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Ali H, Rusz J, Bürgler DE, Adam R, Schneider CM, Tai CW, Thersleff T. Noise-dependent bias in quantitative STEM-EMCD experiments revealed by bootstrapping. Ultramicroscopy 2024; 257:113891. [PMID: 38043363 DOI: 10.1016/j.ultramic.2023.113891] [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: 07/07/2023] [Revised: 11/13/2023] [Accepted: 11/23/2023] [Indexed: 12/05/2023]
Abstract
Electron magnetic circular dichroism (EMCD) is a powerful technique for estimating element-specific magnetic moments of materials on nanoscale with the potential to reach atomic resolution in transmission electron microscopes. However, the fundamentally weak EMCD signal strength complicates quantification of magnetic moments, as this requires very high precision, especially in the denominator of the sum rules. Here, we employ a statistical resampling technique known as bootstrapping to an experimental EMCD dataset to produce an empirical estimate of the noise-dependent error distribution resulting from application of EMCD sum rules to bcc iron in a 3-beam orientation. We observe clear experimental evidence that noisy EMCD signals preferentially bias the estimation of magnetic moments, further supporting this with error distributions produced by Monte-Carlo simulations. Finally, we propose guidelines for the recognition and minimization of this bias in the estimation of magnetic moments.
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Affiliation(s)
- Hasan Ali
- Department of Materials Science and Engineering, Uppsala University, Box 534, Uppsala 751 21, Sweden; Department of Materials and Environmental Chemistry, Stockholm University, Stockholm 106 91, Sweden; Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, Forschungszentrum Jülich, Jülich 52425, Germany.
| | - Jan Rusz
- Department of Physics and Astronomy, Uppsala University, Box 516, Uppsala 751 20, Sweden
| | - Daniel E Bürgler
- Peter Grünberg Institut, Forschungszentrum Jülich GmbH, Jülich D-52425, Germany
| | - Roman Adam
- Peter Grünberg Institut, Forschungszentrum Jülich GmbH, Jülich D-52425, Germany
| | - Claus M Schneider
- Peter Grünberg Institut, Forschungszentrum Jülich GmbH, Jülich D-52425, Germany
| | - Cheuk-Wai Tai
- Department of Materials and Environmental Chemistry, Stockholm University, Stockholm 106 91, Sweden
| | - Thomas Thersleff
- Department of Materials and Environmental Chemistry, Stockholm University, Stockholm 106 91, Sweden
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2
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Cui J, Sha H, Yang W, Yu R. Antiferromagnetic imaging via ptychographic phase retrieval. Sci Bull (Beijing) 2024; 69:466-472. [PMID: 38161093 DOI: 10.1016/j.scib.2023.12.044] [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: 10/20/2023] [Revised: 11/27/2023] [Accepted: 12/15/2023] [Indexed: 01/03/2024]
Abstract
Antiferromagnetic imaging is critical for understanding and optimizing the properties of antiferromagnetic materials and devices. Despite the widespread use of high-energy electrons for atomic-scale imaging, they have low sensitivity to spin textures. Typically, the magnetic contribution to the phase of a high-energy electron wave is weaker than one percent of the electrostatic potential. Here, we demonstrate direct imaging of antiferromagnetic lattice through precise phase retrieval via electron ptychography, paving the way for magnetic lattice imaging of antiferromagnetic materials and devices.
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Affiliation(s)
- Jizhe Cui
- School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China; MOE Key Laboratory of Advanced Materials, Tsinghua University, Beijing 100084, China; State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University, Beijing 100084, China
| | - Haozhi Sha
- School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China; MOE Key Laboratory of Advanced Materials, Tsinghua University, Beijing 100084, China; State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University, Beijing 100084, China
| | - Wenfeng Yang
- School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China; MOE Key Laboratory of Advanced Materials, Tsinghua University, Beijing 100084, China; State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University, Beijing 100084, China
| | - Rong Yu
- School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China; MOE Key Laboratory of Advanced Materials, Tsinghua University, Beijing 100084, China; State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University, Beijing 100084, China.
