, and polarization light helicity of the pump beam, followed by numerical estimates. The study establishes optical spin orientation by the electronic transition 4f75d0 → 4f65d1 as a mechanism triggering collective magnetization precession in these materials. The results suggest applications of EuO-based systems in optoelectronics and spintronics.
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Affiliation(s)
| | | | | | - Dmitry V Averyanov
- 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 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.
| | - 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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5
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Rybkin AG, Tarasov AV, Rybkina AA, Usachov DY, Petukhov AE, Eryzhenkov AV, Pudikov DA, Gogina AA, Klimovskikh II, Di Santo G, Petaccia L, Varykhalov A, Shikin AM. Sublattice Ferrimagnetism in Quasifreestanding Graphene. PHYSICAL REVIEW LETTERS 2022; 129:226401. [PMID: 36493449 DOI: 10.1103/physrevlett.129.226401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2021] [Revised: 08/17/2022] [Accepted: 10/14/2022] [Indexed: 06/17/2023]
Abstract
We show that graphene can be magnetized by coupling to a ferromagnetic Co film through a Au monolayer. The presence of dislocation loops under graphene leads to a ferrimagnetic ordering of moments in the two C sublattices. It is shown that the band gap of ∼80 meV in the K[over ¯] point has a magnetic nature and exists for ferrimagnetic ordering. Interplay between Rashba and exchange couplings is evidenced by spin splitting asymmetry in spin-ARPES measurements and fully supported by DFT calculation of a (9×9) unit cell. Owing to sign-opposite Berry curvatures for K[over ¯] and K[over ¯]^{'} valleys, the synthesized system is promising for the realization of a circular dichroism Hall effect.
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Affiliation(s)
- Artem G Rybkin
- St. Petersburg State University, 198504 St. Petersburg, Russia
| | - Artem V Tarasov
- St. Petersburg State University, 198504 St. Petersburg, Russia
| | - Anna A Rybkina
- St. Petersburg State University, 198504 St. Petersburg, Russia
| | | | | | | | | | | | - Ilya I Klimovskikh
- St. Petersburg State University, 198504 St. Petersburg, Russia
- Center for Advanced Mesoscience and Nanotechnology, Moscow Institute of Physics and Technology, 141700 Dolgoprudny, Russia
| | - Giovanni Di Santo
- Elettra Sincrotrone Trieste, Strada Statale 14 km 163.5, 34149 Trieste, Italy
| | - Luca Petaccia
- Elettra Sincrotrone Trieste, Strada Statale 14 km 163.5, 34149 Trieste, Italy
| | - Andrei Varykhalov
- Helmholtz-Zentrum Berlin für Materialien und Energie, Elektronenspeicherring BESSY II, Albert-Einstein-Str. 15, D-12489 Berlin, Germany
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6
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Averyanov DV, Sokolov IS, Taldenkov AN, Parfenov OE, Tokmachev AM, Storchak VG. 2D magnetic phases of Eu on Ge(110). NANOSCALE 2022; 14:12377-12385. [PMID: 35972030 DOI: 10.1039/d2nr02777a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
2D magnetic materials are at the forefront of research on fundamentals of magnetism; they exhibit unconventional phases and properties controlled by external stimuli. 2D magnets offer a solution to the problem of miniaturization of spintronic devices. A technological target of materials science is to find suitable magnetic materials and scale their thickness down as much as possible, a single monolayer being a natural limit. However, magnetism does not halt at one monolayer - it may persist beyond this boundary, to sparse but regular lattices of magnetic atoms. Here, we report 2D magnetic phases of Eu on the Ge(110) surface. We synthesized two submonolayer structures Eu/Ge(110) employing molecular beam epitaxy. The phases, identified by electron diffraction, differ in the surface density of Eu atoms. At low temperature, they exhibit magnetic ordering with magnetic moments lying in-plane. Strong dependence of the effective magnetic transition temperature on weak magnetic fields points at the 2D nature of the observed magnetism. The results are set against those on the Eu/Si system. The study of Eu/Ge(110) magnets demonstrates that a variety of substrates of different structure and symmetry can host submonolayer 2D magnetic phases, suggesting the phenomenon to be rather general.
