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Kuznetsova V, Coogan Á, Botov D, Gromova Y, Ushakova EV, Gun'ko YK. Expanding the Horizons of Machine Learning in Nanomaterials to Chiral Nanostructures. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2308912. [PMID: 38241607 PMCID: PMC11167410 DOI: 10.1002/adma.202308912] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Revised: 01/10/2024] [Indexed: 01/21/2024]
Abstract
Machine learning holds significant research potential in the field of nanotechnology, enabling nanomaterial structure and property predictions, facilitating materials design and discovery, and reducing the need for time-consuming and labor-intensive experiments and simulations. In contrast to their achiral counterparts, the application of machine learning for chiral nanomaterials is still in its infancy, with a limited number of publications to date. This is despite the great potential of machine learning to advance the development of new sustainable chiral materials with high values of optical activity, circularly polarized luminescence, and enantioselectivity, as well as for the analysis of structural chirality by electron microscopy. In this review, an analysis of machine learning methods used for studying achiral nanomaterials is provided, subsequently offering guidance on adapting and extending this work to chiral nanomaterials. An overview of chiral nanomaterials within the framework of synthesis-structure-property-application relationships is presented and insights on how to leverage machine learning for the study of these highly complex relationships are provided. Some key recent publications are reviewed and discussed on the application of machine learning for chiral nanomaterials. Finally, the review captures the key achievements, ongoing challenges, and the prospective outlook for this very important research field.
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Affiliation(s)
- Vera Kuznetsova
- School of Chemistry, CRANN and AMBER Research Centres, Trinity College Dublin, College Green, Dublin, D02 PN40, Ireland
| | - Áine Coogan
- School of Chemistry, CRANN and AMBER Research Centres, Trinity College Dublin, College Green, Dublin, D02 PN40, Ireland
| | - Dmitry Botov
- Everypixel Media Innovation Group, 021 Fillmore St., PMB 15, San Francisco, CA, 94115, USA
- Neapolis University Pafos, 2 Danais Avenue, Pafos, 8042, Cyprus
| | - Yulia Gromova
- Department of Molecular and Cellular Biology, Harvard University, 52 Oxford St., Cambridge, MA, 02138, USA
| | - Elena V Ushakova
- Department of Materials Science and Engineering, and Centre for Functional Photonics (CFP), City University of Hong Kong, Hong Kong SAR, 999077, P. R. China
| | - Yurii K Gun'ko
- School of Chemistry, CRANN and AMBER Research Centres, Trinity College Dublin, College Green, Dublin, D02 PN40, Ireland
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Liu Y, Nagaosa N. Current-Induced Creation of Topological Vortex Rings in a Magnetic Nanocylinder. PHYSICAL REVIEW LETTERS 2024; 132:126701. [PMID: 38579209 DOI: 10.1103/physrevlett.132.126701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2023] [Revised: 01/22/2024] [Accepted: 01/29/2024] [Indexed: 04/07/2024]
Abstract
Vortex rings are ubiquitous topological structures in nature. In solid magnetic systems, their formation leads to intriguing physical phenomena and potential device applications. However, realizing these topological magnetic vortex rings and manipulating their topology on demand have still been challenging. Here, we theoretically show that topological vortex rings can be created by a current pulse in a chiral magnetic nanocylinder with a trench structure. The creation process involves the formation of a vortex ring street, i.e., a chain of magnetic vortex rings with an alternative linking manner. The created vortex rings can be bounded with monopole-antimonopole pairs and possess a rich and controllable linking topology (e.g., Hopf link and Solomon link), which is determined by the duration and amplitude of the current pulse. Our proposal paves the way for the realization and manipulation of diverse three-dimensional (3D) topological spin textures and could catalyze the development of 3D spintronic devices.
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Affiliation(s)
- Yizhou Liu
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan
| | - Naoto Nagaosa
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan
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Zheng F, Kiselev NS, Rybakov FN, Yang L, Shi W, Blügel S, Dunin-Borkowski RE. Hopfion rings in a cubic chiral magnet. Nature 2023; 623:718-723. [PMID: 37993571 PMCID: PMC10665190 DOI: 10.1038/s41586-023-06658-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2023] [Accepted: 09/20/2023] [Indexed: 11/24/2023]
Abstract
Magnetic skyrmions and hopfions are topological solitons1-well-localized field configurations that have gained considerable attention over the past decade owing to their unique particle-like properties, which make them promising objects for spintronic applications. Skyrmions2,3 are two-dimensional solitons resembling vortex-like string structures that can penetrate an entire sample. Hopfions4-9 are three-dimensional solitons confined within a magnetic sample volume and can be considered as closed twisted skyrmion strings that take the shape of a ring in the simplest case. Despite extensive research on magnetic skyrmions, the direct observation of magnetic hopfions is challenging10 and has only been reported in a synthetic material11. Here we present direct observations of hopfions in crystals. In our experiment, we use transmission electron microscopy to observe hopfions forming coupled states with skyrmion strings in B20-type FeGe plates. We provide a protocol for nucleating such hopfion rings, which we verify using Lorentz imaging and electron holography. Our results are highly reproducible and in full agreement with micromagnetic simulations. We provide a unified skyrmion-hopfion homotopy classification and offer insight into the diversity of topological solitons in three-dimensional chiral magnets.
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Affiliation(s)
- Fengshan Zheng
- Spin-X Institute, Electron Microscopy Center, School of Physics and Optoelectronics, State Key Laboratory of Luminescent Materials and Devices, Guangdong-Hong Kong-Macao Joint Laboratory of Optoelectronic and Magnetic Functional Materials, South China University of Technology, Guangzhou, China.
