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Lewis GR, Wolf D, Lubk A, Ringe E, Midgley PA. WRAP: A wavelet-regularised reconstruction algorithm for magnetic vector electron tomography. Ultramicroscopy 2023; 253:113804. [PMID: 37481909 DOI: 10.1016/j.ultramic.2023.113804] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Revised: 06/09/2023] [Accepted: 06/30/2023] [Indexed: 07/25/2023]
Abstract
Magnetic vector electron tomography (VET) is a promising technique that enables better understanding of micro- and nano-magnetic phenomena through the reconstruction of 3D magnetic fields at high spatial resolution. Here we introduce WRAP (Wavelet Regularised A Program), a reconstruction algorithm for magnetic VET that directly reconstructs the magnetic vector potential A using a compressed sensing framework which regularises for sparsity in the wavelet domain. We demonstrate that using WRAP leads to a significant increase in the fidelity of the 3D reconstruction and is especially robust when dealing with very limited data; using datasets simulated with realistic noise, we compare WRAP to a conventional reconstruction algorithm and find an improvement of ca. 60% when averaged over several performance metrics. Moreover, we further validate WRAP's performance on experimental electron holography data, revealing the detailed magnetism of vortex states in a CuCo nanowire. We believe WRAP represents a major step forward in the development of magnetic VET as a tool for probing magnetism at the nanoscale.
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Affiliation(s)
- George R Lewis
- Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB3 0FS, UK; Department of Earth Sciences, University of Cambridge, Cambridge, CB2 3EQ, UK
| | - Daniel Wolf
- Institute for Solid State Research, IFW Dresden, Helmholtzstrasse 20, 01069, Dresden, Germany
| | - Axel Lubk
- Institute for Solid State Research, IFW Dresden, Helmholtzstrasse 20, 01069, Dresden, Germany; Institute of Solid State and Materials Physics, TU Dresden, 01062 Dresden, Germany
| | - Emilie Ringe
- Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB3 0FS, UK; Department of Earth Sciences, University of Cambridge, Cambridge, CB2 3EQ, UK
| | - Paul A Midgley
- Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB3 0FS, UK
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2
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Yu X, Liu Y, Iakoubovskii KV, Nakajima K, Kanazawa N, Nagaosa N, Tokura Y. Realization and Current-Driven Dynamics of Fractional Hopfions and Their Ensembles in a Helimagnet FeGe. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2210646. [PMID: 36871172 DOI: 10.1002/adma.202210646] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Revised: 02/19/2023] [Indexed: 05/19/2023]
Abstract
3D topological spin textures-hopfions-are predicted in helimagnetic systems but are not experimentally confirmed thus far. By utilizing an external magnetic field and electric current in the present study, 3D topological spin textures are realized, including fractional hopfions with nonzero topological index, in a skyrmion-hosting helimagnet FeGe. Microsecond current pulses are employed to control the dynamics of the expansion and contraction of a bundle composed of a skyrmion and a fractional hopfion, as well as its current-driven Hall motion. This research approach has demonstrated the novel electromagnetic properties of fractional hopfions and their ensembles in helimagnetic systems.
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Affiliation(s)
- Xiuzhen Yu
- RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan
| | - Yizhou Liu
- RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan
| | | | - Kiyomi Nakajima
- RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan
| | - Naoya Kanazawa
- Department of Applied Physics, University of Tokyo, Tokyo, 113-8656, Japan
| | - Naoto Nagaosa
- RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan
- Department of Applied Physics, University of Tokyo, Tokyo, 113-8656, Japan
| | - Yoshinori Tokura
- RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan
- Department of Applied Physics, University of Tokyo, Tokyo, 113-8656, Japan
- Tokyo College, University of Tokyo, Tokyo, 113-8656, Japan
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3
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Mitome M. Transport of intensity equation method and its applications. Microscopy (Oxf) 2021; 70:69-74. [PMID: 33524150 DOI: 10.1093/jmicro/dfaa053] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Revised: 09/03/2020] [Accepted: 09/08/2020] [Indexed: 11/14/2022] Open
Abstract
A phase retrieval technique based on a transport of intensity equation (TIE) is one of the defocus series reconstruction techniques in microscopy. Since it does not require any dedicated devices like a biprism, and only three defocus images are enough to retrieve phase information, it has been applied to observe magnetic fields, magnetic domains, electrostatic potentials and strains. It is also used to improve image resolution by correcting spherical aberration. This technique is simple and easy to use, but some artifacts often appear in the retrieved phase map. One should pay careful attention to the experimental conditions and the algorithms and boundary conditions used to solve the TIE. This paper reviews the principle of the TIE method, the algorithms used to solve it and application results in materials science.