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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.
| | - 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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7
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Verchenko VY, Kanibolotskiy AV, Bogach AV, Znamenkov KO, Shevelkov AV. Ferromagnetic correlations in the layered van der Waals sulfide FeAl 2S 4. Dalton Trans 2022; 51:8454-8460. [PMID: 35593508 DOI: 10.1039/d2dt00671e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Transition metal-based layered compounds with van der Waals gaps between the adjacent layers are a source of two-dimensional (2D) nanomaterials with nontrivial transport and magnetic properties. 2D ferromagnets, both metals and semiconductors, can be leveraged to produce spin-polarized current in spintronic devices with tailored functionalities. Here, we report on the synthesis, crystal growth, crystal and electronic structure, and magnetic properties of the Fe-based FeAl2S4 layered sulfide. In the crystal structure, Fe and Al atoms mix on octahedral and tetrahedral sites between hexagonal layers of S atoms, which are terminated by the van der Waals gaps. Band structure calculations reveal strong electronic correlations within the semiconducting ground state, which induce ferromagnetism with the magnetic moment of 0.12μB per formula unit for a Hubbard interaction U = 5 eV and Hund's rule coupling J = 0.8 eV. Crystal growth employing chemical vapor transport reactions results in bulk cleavable crystals, which show paramagnetic Curie-Weiss behavior at high temperatures with the Fe2+ magnetic centers. At low temperatures, an anomaly is observed on the magnetic susceptibility curve, below which the magnetization shows ferromagnetic hysteresis, indicating the presence of ferromagnetic correlations in FeAl2S4.
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Affiliation(s)
- Valeriy Yu Verchenko
- Department of Chemistry, Lomonosov Moscow State University, 119991 Moscow, Russia. .,National Institute of Chemical Physics and Biophysics, 12618 Tallinn, Estonia
| | | | - Alexey V Bogach
- Prokhorov General Physics Institute of the Russian Academy of Sciences, 119991 Moscow, Russia
| | | | - Andrei V Shevelkov
- Department of Chemistry, Lomonosov Moscow State University, 119991 Moscow, Russia.
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8
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Investigation of Phase Transitions in Ferromagnetic Nanofilms on a Non-Magnetic Substrate by Computer Simulation. MATERIALS 2022; 15:ma15072390. [PMID: 35407723 PMCID: PMC8999669 DOI: 10.3390/ma15072390] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Revised: 03/19/2022] [Accepted: 03/22/2022] [Indexed: 11/17/2022]
Abstract
Magnetic properties of ferromagnetic nanofilms on non-magnetic substrate are examined by computer simulation. The substrate influence is modeled using the two-dimensional Frenkel-Kontorova potential. The film has a cubic crystal lattice. Cases of different ratio for substrate period and ferromagnetic film period are considered. The difference in film and substrate periods results in film deformations. These deformations result in a change in the magnetic properties of the film. The Ising model and the Metropolis algorithm are used for the study of magnetic properties. The dependence of Curie temperature on film thickness and substrate potential parameters is calculated. Cases of different values for the coverage factor are considered. The deformation of the film layers is reduced away from the substrate when it is compressed or stretched. The Curie temperature increases when the substrate is compressed and decreases when the substrate is stretched. This pattern is performed for films with different thicknesses. If the coating coefficient for the film is different from one, periodic structures with an increased or reduced concentration of atoms are formed in the film first layer. These structures are absent in higher layers.
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9
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He K, Barut B, Yin S, Randle MD, Dixit R, Arabchigavkani N, Nathawat J, Mahmood A, Echtenkamp W, Binek C, Dowben PA, Bird JP. Graphene on Chromia: A System for Beyond-Room-Temperature Spintronics. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2105023. [PMID: 34986269 DOI: 10.1002/adma.202105023] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 12/23/2021] [Indexed: 06/14/2023]
Abstract
Evidence of robust spin-dependent transport in monolayer graphene, deposited on the (0001) surface of the antiferromagnetic (AFM)/magneto-electric oxide chromia (Cr2 O3 ), is provided. Measurements performed in the non-local spin-Hall geometry reveal a robust signal that is present at zero external magnetic field and which is significantly larger than any possible ohmic contribution. The spin-related signal persists well beyond the Néel temperature (≈307 K) that defines the transition between the AFM and paramagnetic states, remaining visible at the highest studied temperature of close to 450 K. This robust character is consistent with prior theoretical studies of the graphene/Cr2 O3 system, predicting that the lifting of sub-lattice symmetry in the graphene shall induce an effective spin-orbit term of ≈40 meV. Overall, the results indicate that graphene-on-chromia heterostructures are a highly promising framework for the implementation of spintronic devices, capable of operation well beyond room temperature.
