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

Fu, Xuewen and Pollard, Shawn D. and Chen, Bin and Yoo, Byung-Kuk and Yang, Hyunsoo and Zhu, Yimei (2018) Optical manipulation of magnetic vortices visualized in situ by Lorentz electron microscopy. Science Advances, 4 (7). Art. No. eaat3077. ISSN 2375-2548. PMCID PMC6054509. https://resolver.caltech.edu/CaltechAUTHORS:20180720-145939161

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Abstract

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.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1126/sciadv.aat3077DOIArticle
http://advances.sciencemag.org/cgi/content/full/4/7/eaat3077/DC1PublisherSupporting Information
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6054509PubMed CentralArticle
ORCID:
AuthorORCID
Fu, Xuewen0000-0001-6116-4680
Yoo, Byung-Kuk0000-0002-2610-6685
Additional Information:© 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). Received for publication February 13, 2018. Accepted for publication June 4, 2018. We acknowledge Caltech for providing access to the 4D electron microscopy facility for this study. We thank J. S. Baskin for very helpful discussion and help on the Lorentz phase electron microscopy measurement with in situ femtosecond laser excitation. We also thank J. A. Garlow for fruitful discussion on the Lorentz phase imaging measurement. This work was supported by the Materials Science and Engineering Divisions, Office of Basic Energy Sciences of the U.S. Department of Energy under contract no. DESC0012704. Author contributions: Y.Z. and X.F. conceived the research project. X.F., B.C., and B.-K.Y. carried out the experimental measurements. S.D.P. prepared the samples. X.F. and S.D.P. performed data analysis with input from Y.Z. S.D.P. developed the model and performed the numerical simulations with input from H.Y. All the authors contributed to the discussion and the writing of the manuscript. The authors declare that they have no competing interests. Data and materials availability: All data needed to evaluate the conclusions in the paper are present in the paper and/or the Supplementary Materials. Additional data related to this paper may be requested from the authors.
Funders:
Funding AgencyGrant Number
Department of Energy (DOE)DE-SC0012704
Issue or Number:7
PubMed Central ID:PMC6054509
Record Number:CaltechAUTHORS:20180720-145939161
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20180720-145939161
Official Citation:Optical manipulation of magnetic vortices visualized in situ by Lorentz electron microscopy BY XUEWEN FU, SHAWN D. POLLARD, BIN CHEN, BYUNG-KUK YOO, HYUNSOO YANG, YIMEI ZHU Science Advances 20 Jul 2018: Vol. 4, no. 7, eaat3077 DOI: 10.1126/sciadv.aat3077
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:88090
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:23 Jul 2018 15:13
Last Modified:03 Oct 2019 20:03

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