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Affiliation(s)
- Masanori Mitome
- Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki Tsukuba Ibaraki, 305-0044, Japan
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4
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Campanini M, Nasi L, Fabbrici S, Casoli F, Celegato F, Barrera G, Chiesi V, Bedogni E, Magén C, Grillo V, Bertoni G, Righi L, Tiberto P, Albertini F. Magnetic Shape Memory Turns to Nano: Microstructure Controlled Actuation of Free-Standing Nanodisks. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2018; 14:e1803027. [PMID: 30294862 DOI: 10.1002/smll.201803027] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Revised: 09/12/2018] [Indexed: 06/08/2023]
Abstract
Magnetic shape memory materials hold a great promise for next-generation actuation devices and systems for energy conversion, thanks to the intimate coupling between structure and magnetism in their martensitic phase. Here novel magnetic shape memory free-standing nanodisks are proposed, proving that the lack of the substrate constrains enables the exploitation of new microstructure-controlled actuation mechanisms by the combined application of different stimuli-i.e., temperature and magnetic field. The results show that a reversible areal strain (up to 5.5%) can be achieved and tuned in intensity and sign (i.e., areal contraction or expansion) by the application of a magnetic field. The mechanisms at the basis of the actuation are investigated by experiments performed at different length scales and directly visualized by several electron microscopy techniques, including electron holography, showing that thermo/magnetomechanical properties can be optimized by engineering the martensitic microstructure through epitaxial growth and lateral confinement. These findings represent a step forward toward the development of a new class of temperature-field controlled nanoactuators and smart nanomaterials.
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Affiliation(s)
- Marco Campanini
- IMEM-CNR, Parco Area delle Scienze 37/A, 43124, Parma, Italy
- Empa, Ueberlandstrasse 129, 8600, Dübendorf, Switzerland
| | - Lucia Nasi
- IMEM-CNR, Parco Area delle Scienze 37/A, 43124, Parma, Italy
| | - Simone Fabbrici
- IMEM-CNR, Parco Area delle Scienze 37/A, 43124, Parma, Italy
- MIST E-R, via P. Gobetti 101, 40129, Bologna, Italy
| | | | | | | | | | - Elena Bedogni
- Dipartimento di Scienze Chimiche, Università di Parma, 43121, Parma, Italy
| | - César Magén
- ICMA, Universidad de Zaragoza-CSIC, 50009, Zaragoza, Spain
- LMA, Instituto de Nanociencia de Aragón, Universidad de Zaragoza, 50018, Zaragoza, Spain
| | - Vincenzo Grillo
- IMEM-CNR, Parco Area delle Scienze 37/A, 43124, Parma, Italy
- S3-CNR, Via Campi 213A, 41125, Modena, Italy
| | - Giovanni Bertoni
- IMEM-CNR, Parco Area delle Scienze 37/A, 43124, Parma, Italy
- Istituto Italiano di Tecnologia, Via Morego 30, 16163, Genova, Italy
| | - Lara Righi
- Dipartimento di Scienze Chimiche, Università di Parma, 43121, Parma, Italy
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Kashyap I, Jin YM, Vetter EP, Floro JA, De Graef M. Lorentz Transmission Electron Microscopy Image Simulations of Experimental Nano-Chessboard Observations in Co-Pt Alloys. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2018; 24:221-226. [PMID: 29855395 DOI: 10.1017/s143192761800034x] [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 magnetization configuration of a novel nano-chessboard structure consisting of L10 and L12 phases in a Co40Pt60 alloy is investigated using Lorentz transmission electron microscopy (LTEM) and micro-magnetic simulations. We show high-resolution LTEM images of nano-size magnetic features acquired through spherical aberration correction in Lorentz Fresnel mode. Phase reconstructions and LTEM image simulations are carried out to fully understand the magnetic microstructure. The experimental Fresnel images of the nano-chessboard structure show zig-zag shaped magnetic domain walls at the inter-phase boundaries between L10 and L12 phases. A circular magnetization distribution with vortex and anti-vortex type arrangement is evident in the phase reconstructed magnetic induction maps as well as simulated maps. The magnetic contrast in experimental LTEM images is interpreted with the help of magnetic induction maps simulated for various relative electron beam-sample orientations inside the TEM.