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Affiliation(s)
- Keke He
- Department of Electrical Engineering, University at Buffalo, The State University of New York, Buffalo, New York, 14260, USA
| | - Bilal Barut
- Department of Electrical Engineering, University at Buffalo, The State University of New York, Buffalo, New York, 14260, USA
| | - Shenchu Yin
- Department of Electrical Engineering, University at Buffalo, The State University of New York, Buffalo, New York, 14260, USA
| | - Michael D Randle
- Department of Electrical Engineering, University at Buffalo, The State University of New York, Buffalo, New York, 14260, USA
| | - Ripudaman Dixit
- Department of Electrical Engineering, University at Buffalo, The State University of New York, Buffalo, New York, 14260, USA
| | - Nargess Arabchigavkani
- Department of Electrical Engineering, University at Buffalo, The State University of New York, Buffalo, New York, 14260, USA
| | - Jubin Nathawat
- Department of Electrical Engineering, University at Buffalo, The State University of New York, Buffalo, New York, 14260, USA
| | - Ather Mahmood
- Department of Physics and Astronomy, Theodore Jorgensen Hall, University of Nebraska Lincoln, Lincoln, Nebraska, 68588-0299, USA
| | - Will Echtenkamp
- Department of Physics and Astronomy, Theodore Jorgensen Hall, University of Nebraska Lincoln, Lincoln, Nebraska, 68588-0299, USA
| | - Christian Binek
- Department of Physics and Astronomy, Theodore Jorgensen Hall, University of Nebraska Lincoln, Lincoln, Nebraska, 68588-0299, USA
| | - Peter A Dowben
- Department of Physics and Astronomy, Theodore Jorgensen Hall, University of Nebraska Lincoln, Lincoln, Nebraska, 68588-0299, USA
| | - Jonathan P Bird
- Department of Electrical Engineering, University at Buffalo, The State University of New York, Buffalo, New York, 14260, USA
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10
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Tan H, Shan G, Pacchioni G. Prediction of 2D ferromagnetism and monovalent europium ions in EuBr/graphene heterojunctions. Phys Chem Chem Phys 2021; 23:25500-25506. [PMID: 34730141 DOI: 10.1039/d1cp02218k] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Europium, one of the rare-earth elements, exhibits +2 and +3 valence states and has been widely used for the magnetic modification of materials. Based on density functional theory calculations, we predicted 2D EuBr/graphene heterojunctions to exhibit metallicity, huge intrinsic-ferromagnetism nearly 7.0 μB per Eu and the special monovalent Eu ions. Electron localization function (ELF), difference charge densities and Bader charge analyses demonstrated that there are cation-π interactions between the EuBr films and graphene. Graphene works as a substrate to enable the stability of EuBr monolayer crystals, where EuBr plays an important role to yield ferromagnetism and enhance metallicity in the heterojunctions. Monte Carlo simulations were used to estimate a Curie temperature of about 7 K, which, together with magnetic configurations, can be further modulated by external strains and charge-carrier doping. In general, our theoretical work predicts the properties of novel 2D ferromagnetic EuBr/graphene heterojunctions, suggesting the possibility of combining 2D intrinsic-ferromagnetic metal halide crystals and graphene, and opening up a new perspective in next-generation electronic, spintronic devices and high-performance sensors.
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Affiliation(s)
- Haoyi Tan
- School of Instrumentation Science and Opto-electronics Engineering & Institute of Precision Instrument and Quantum Sensing, Beihang University, Beijing 100191, China.