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3
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Zeng Z, Fu X, Hu Q, Liu G, Li J, Huang X. The influence of residual plural scattering after deconvolution in electron magnetic chiral dichroism. Ultramicroscopy 2023; 253:113806. [PMID: 37413857 DOI: 10.1016/j.ultramic.2023.113806] [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: 01/14/2023] [Revised: 06/21/2023] [Accepted: 06/30/2023] [Indexed: 07/08/2023]
Abstract
This work investigated the existence and influence of residual plural scattering in electron magnetic chiral dichroism (EMCD) spectra. A series of low-loss, conventional core-loss, and q-resolved core-loss spectra at Fe-L2,3 edges were detected from areas of different thicknesses in a plane-view sample of Fe/MgO (001) thin film. It reveals by comparison that there remains noticeable plural scattering in q-resolved spectra acquired at two particular chiral positions after deconvolution, and the residual scattering is more significant in thicker areas than thinner ones. Accordingly, the orbital-to-spin moment ratio extracted from EMCD spectra, which is the difference between the two q-resolved spectra after deconvolution, would be in principle increased with increasing sample thickness. The randomly fluctuated moment ratios displayed in our experiments are greatly attributed to a slight and irregular variation of local diffraction conditions due to the bending effect and imperfect epitaxy in detected areas. We suggest EMCD spectra should be acquired from sufficiently thin samples to minimize the plural scattering effect in originally detected spectra before any deconvolution. In addition, great care should be taken for slight misorientation and imperfect epitaxy when performing EMCD investigation on epitaxial thin films using a nano beam.
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Affiliation(s)
- Z Zeng
- International Joint Laboratory for Light Alloys (MOE), College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China
| | - X Fu
- International Joint Laboratory for Light Alloys (MOE), College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China; Shenyang National Laboratory for Materials Sciences, Chongqing University, Chongqing 400044, China.
| | - Q Hu
- International Joint Laboratory for Light Alloys (MOE), College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China
| | - G Liu
- International Joint Laboratory for Light Alloys (MOE), College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China
| | - J Li
- International Joint Laboratory for Light Alloys (MOE), College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China
| | - X Huang
- International Joint Laboratory for Light Alloys (MOE), College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China
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4
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Zhong X, Li Z. Atomic Structure and Electron Magnetic Circular Dichroism of Individual Rock Salt Structure Antiphase Boundaries in Spinel Ferrites. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2023; 29:373. [PMID: 37613028 DOI: 10.1093/micmic/ozad067.174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/25/2023]
Affiliation(s)
- Xiaoyan Zhong
- TRACE EM Unit and Department of Materials Science and Engineering, City University of Hong Kong, Kowloon, Hong Kong SAR, People's Republic of China
- City University of Hong Kong Matter Science Research Institute (Futian, Shenzhen), Shenzhen, People's Republic of China
- Nanomanufacturing Laboratory (NML), City University of Hong Kong Shenzhen Research Institute, Shenzhen, People's Republic of China
- Chengdu Research Institute, City University of Hong Kong, Chengdu, People's Republic of China
| | - Zhuo Li
- TRACE EM Unit and Department of Materials Science and Engineering, City University of Hong Kong, Kowloon, Hong Kong SAR, People's Republic of China
- City University of Hong Kong Matter Science Research Institute (Futian, Shenzhen), Shenzhen, People's Republic of China
- Nanomanufacturing Laboratory (NML), City University of Hong Kong Shenzhen Research Institute, Shenzhen, People's Republic of China
- Chengdu Research Institute, City University of Hong Kong, Chengdu, People's Republic of China
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5
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Ali H, Sathyanath SKM, Tai CW, Rusz J, Uusimaki T, Hjörvarsson B, Thersleff T, Leifer K. Single scan STEM-EMCD in 3-beam orientation using a quadruple aperture. Ultramicroscopy 2023; 251:113760. [PMID: 37285614 DOI: 10.1016/j.ultramic.2023.113760] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2022] [Revised: 03/06/2023] [Accepted: 05/13/2023] [Indexed: 06/09/2023]
Abstract
The need to acquire multiple angle-resolved electron energy loss spectra (EELS) is one of the several critical challenges associated with electron magnetic circular dichroism (EMCD) experiments. If the experiments are performed by scanning a nanometer to atomic-sized electron probe on a specific region of a sample, the precision of the local magnetic information extracted from such data highly depends on the accuracy of the spatial registration between multiple scans. For an EMCD experiment in a 3-beam orientation, this means that the same specimen area must be scanned four times while keeping all the experimental conditions same. This is a non-trivial task as there is a high chance of morphological and chemical modification as well as non-systematic local orientation variations of the crystal between the different scans due to beam damage, contamination and spatial drift. In this work, we employ a custom-made quadruple aperture to acquire the four EELS spectra needed for the EMCD analysis in a single electron beam scan, thus removing the above-mentioned complexities. We demonstrate a quantitative EMCD result for a beam convergence angle corresponding to sub-nm probe size and compare the EMCD results for different detector geometries.