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, Forschungszentrum Jülich, Jülich, Germany.
- Peter Grünberg Institute, Forschungszentrum Jülich, Jülich, Germany.
| | - Nikolai S Kiselev
- Peter Grünberg Institute, Forschungszentrum Jülich, Jülich, Germany.
- Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, Jülich, Germany.
| | - Filipp N Rybakov
- Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden.
| | - Luyan Yang
- Institute of Microstructure and Properties of Advanced Materials, Faculty of Materials and Manufacturing, Beijing University of Technology, Beijing, China
| | - Wen Shi
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, Forschungszentrum Jülich, Jülich, Germany
- Peter Grünberg Institute, Forschungszentrum Jülich, Jülich, Germany
| | - Stefan Blügel
- Peter Grünberg Institute, Forschungszentrum Jülich, Jülich, Germany
- Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, Jülich, Germany
| | - Rafal E Dunin-Borkowski
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, Forschungszentrum Jülich, Jülich, Germany
- Peter Grünberg Institute, Forschungszentrum Jülich, Jülich, Germany
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Okumura S, Kravchuk VP, Garst M. Instability of Magnetic Skyrmion Strings Induced by Longitudinal Spin Currents. PHYSICAL REVIEW LETTERS 2023; 131:066702. [PMID: 37625063 DOI: 10.1103/physrevlett.131.066702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Revised: 06/13/2023] [Accepted: 07/11/2023] [Indexed: 08/27/2023]
Abstract
It is well established that spin-transfer torques exerted by in-plane spin currents give rise to a motion of magnetic skyrmions resulting in a skyrmion Hall effect. In films of finite thickness or in three-dimensional bulk samples the skyrmions extend in the third direction forming a string. We demonstrate that a spin current flowing longitudinally along the skyrmion string instead induces a Goldstone spin wave instability. Our analytical results are confirmed by micromagnetic simulations of both a single string as well as string lattices, suggesting that the instability eventually breaks the strings. A longitudinal current is thus able to melt the skyrmion string lattice via a nonequilibrium phase transition. For films of finite thickness or in the presence of disorder a threshold current will be required, and we estimate the latter assuming weak collective pinning.
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Affiliation(s)
- Shun Okumura
- Department of Applied Physics, the University of Tokyo, Tokyo 113-8656, Japan
| | - Volodymyr P Kravchuk
- Institut für Theoretische Festkörperphysik, Karlsruher Institut für Technologie, D-76131 Karlsruhe, Germany
- Bogolyubov Institute for Theoretical Physics of National Academy of Sciences of Ukraine, 03143 Kyiv, Ukraine
| | - Markus Garst
- Institut für Theoretische Festkörperphysik, Karlsruher Institut für Technologie, D-76131 Karlsruhe, Germany
- Institute for Quantum Materials and Technology, Karlsruhe Institute of Technology, D-76131 Karlsruhe, Germany
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Castillo-Sepúlveda S, Corona RM, Saavedra E, Laroze D, Espejo AP, Carvalho-Santos VL, Altbir D. Nucleation and Stability of Toron Chains in Non-Centrosymmetric Magnetic Nanowires. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:1816. [PMID: 37368246 DOI: 10.3390/nano13121816] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Revised: 05/29/2023] [Accepted: 06/05/2023] [Indexed: 06/28/2023]
Abstract
This work analyzes the magnetic configurations of cylindrical nanowires with a bulk Dzyaloshinskii-Moriya interaction and easy-plane anisotropy. We show that this system allows the nucleation of a metastable toron chain even when no out-of-plane anisotropy exists in the nanowire's top and bottom surfaces, as usually required. The number of nucleated torons depends on the nanowire length and the strength of an external magnetic field applied to the system. The size of each toron depends on the fundamental magnetic interactions and can be controlled by external stimuli, allowing the use of these magnetic textures as information carriers or nano-oscillator elements. Our results evidence that the topology and structure of the torons yield a wide variety of behaviors, revealing the complex nature of these topological textures, which should present an exciting interaction dynamic, depending on the initial conditions.
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Affiliation(s)
- Sebastián Castillo-Sepúlveda
- Grupo de Investigación en Física Aplicada, Facultad de Ingeniería, Universidad Autónoma de Chile, Avenida Pedro de Valdivia 425, Providencia 7500912, Chile
| | - Rosa M Corona
- Departamento de Física, CEDENNA, Universidad de Santiago de Chile, Avenida Víctor Jara 3493, Estación Central, Santiago 9170022, Chile
| | - Eduardo Saavedra
- Department of Physics, University of Santiago de Chile (USACH), Santiago 9170124, Chile
| | - David Laroze
- Instituto de Alta Investigación, Universidad de Tarapacá, Casilla 7D, Arica 1000000, Chile
| | - Alvaro P Espejo
- Departamento de Física, CEDENNA, Universidad de Santiago de Chile, Avenida Víctor Jara 3493, Estación Central, Santiago 9170022, Chile
| | - Vagson L Carvalho-Santos
- Departamento de Física, Universidade Federal de Viçosa, Avenida Peter Henry Rolfs s/n, Viçosa 36570-000, MG, Brazil
| | - Dora Altbir
- Departamento de Física, CEDENNA, Universidad de Santiago de Chile, Avenida Víctor Jara 3493, Estación Central, Santiago 9170022, Chile
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