| | - Guangcun Shan
- School of Instrumentation Science and Opto-electronics Engineering & Institute of Precision Instrument and Quantum Sensing, Beihang University, Beijing 100191, China. .,Department of Materials Science and Engineering, City University of Hong Kong, Kowloon Tong, Hong Kong SAR
| | - Gianfranco Pacchioni
- Dipartimento di Scienza dei Materiali, Università degli Studi Milano-Bicocca, 20125 Milano, Italy
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11
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Parfenov OE, Averyanov DV, Sokolov IS, Taldenkov AN, Karateev IA, Tokmachev AM, Storchak VG. High Carrier Mobility in a Layered Antiferromagnet Integrated with Silicon. ACS APPLIED MATERIALS & INTERFACES 2021; 13:41926-41932. [PMID: 34436853 DOI: 10.1021/acsami.1c13623] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Coupling various functional properties in one material is always a challenge, more so if the material should be nanostructured for practical applications. Magnetism and high carrier mobility are key components for spintronic applications but rather difficult to bundle together. Here, we establish EuAl2Si2 as a layered antiferromagnet supporting high carrier mobility. Its topotactic synthesis via a sacrificial two-dimensional template results in epitaxial nanoscale films on silicon. Their outstanding structural quality and atomically sharp interfaces are demonstrated by diffraction and microscopy techniques. EuAl2Si2 films exhibit extreme magnetoresistance and a carrier mobility of above 10,000 cm2 V-1 s-1. The marriage of these properties and magnetism makes EuAl2Si2 a promising spintronic material. Importantly, the seamless integration of EuAl2Si2 with silicon technology is particularly appealing for applications.
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Affiliation(s)
- Oleg E Parfenov
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, 123182 Moscow, Russia
| | - 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
| | - Igor A Karateev
- 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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12
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Aboljadayel ROM, Ionescu A, Burton OJ, Cheglakov G, Hofmann S, Barnes CHW. Growth and Characterisation Studies of Eu 3O 4 Thin Films Grown on Si/SiO 2 and Graphene. NANOMATERIALS (BASEL, SWITZERLAND) 2021; 11:1598. [PMID: 34204525 PMCID: PMC8233992 DOI: 10.3390/nano11061598] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Revised: 06/02/2021] [Accepted: 06/02/2021] [Indexed: 11/17/2022]
Abstract
We report the growth, structural and magnetic properties of the less studied Eu-oxide phase, Eu3O4, thin films grown on a Si/SiO2 substrate and Si/SiO2/graphene using molecular beam epitaxy. The X-ray diffraction scans show that highly textured crystalline Eu3O4(001) films are grown on both substrates, whereas the film deposited on graphene has a better crystallinity than that grown on the Si/SiO2 substrate. The SQUID measurements show that both films have a Curie temperature of ∼5.5±0.1 K, with a magnetic moment of ∼320 emu/cm3 at 2 K. The mixed valence of the Eu cations has been confirmed by the qualitative analysis of the depth-profile X-ray photoelectron spectroscopy measurements with the Eu2+:Eu3+ ratio of 28:72. However, surprisingly, our films show no metamagnetic behaviour as reported for the bulk and powder form. Furthermore, the microscopic optical images and Raman measurements show that the graphene underlayer remains largely intact after the growth of the Eu3O4 thin films.
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Affiliation(s)
- Razan O. M. Aboljadayel
- Cavendish Laboratory, Physics Department, University of Cambridge, Cambridge CB3 0HE, UK; (A.I.); (G.C.); (C.H.W.B.)
- Diamond Light Source, Didcot OX11 0DE, UK
| | - Adrian Ionescu
- Cavendish Laboratory, Physics Department, University of Cambridge, Cambridge CB3 0HE, UK; (A.I.); (G.C.); (C.H.W.B.)
| | - Oliver J. Burton
- Department of Engineering, University of Cambridge, Cambridge CB3 0FA, UK; (O.J.B.); (S.H.)
| | - Gleb Cheglakov
- Cavendish Laboratory, Physics Department, University of Cambridge, Cambridge CB3 0HE, UK; (A.I.); (G.C.); (C.H.W.B.)
| | - Stephan Hofmann
- Department of Engineering, University of Cambridge, Cambridge CB3 0FA, UK; (O.J.B.); (S.H.)
| | - Crispin H. W. Barnes
- Cavendish Laboratory, Physics Department, University of Cambridge, Cambridge CB3 0HE, UK; (A.I.); (G.C.); (C.H.W.B.)