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Affiliation(s)
- Hasan Ali
- Department of Materials and Environmental Chemistry, Stockholm University, 106 91 Stockholm, Sweden; Department of Materials Science and Engineering, Uppsala University, Box 534, 75121, Uppsala, Sweden.
| | | | - Cheuk-Wai Tai
- Department of Materials and Environmental Chemistry, Stockholm University, 106 91 Stockholm, Sweden
| | - Jan Rusz
- Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden
| | - Toni Uusimaki
- Department of Materials and Environmental Chemistry, Stockholm University, 106 91 Stockholm, Sweden
| | - Björgvin Hjörvarsson
- Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden
| | - Thomas Thersleff
- Department of Materials and Environmental Chemistry, Stockholm University, 106 91 Stockholm, Sweden
| | - Klaus Leifer
- Department of Materials Science and Engineering, Uppsala University, Box 534, 75121, Uppsala, Sweden
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6
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De Luca G, Spring J, Kaviani M, Jöhr S, Campanini M, Zakharova A, Guillemard C, Herrero-Martin J, Erni R, Piamonteze C, Rossell MD, Aschauer U, Gibert M. Top-Layer Engineering Reshapes Charge Transfer at Polar Oxide Interfaces. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2203071. [PMID: 35841137 DOI: 10.1002/adma.202203071] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Revised: 07/12/2022] [Indexed: 06/15/2023]
Abstract
Charge-transfer phenomena at heterointerfaces are a promising pathway to engineer functionalities absent in bulk materials but can also lead to degraded properties in ultrathin films. Mitigating such undesired effects with an interlayer reshapes the interface architecture, restricting its operability. Therefore, developing less-invasive methods to control charge transfer will be beneficial. Here, an appropriate top-interface design allows for remote manipulation of the charge configuration of the buried interface and concurrent restoration of the ferromagnetic trait of the whole film. Double-perovskite insulating ferromagnetic La2 NiMnO6 (LNMO) thin films grown on perovskite oxide substrates are investigated as a model system. An oxygen-vacancy-assisted electronic reconstruction takes place initially at the LNMO polar interfaces. As a result, the magnetic properties of 2-5 unit cell LNMO films are affected beyond dimensionality effects. The introduction of a top electron-acceptor layer redistributes the electron excess and restores the ferromagnetic properties of the ultrathin LNMO films. Such a strategy can be extended to other interfaces and provides an advanced approach to fine-tune the electronic features of complex multilayered heterostructures.