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Affiliation(s)
- Isha Kashyap
- 1Department of Materials Science and Engineering,Carnegie Mellon University,5000 Forbes Avenue,Pittsburgh,PA 15213,USA
| | - Yongmei M Jin
- 2Department of Materials Science and Engineering,Michigan Technological University,Houghton,MI 49931,USA
| | - Eric P Vetter
- 3Department of Materials Science and Engineering,University of Virginia,Charlottesville,VA 22903,USA
| | - Jerrold A Floro
- 3Department of Materials Science and Engineering,University of Virginia,Charlottesville,VA 22903,USA
| | - Marc De Graef
- 1Department of Materials Science and Engineering,Carnegie Mellon University,5000 Forbes Avenue,Pittsburgh,PA 15213,USA
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Prabhat K, Aditya Mohan K, Phatak C, Bouman C, De Graef M. 3D reconstruction of the magnetic vector potential using model based iterative reconstruction. Ultramicroscopy 2017; 182:131-144. [DOI: 10.1016/j.ultramic.2017.07.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2017] [Revised: 06/28/2017] [Accepted: 07/02/2017] [Indexed: 12/31/2022]
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7
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Eggebrecht T, Möller M, Gatzmann JG, Rubiano da Silva N, Feist A, Martens U, Ulrichs H, Münzenberg M, Ropers C, Schäfer S. Light-Induced Metastable Magnetic Texture Uncovered by in situ Lorentz Microscopy. PHYSICAL REVIEW LETTERS 2017; 118:097203. [PMID: 28306279 DOI: 10.1103/physrevlett.118.097203] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Indexed: 06/06/2023]
Abstract
Magnetic topological defects, such as vortices and Skyrmions, can be stabilized as equilibrium structures in nanoscale geometries and by tailored intrinsic magnetic interactions. Here, employing rapid quench conditions, we report the observation of a light-induced metastable magnetic texture, which consists of a dense nanoscale network of vortices and antivortices. Our results demonstrate the emergence of ordering mechanisms in quenched optically driven systems, which may give a general access to novel magnetic structures on nanometer length scales.
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Affiliation(s)
- Tim Eggebrecht
- I. Physical Institute, Georg-August-University, 37077 Göttingen, Germany
| | - Marcel Möller
- IV. Physical Institute, Georg-August-University, 37077 Göttingen, Germany
| | - J Gregor Gatzmann
- IV. Physical Institute, Georg-August-University, 37077 Göttingen, Germany
| | | | - Armin Feist
- IV. Physical Institute, Georg-August-University, 37077 Göttingen, Germany
| | - Ulrike Martens
- Institute of Physics, Ernst-Moritz-Arndt-University, 17489 Greifswald, Germany
| | - Henning Ulrichs
- I. Physical Institute, Georg-August-University, 37077 Göttingen, Germany
| | - Markus Münzenberg
- Institute of Physics, Ernst-Moritz-Arndt-University, 17489 Greifswald, Germany
| | - Claus Ropers
- IV. Physical Institute, Georg-August-University, 37077 Göttingen, Germany
| | - Sascha Schäfer
- IV. Physical Institute, Georg-August-University, 37077 Göttingen, Germany
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8
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Zweck J. Imaging of magnetic and electric fields by electron microscopy. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:403001. [PMID: 27536873 DOI: 10.1088/0953-8984/28/40/403001] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Nanostructured materials become more and more a part of our daily life, partly as self-assembled particles or artificially patterned. These nanostructures often possess intrinsic magnetic and/or electric fields which determine (at least partially) their physical properties. Therefore it is important to be able to measure these fields reliably on a nanometre scale. A rather common instrument for the investigation of these fields is the transmission electron microscope as it offers high spatial resolution. The use of an electron microscope to image electric and magnetic fields on a micron down to sub-nanometre scale is treated in detail for transmission electron microscopes (TEM) and scanning transmission electron microscopes (STEM). The formation of contrast is described for the most common imaging modes, the specific advantages and disadvantages of each technique are discussed and examples are given. In addition, the experimental requirements for the use of the techniques described are listed and explained.