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13
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Zhang C, Zhang S, Lin Y, Tao J, Guan L. Strong valley splitting in d0two-dimensional SnO induced by magnetic proximity effect. NANOTECHNOLOGY 2021; 32:225201. [PMID: 33618342 DOI: 10.1088/1361-6528/abe895] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Accepted: 02/22/2021] [Indexed: 06/12/2023]
Abstract
Strong magnetic interfacial coupling in van der Waals heterostructures is important for designing novel electronic devices. Besides the most studied transition metal dichalcogenides (TMDCs) materials, we demonstrate that the valley splitting can be activated in two-dimensional tetragonald0metal oxide, SnO, via the magnetic proximity effect by EuBrO. In SnO/EuBrO, the valley splitting of SnO can reach ∼46 meV, which is comparable to many TMDCs and equivalent to an external magnetic field of 800 T. In addition, the valley splitting can be further enhanced by adjusting interlayer distance and applying uniaxial strains. A design principle of new spintronic device based on this unique electronic structure of SnO/EuBrO has been proposed. Our findings indicate that SnO is a promising material for future valleytronics applications.
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Affiliation(s)
- Changcheng Zhang
- School of Science, Hebei University of Technology, Tianjin, 300401, People's Republic of China
| | - Shuo Zhang
- School of Materials Science and Engineering, Hebei University of Technology, Tianjin, 300130, People's Republic of China
| | - Yifeng Lin
- School of Materials Science and Engineering, Hebei University of Technology, Tianjin, 300130, People's Republic of China
| | - Junguang Tao
- School of Materials Science and Engineering, Hebei University of Technology, Tianjin, 300130, People's Republic of China
| | - Lixiu Guan
- School of Science, Hebei University of Technology, Tianjin, 300401, People's Republic of China
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14
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Boukhvalov DW, Politano A. Unveiling the origin of room-temperature ferromagnetism in monolayer VSe 2: the role of extrinsic effects. NANOSCALE 2020; 12:20875-20882. [PMID: 33047776 DOI: 10.1039/d0nr04663a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Room-temperature ferromagnetism in monolayer vanadium diselenide (VSe2) on graphite is the object of a controversial debate. Herein, we unveil the contribution from extrinsic factors to the magnetic properties of monolayer VSe2 by means of density functional theory. Specifically, we demonstrate that either intrinsic defects or the adsorption of molecules enhances ferromagnetic interactions. The expansion of the VSe2 lattice increases the magnetic moment on vanadium ions, whereas both compression and out-of-plane distortion withdraw magnetic moments. The exchange interactions between vanadium ions and magnetic defects (vacancies and impurities) in the surface and subsurface layers of the substrate are able to turn the unstable two-dimensional (2D) ferromagnetism into stable three-dimensional (3D) ferromagnetism. Definitely, the combination of effects related to chemisorption, substrate-induced distortion and magnetic defects of the substrate could enhance or suppress ferromagnetism in monolayer VSe2.
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Affiliation(s)
- Danil W Boukhvalov
- College of Science, Institute of Materials Physics and Chemistry, Nanjing Forestry University, Nanjing 210037, P. R. China. and Institute of Physics and Technology, Ural Federal University, Mira Street 19, 620002 Yekaterinburg, Russia
| | - Antonio Politano
- Department of Physical and Chemical Sciences, University of L'Aquila, via Vetoio, 67100 L'Aquila, AQ, Italy and CNR-IMM Istituto per la Microelettronica e Microsistemi, VIII strada 5, I-95121 Catania, Italy
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15
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Mariscal-Jiménez A, Tarazaga Martín-Luengo A, Galiana B, Ballesteros C, Bonanni A, Martín-Sánchez J, Serna R. Photoluminescence and Stoichiometry Correlation in Nanocrystalline EuO x Thin Films: Tunable Color Emission. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2020; 124:15434-15439. [PMID: 32704340 PMCID: PMC7370298 DOI: 10.1021/acs.jpcc.0c03052] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Revised: 06/02/2020] [Indexed: 06/11/2023]
Abstract
The development of broadband and ultracompact optoelectronic devices relies on the possibility of fabricating bright and tunable emitters at the nanoscale. Here, we show emission from EuO x (1 ≤ x < 1.4) thin films on silicon formed by nanocrystals with average sizes in the range of 5 nm. The photoluminescence emission of the nano-EuO x films is tunable as a function of the oxygen concentration changing from a green broadband Eu2+-related emission to a narrow red Eu3+-related emission. To reach these results has been instrumental through the use of a new methodology specially designed to achieve high-quality europium oxide films whose compositional properties are controlled by the growth base pressure and preserved thanks to a chemically stable and transparent cover layer of Al2O3. Our findings confirm the outstanding potential of nanostructured EuO x films as "one-compound" optical elements with tunable emission properties for their implementation in integrated silicon-based devices.