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Affiliation(s)
- Gabriele De Luca
- Department of Physics, University of Zurich, Winterthurerstrasse 190, Zurich, 8057, Switzerland
| | - Jonathan Spring
- Department of Physics, University of Zurich, Winterthurerstrasse 190, Zurich, 8057, Switzerland
| | - Moloud Kaviani
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, Bern, 3012, Switzerland
| | - Simon Jöhr
- Department of Physics, University of Zurich, Winterthurerstrasse 190, Zurich, 8057, Switzerland
| | - Marco Campanini
- Electron Microscopy Center, Empa, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, Dübendorf, 8600, Switzerland
| | - Anna Zakharova
- Swiss Light Source, Paul Scherrer Institut, Villigen, 5232, Switzerland
| | - Charles Guillemard
- ALBA Synchrotron Light Source, Carrer de la Llum 2-26, Cerdanyola del Vallès, 08290, Spain
| | - Javier Herrero-Martin
- ALBA Synchrotron Light Source, Carrer de la Llum 2-26, Cerdanyola del Vallès, 08290, Spain
| | - Rolf Erni
- Electron Microscopy Center, Empa, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, Dübendorf, 8600, Switzerland
| | | | - Marta D Rossell
- Electron Microscopy Center, Empa, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, Dübendorf, 8600, Switzerland
| | - Ulrich Aschauer
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, Bern, 3012, Switzerland
| | - Marta Gibert
- Department of Physics, University of Zurich, Winterthurerstrasse 190, Zurich, 8057, Switzerland
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7
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Song D, Zheng F, Dunin-Borkowski RE. Prospect for measuring two-dimensional van der Waals magnets by electron magnetic chiral dichroism. Ultramicroscopy 2022; 234:113476. [PMID: 35114564 DOI: 10.1016/j.ultramic.2022.113476] [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: 11/01/2021] [Revised: 01/13/2022] [Accepted: 01/24/2022] [Indexed: 10/19/2022]
Abstract
Two-dimensional (2D) van der Waals magnets have drawn considerable attention in recent years triggered by the huge interest in novel magnetism and spintronic devices. Magnetic measurement of 2D van der Waals (vdW) magnets is crucial to understand the physical origin of magnetism in 2D limits. Therefore, advanced magnetic characterization techniques are highly required. However, only a limited number of such techniques are available due to the extremely small volume of 2D vdW magnets. Here, we introduce the electron magnetic chiral dichroism (EMCD) technique in transmission electron microscope (TEM) to measure 2D vdW crystals. In comparison with some other already-employed techniques in 2D magnets, EMCD is able to quantitatively measure magnetic parameters in three orthogonal directions at nanometer or even at atomic scale. We then perform EMCD simulations on several typical 2D vdW magnets with respect to the accelerating voltage, the number of atomic layers and beam tilt under zone axial orientation. The intensity and distribution of EMCD signals in three orthogonal directions are given in the diffraction plane, thereby providing an optimized design to achieve EMCD measurements. Finally, we discuss the signal-to-noise-ratio and required electron dose in order to obtain a measurable EMCD signal for 2D vdW magnets. Our results provide a feasibility analysis and guideline to measure 2D vdW magnets in future experiments.
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Affiliation(s)
- Dongsheng Song
- Information Materials and Intelligent Sensing Laboratory of Anhui Province, Key Laboratory of Structure and Functional Regulation of Hybrid Materials of Ministry of Education, Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, China; Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungszentrum Jülich, Jülich 52425, Germany.
| | - Fengshan Zheng
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungszentrum Jülich, Jülich 52425, Germany
| | - Rafal E Dunin-Borkowski
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungszentrum Jülich, Jülich 52425, Germany
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8
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Sun M, Wang X, Guo X, Xu L, Kuang H, Xu C. Chirality at nanoscale for bioscience. Chem Sci 2022; 13:3069-3081. [PMID: 35414873 PMCID: PMC8926252 DOI: 10.1039/d1sc06378b] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Accepted: 02/08/2022] [Indexed: 12/17/2022] Open
Abstract
In the rapidly expanding fields of nanoscience and nanotechnology, there is considerable interest in chiral nanomaterials, which are endowed with unusually strong circular dichroism. In this review, we summarize the principles of organization underlying chiral nanomaterials and generalize the recent advances in the main strategies used to fabricate these nanoparticles for bioscience applications. The creation of chirality from nanoscale building blocks has been investigated both experimentally and theoretically, and the tunability of chirality using external fields, such as light and magnetic fields, has allowed the optical activity of these materials to be controlled and their properties understood. Therefore, the specific recognition and potential applications of chiral materials in bioscience are discussed. The effects of the chirality of nanostructures on biological systems have been exploited to sense and cut molecules, for therapeutic applications, and so on. In the final part of this review, we examine the future perspectives for chiral nanomaterials in bioscience and the challenges posed by them.
