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Optical manipulation of magnetic vortices visualized in situ by Lorentz electron microscopy

Understanding the fundamental dynamics of topological vortex and antivortex naturally formed in microscale/nanoscale ferromagnetic building blocks under external perturbations is crucial to magnetic vortex–based information processing and spintronic devices. All previous studies have focused on magn...

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Autores principales: Fu, Xuewen, Pollard, Shawn D., Chen, Bin, Yoo, Byung-Kuk, Yang, Hyunsoo, Zhu, Yimei
Formato: Online Artículo Texto
Lenguaje:English
Publicado: American Association for the Advancement of Science 2018
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6054509/
https://www.ncbi.nlm.nih.gov/pubmed/30035226
http://dx.doi.org/10.1126/sciadv.aat3077
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author Fu, Xuewen
Pollard, Shawn D.
Chen, Bin
Yoo, Byung-Kuk
Yang, Hyunsoo
Zhu, Yimei
author_facet Fu, Xuewen
Pollard, Shawn D.
Chen, Bin
Yoo, Byung-Kuk
Yang, Hyunsoo
Zhu, Yimei
author_sort Fu, Xuewen
collection PubMed
description Understanding the fundamental dynamics of topological vortex and antivortex naturally formed in microscale/nanoscale ferromagnetic building blocks under external perturbations is crucial to magnetic vortex–based information processing and spintronic devices. All previous studies have focused on magnetic vortex–core switching via external magnetic fields, spin-polarized currents, or spin waves, which have largely prohibited the investigation of novel spin configurations that could emerge from the ground states in ferromagnetic disks and their underlying dynamics. We report in situ visualization of femtosecond laser quenching–induced magnetic vortex changes in various symmetric ferromagnetic Permalloy disks by using Lorentz phase imaging of four-dimensional electron microscopy that enables in situ laser excitation. Besides the switching of magnetic vortex chirality and polarity, we observed with distinct occurrence frequencies a plenitude of complex magnetic structures that have never been observed by magnetic field– or current-assisted switching. These complex magnetic structures consist of a number of newly created topological magnetic defects (vortex and antivortex) strictly conserving the topological winding number, demonstrating the direct impact of topological invariants on magnetization dynamics in ferromagnetic disks. Their spin configurations show mirror or rotation symmetry due to the geometrical confinement of the disks. Combined micromagnetic simulations with the experimental observations reveal the underlying magnetization dynamics and formation mechanism of the optical quenching–induced complex magnetic structures. Their distinct occurrence rates are pertinent to their formation-growth energetics and pinning effects at the disk edge. On the basis of these findings, we propose a paradigm of optical quenching–assisted fast switching of vortex cores for the control of magnetic vortex–based information recording and spintronic devices.
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spelling pubmed-60545092018-07-22 Optical manipulation of magnetic vortices visualized in situ by Lorentz electron microscopy Fu, Xuewen Pollard, Shawn D. Chen, Bin Yoo, Byung-Kuk Yang, Hyunsoo Zhu, Yimei Sci Adv Research Articles Understanding the fundamental dynamics of topological vortex and antivortex naturally formed in microscale/nanoscale ferromagnetic building blocks under external perturbations is crucial to magnetic vortex–based information processing and spintronic devices. All previous studies have focused on magnetic vortex–core switching via external magnetic fields, spin-polarized currents, or spin waves, which have largely prohibited the investigation of novel spin configurations that could emerge from the ground states in ferromagnetic disks and their underlying dynamics. We report in situ visualization of femtosecond laser quenching–induced magnetic vortex changes in various symmetric ferromagnetic Permalloy disks by using Lorentz phase imaging of four-dimensional electron microscopy that enables in situ laser excitation. Besides the switching of magnetic vortex chirality and polarity, we observed with distinct occurrence frequencies a plenitude of complex magnetic structures that have never been observed by magnetic field– or current-assisted switching. These complex magnetic structures consist of a number of newly created topological magnetic defects (vortex and antivortex) strictly conserving the topological winding number, demonstrating the direct impact of topological invariants on magnetization dynamics in ferromagnetic disks. Their spin configurations show mirror or rotation symmetry due to the geometrical confinement of the disks. Combined micromagnetic simulations with the experimental observations reveal the underlying magnetization dynamics and formation mechanism of the optical quenching–induced complex magnetic structures. Their distinct occurrence rates are pertinent to their formation-growth energetics and pinning effects at the disk edge. On the basis of these findings, we propose a paradigm of optical quenching–assisted fast switching of vortex cores for the control of magnetic vortex–based information recording and spintronic devices. American Association for the Advancement of Science 2018-07-20 /pmc/articles/PMC6054509/ /pubmed/30035226 http://dx.doi.org/10.1126/sciadv.aat3077 Text en Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC). http://creativecommons.org/licenses/by-nc/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial license (http://creativecommons.org/licenses/by-nc/4.0/) , which permits use, distribution, and reproduction in any medium, so long as the resultant use is not for commercial advantage and provided the original work is properly cited.
spellingShingle Research Articles
Fu, Xuewen
Pollard, Shawn D.
Chen, Bin
Yoo, Byung-Kuk
Yang, Hyunsoo
Zhu, Yimei
Optical manipulation of magnetic vortices visualized in situ by Lorentz electron microscopy
title Optical manipulation of magnetic vortices visualized in situ by Lorentz electron microscopy
title_full Optical manipulation of magnetic vortices visualized in situ by Lorentz electron microscopy
title_fullStr Optical manipulation of magnetic vortices visualized in situ by Lorentz electron microscopy
title_full_unstemmed Optical manipulation of magnetic vortices visualized in situ by Lorentz electron microscopy
title_short Optical manipulation of magnetic vortices visualized in situ by Lorentz electron microscopy
title_sort optical manipulation of magnetic vortices visualized in situ by lorentz electron microscopy
topic Research Articles
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6054509/
https://www.ncbi.nlm.nih.gov/pubmed/30035226
http://dx.doi.org/10.1126/sciadv.aat3077
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