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Affiliation(s)
- Antonio Mariscal-Jiménez
- Laser
Processing Group, Instituto de Óptica,
IO-CSIC, C/Serrano 121, 28006 Madrid, Spain
- Departamento
de Tecnologías de la Información, Escuela Politécnica
Superior, Universidad CEU-San Pablo, CEU
Universities, Campus Montepríncipe, Boadilla del Monte, Madrid 28668, Spain
| | | | - Beatriz Galiana
- Department
of Physics, Escuela Politécnica Superior, Universidad Carlos III, 28911 Leganés, Madrid, Spain
| | - Carmen Ballesteros
- Department
of Physics, Escuela Politécnica Superior, Universidad Carlos III, 28911 Leganés, Madrid, Spain
| | - Alberta Bonanni
- Institut
für Halbleiter-und-Festkörperphysik, Johannes Kepler University, Altenbergerstr. 69, A-4040 Linz, Austria
| | - Javier Martín-Sánchez
- Institut
für Halbleiter-und-Festkörperphysik, Johannes Kepler University, Altenbergerstr. 69, A-4040 Linz, Austria
- Departamento
de Física, Universidad de Oviedo, 33007 Oviedo, Spain
- Center of
Research on Nanomaterials and Nanotechnology, CINN (CSIC−Universidad de Oviedo), El Entrego 33940, Spain
| | - Rosalía Serna
- Laser
Processing Group, Instituto de Óptica,
IO-CSIC, C/Serrano 121, 28006 Madrid, Spain
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16
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Shukla V. Observation of critical magnetic behavior in 2D carbon based composites. NANOSCALE ADVANCES 2020; 2:962-990. [PMID: 36133050 PMCID: PMC9418615 DOI: 10.1039/c9na00663j] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2019] [Accepted: 01/08/2020] [Indexed: 05/30/2023]
Abstract
Two dimensional (2D) carbonaceous materials such as graphene and its derivatives, e.g., graphdiyne, have enormous potential possibilities in major fields of scientific research. Theoretically, it has been proposed that the perfect atomic lattice arrangement of these materials is responsible for their outstanding physical and chemical properties, and also for their poor magnetic properties. Experimentally, it is difficult to obtain a perfect atomic lattice of carbon atoms due to the appearance of structural disorder. This structural disorder is generated during the growth or synthesis of carbon-related materials. Investigations of structural disorder reveal that it can offer both advantages and disadvantages depending on the application. For instance, disorder reduces the thermal and mechanical stability, and deteriorates the performance of 2D carbon-based electronic devices. The most interesting effect of structural disorder can be seen in the field of magnetism. Disorder not only creates magnetic ordering within 2D carbon materials but also influences the local electronic structure, which opens the door for future spintronic devices. Although various studies on the disorder induced magnetism of 2D carbon materials are available in the literature, some parts of the above field have still not been fully exploited. This review presents existing work for the future development of 2D carbon-based devices.
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Affiliation(s)
- Vineeta Shukla
- Nuclear Condensed Matter Physics Laboratory, Department of Physics, Indian Institute of Technology Kharagpur-721302 India
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17
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Song G, Ranjbar M, Daughton DR, Kiehl RA. Nanoparticle-Induced Anomalous Hall Effect in Graphene. NANO LETTERS 2019; 19:7112-7118. [PMID: 31513412 DOI: 10.1021/acs.nanolett.9b02643] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Schemes for introducing magnetic properties into graphene are of fundamental interest and could enable the development of electrically controlled magnetic devices, thereby extending graphene's applications from conventional electronics to spintronics. Proximity-induced ferromagnetism (PIFM) has been reported for graphene coupled to adjacent ferromagnetic insulators (FMIs). PIFM from an FMI preserves graphene's high carrier mobility and does not introduce a parallel current path. However, few FMIs other than yttrium-iron-garnet are suitable for practical applications due to difficulties in their growth and deposition and to their typically low Curie temperatures. Furthermore, it is difficult to obtain a high-quality FMI/graphene interface by graphene transfer methods, which are essential for obtaining the required interfacial exchange coupling. Here, we report the observation of the anomalous Hall effect (AHE) in graphene proximity coupled to an array of magnetic nanoparticles. This observation of AHE in graphene in proximity to a discontinuous magnetic structure opens the door to realizing magnetic properties in graphene from a greatly expanded range of materials and offers new possibilities for realizing patterned spintronic devices and circuitry.