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Affiliation(s)
- Maozhong Sun
- International Joint Research Laboratory for Biointerface and Biodetection, State Key Lab of Food Science and Technology, School of Food Science and Technology, Jiangnan University Wuxi Jiangsu 214122 People's Republic of China
| | - Xiuxiu Wang
- International Joint Research Laboratory for Biointerface and Biodetection, State Key Lab of Food Science and Technology, School of Food Science and Technology, Jiangnan University Wuxi Jiangsu 214122 People's Republic of China
| | - Xiao Guo
- International Joint Research Laboratory for Biointerface and Biodetection, State Key Lab of Food Science and Technology, School of Food Science and Technology, Jiangnan University Wuxi Jiangsu 214122 People's Republic of China
| | - Liguang Xu
- International Joint Research Laboratory for Biointerface and Biodetection, State Key Lab of Food Science and Technology, School of Food Science and Technology, Jiangnan University Wuxi Jiangsu 214122 People's Republic of China
| | - Hua Kuang
- International Joint Research Laboratory for Biointerface and Biodetection, State Key Lab of Food Science and Technology, School of Food Science and Technology, Jiangnan University Wuxi Jiangsu 214122 People's Republic of China
| | - Chuanlai Xu
- International Joint Research Laboratory for Biointerface and Biodetection, State Key Lab of Food Science and Technology, School of Food Science and Technology, Jiangnan University Wuxi Jiangsu 214122 People's Republic of China
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9
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Maqbool Q, Jung A, Won S, Cho J, Son JG, Yeom B. Chiral Magneto-Optical Properties of Supra-Assembled Fe 3O 4 Nanoparticles. ACS APPLIED MATERIALS & INTERFACES 2021; 13:54301-54307. [PMID: 34748312 DOI: 10.1021/acsami.1c16954] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Research on the chiral magneto-optical properties of inorganic nanomaterials has enabled novel applications in advanced optical and electronic devices. However, the corresponding chiral magneto-optical responses have only been studied under strong magnetic fields of ≥1 T, which limits the wider application of these novel materials. In this paper, we report on the enhanced chiral magneto-optical activity of supra-assembled Fe3O4 magnetite nanoparticles in the visible range at weak magnetic fields of 1.5 mT. The spherical supra-assembled particles with a diameter of ∼90 nm prepared by solvothermal synthesis had single-crystal-like structures, which resulted from the oriented attachment of nanograins. They exhibited superparamagnetic behavior even with a relatively large supraparticle diameter that exceeded the size limit for superparamagnetism. This can be attributed to the small size of nanograins with a diameter of ∼12 nm that constitute the suprastructured particles. Magnetic circular dichroism (MCD) measurements at magnetic fields of 1.5 mT showed distinct chiral magneto-optical activity from charge transfer transitions of magnetite in the visible range. For the supraparticles with lower crystallinity, the MCD peaks in the 250-550 nm range assigned as the ligand-to-metal charge transfer (LMCT) and the inter-sublattice charge transfer (ISCT) show increased intensities in comparison to those with higher crystallinity samples. On the contrary, the higher crystallinity sample shows higher MCD intensities near 600-700 nm for the intervalence charge transfer (IVCT) transition. The differences in MCD responses can be attributed to the crystallinity determined by the reaction time, lattice distortion near grain boundaries of the constituent nanocrystals, and dipolar interactions in the supra-assembled structures.