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Affiliation(s)
- Josef Zweck
- Physics Faculty, University of Regensburg, Electron Microscopy Laboratory, 93040 Regensburg, Universitätsstrasse 31, Germany
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9
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Kohn A, Habibi A, Mayo M. Experimental evaluation of the 'transport-of-intensity' equation for magnetic phase reconstruction in Lorentz transmission electron microscopy. Ultramicroscopy 2015; 160:44-56. [PMID: 26452194 DOI: 10.1016/j.ultramic.2015.09.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Revised: 09/20/2015] [Accepted: 09/26/2015] [Indexed: 11/29/2022]
Abstract
The 'transport-of-intensity' equation (TIE) is a general phase reconstruction methodology that can be applied to Lorentz transmission electron microscopy (TEM) through the use of Fresnel-contrast (defocused) images. We present an experimental study to test the application of the TIE for quantitative magnetic mapping in Lorentz TEM without aberration correction by examining sub-micrometer sized Ni80Fe20 (Permalloy) elements. For a JEOL JEM 2100F adapted for Lorentz microscopy, we find that quantitative magnetic phase reconstructions are possible for defoci distances ranging between approximately 200 μm and 800 μm. The lower limit originates from competing sources of image intensity variations in Fresnel-contrast images, namely structural defects and diffraction contrast. The upper defocus limit is due to a numerical error in the estimation of the intensity derivative based on three images. For magnetic domains, we show quantitative reconstructions of the product of the magnetic induction vector and thickness in element sizes down to approximately 100 nm in lateral size and 5 nm thick resulting in a minimal detection of 5Tnm. Three types of magnetic structures are tested in terms of phase reconstruction: vortex cores, domain walls, and element edges. We quantify vortex core structures at a diameter of 12 nm while the structures of domain walls and element edges are characterized qualitatively. Finally, we show by image simulations that the conclusions of this experimental study are relevant to other Lorentz TEM in which spherical aberration and defocus are dominant aberrations.
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Affiliation(s)
- Amit Kohn
- Department of Materials Science and Engineering, Faculty of Engineering, Tel Aviv University, 69978 Tel Aviv, Israel.
| | - Avihay Habibi
- Department of Materials Engineering, Ben-Gurion University of the Negev, 84105 Beer Sheva, Israel
| | - Martin Mayo
- Department of Materials Engineering, Ben-Gurion University of the Negev, 84105 Beer Sheva, Israel
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10
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Zhang X, Oshima Y. Experimental evaluation of spatial resolution in phase maps retrieved by transport of intensity equation. Microscopy (Oxf) 2015; 64:395-400. [DOI: 10.1093/jmicro/dfv045] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2015] [Accepted: 07/24/2015] [Indexed: 11/14/2022] Open
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11
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Campanini M, Ciprian R, Bedogni E, Mega A, Chiesi V, Casoli F, de Julián Fernández C, Rotunno E, Rossi F, Secchi A, Bigi F, Salviati G, Magén C, Grillo V, Albertini F. Lorentz microscopy sheds light on the role of dipolar interactions in magnetic hyperthermia. NANOSCALE 2015; 7:7717-7725. [PMID: 25835488 DOI: 10.1039/c5nr00273g] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Monodispersed Fe3O4 nanoparticles with comparable size distributions have been synthesized by two different synthesis routes, co-precipitation and thermal decomposition. Thanks to the different steric stabilizations, the described samples can be considered as a model system to investigate the effects of magnetic dipolar interactions on the aggregation states of the nanoparticles. Moreover, the presence of magnetic dipolar interactions can strongly affect the nanoparticle efficiency as a hyperthermic mediator. In this paper, we present a novel way to visualize and map the magnetic dipolar interactions in different kinds of nanoparticle aggregates by the use of Lorentz microscopy, an easy and reliable in-line electron holographic technique. By exploiting Lorentz microscopy, which is complementary to the magnetic measurements, it is possible to correlate the interaction degrees of magnetic nanoparticles with their magnetic behaviors. In particular, we demonstrate that Lorentz microscopy is successful in visualizing the magnetic configurations stabilized by dipolar interactions, thus paving the way to the comprehension of the power loss mechanisms for different nanoparticle aggregates.
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Affiliation(s)
- M Campanini
- Istituto Materiali per l'Elettronica ed il Magnetismo IMEM-CNR, Parco Area delle Scienze 37/A, 43124 Parma, Italy.
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