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Affiliation(s)
- Guibin Song
- School of Electrical, Computer and Energy Engineering , Arizona State University , Tempe , Arizona 85287 , United States
| | - Mojtaba Ranjbar
- School of Electrical, Computer and Energy Engineering , Arizona State University , Tempe , Arizona 85287 , United States
| | - David R Daughton
- Lake Shore Cryotronics , Westerville , Ohio 43082 , United States
| | - Richard A Kiehl
- School of Electrical, Computer and Energy Engineering , Arizona State University , Tempe , Arizona 85287 , United States
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18
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Pushkarev GV, Mazurenko VG, Mazurenko VV, Boukhvalov DW. Structural phase transitions in VSe2: energetics, electronic structure and magnetism. Phys Chem Chem Phys 2019; 21:22647-22653. [DOI: 10.1039/c9cp03726h] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
First principles calculations of the magnetic and electronic properties of VSe2 describing the transition between two structural phases (H,T) were performed.
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Affiliation(s)
| | | | | | - Danil W. Boukhvalov
- College of Science
- Institute of Materials Physics and Chemistry
- Nanjing Forestry University
- Nanjing 210037
- P. R. China
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19
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Nie K, Wang X, Mi W. Magnetic proximity effect induced spin-dependent electronic structure in two-dimensional SnO by half-metallic monolayer CrN ferromagnet. Phys Chem Chem Phys 2019; 21:6984-6990. [DOI: 10.1039/c9cp00690g] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The electronic structure and magnetic anisotropy of a 2D SnO/CrN heterostructure can be tailored by strains and interlayer distances.
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Affiliation(s)
- Kai Nie
- Tianjin Key Laboratory of Film Electronic & Communicate Devices
- School of Electrical and Electronic Engineering
- Tianjin University of Technology
- Tianjin 300384
- China
| | - Xiaocha Wang
- Tianjin Key Laboratory of Film Electronic & Communicate Devices
- School of Electrical and Electronic Engineering
- Tianjin University of Technology
- Tianjin 300384
- China
| | - Wenbo Mi
- Tianjin Key Laboratory of Low Dimensional Materials Physics and Preparation Technology
- School of Science
- Tianjin University
- Tianjin 300354
- China
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20
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Parfenov OE, Averyanov DV, Tokmachev AM, Karateev IA, Taldenkov AN, Kondratev OA, Storchak VG. Interface-Induced Anomalous Hall Conductivity in a Confined Metal. ACS APPLIED MATERIALS & INTERFACES 2018; 10:35589-35598. [PMID: 30247015 DOI: 10.1021/acsami.8b10962] [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
The mature silicon technological platform is actively explored for spintronic applications. Metal silicides are an integral part of the Si technology used as interconnects, gate electrodes, and diffusion barriers; their epitaxial integration with Si results in premier contacts. Recent studies highlight the exceptional role of electronic discontinuities at interfaces in the spin-dependent transport properties. Here, we report a new type of Hall conductivity driven by sharp interfaces of Eu silicide, an antiferromagnetic metal, sandwiched between two insulators - Si and SiO x. Quasi-ballistic transport probes spin-orbit coupling at the interfaces, in particular, charge-spin interconversion. Transverse magnetic field results in anomalous Hall effect signals of an unusual line shape. The interplay between opposite-sign signals from the two interfaces allows efficient control over the magnitude and sign of the overall effect. Selective engineering of interfaces singles out a particular spin signal. The two-channel nature of the effect and its high tunability offer new functional possibilities for future spintronic devices.
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Affiliation(s)
- Oleg E Parfenov
- 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
| | - Andrey M Tokmachev
- 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
| | - Alexander N Taldenkov
- 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
| | - Vyacheslav G Storchak
- National Research Center "Kurchatov Institute" , Kurchatov Sq. 1 , Moscow 123182 , Russia
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