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Affiliation(s)
- Qysar Maqbool
- Department of Chemical Engineering, Hanyang University, Seoul 04763, Republic of Korea
- Institute of Nano Science and Technology, Hanyang University, Seoul 04763, Republic of Korea
| | - Arum Jung
- Department of Chemical Engineering, Hanyang University, Seoul 04763, Republic of Korea
| | - Sojeong Won
- Department of Chemical Engineering, Hanyang University, Seoul 04763, Republic of Korea
| | - Jinhan Cho
- Department of Chemical and Biological Engineering, Korea University, Seongbuk-gu, Seoul 02841, Republic of Korea
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seongbuk-gu, Seoul 02841, Republic of Korea
| | - Jeong Gon Son
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seongbuk-gu, Seoul 02841, Republic of Korea
- Soft Hybrid Materials Research Center, Korea Institute of Science and Technology (KIST), Seongbuk-gu, Seoul 02792, Republic of Korea
| | - Bongjun Yeom
- Department of Chemical Engineering, Hanyang University, Seoul 04763, Republic of Korea
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10
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Song D, Dunin-Borkowski RE. Three-Dimensional Measurement of Magnetic Moment Vectors Using Electron Magnetic Chiral Dichroism at Atomic Scale. PHYSICAL REVIEW LETTERS 2021; 127:087202. [PMID: 34477412 DOI: 10.1103/physrevlett.127.087202] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Accepted: 07/29/2021] [Indexed: 06/13/2023]
Abstract
Here we have developed an approach of three-dimensional (3D) measurement of magnetic moment vectors in three Cartesian directions using electron magnetic chiral dichroism (EMCD) at atomic scale. Utilizing a subangstrom convergent electron beam in the scanning transmission electron microscopy (STEM), beam-position-dependent chiral electron energy-loss spectra (EELS), carrying the EMCD signals referring to magnetization in three Cartesian directions, can be obtained during the scanning across the atomic planes. The atomic resolution EMCD signals from all of three directions can be separately obtained simply by moving the EELS detector. Moreover, the EMCD signals can be remarkably enhanced using a defocused electron beam, relieving the issues of low signal intensity and signal-to-noise-ratio especially at atomic resolution. Our proposed method is compatible with the setup of the widely used atomic resolution STEM-EELS technique and provides a straightforward way to achieve 3D magnetic measurement at atomic scale on newly developing magnetic-field-free TEM.
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Affiliation(s)
- Dongsheng Song
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungszentrum Jülich, 52425 Jülich, Germany
- Information Materials and Intelligent Sensing Laboratory of Anhui Province, Key Laboratory of Structure and Functional Regulation of Hybrid Materials of Ministry of Education, Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, China
| | - Rafal E Dunin-Borkowski
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungszentrum Jülich, 52425 Jülich, Germany
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11
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Xie L, He D, He J. SnSe, the rising star thermoelectric material: a new paradigm in atomic blocks, building intriguing physical properties. MATERIALS HORIZONS 2021; 8:1847-1865. [PMID: 34846469 DOI: 10.1039/d1mh00091h] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Thermoelectric (TE) materials, which enable direct energy conversion between waste heat and electricity, have witnessed enormous and exciting developments over last several decades due to innovative breakthroughs both in materials and the synergistic optimization of structures and properties. Among the promising state-of-the-art materials for next-generation thermoelectrics, tin selenide (SnSe) has attracted rapidly growing research interest for its high TE performance and the intrinsic layered structure that leads to strong anisotropy. Moreover, complex interactions between lattice, charge, and orbital degrees of freedom in SnSe make up a large phase space for the optimization of its TE properties via the simultaneous tuning of structural and chemical features. Various techniques, especially advanced electron microscopy (AEM), have been devoted to exploring these critical multidiscipline correlations between TE properties and microstructures. In this review, we first focus on the intrinsic layered structure as well as the extrinsic structural "imperfectness" of various dimensions in SnSe as studied by AEM. Based on these characterization results, we give a comprehensive discussion on the current understanding of the structure-property relationship. We then point out the challenges and opportunities as provided by modern AEM techniques toward a deeper knowledge of SnSe based on electronic structures and lattice dynamics at the nanometer or even atomic scale, for example, the measurements of local charge and electric field distribution, phonon vibrations, bandgap, valence state, temperature, and resultant TE effects.
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Affiliation(s)
- Lin Xie
- Shenzhen Key Laboratory of Thermoelectric Materials and Department of Physics, Southern University of Science and Technology, Shenzhen, 518055, China.
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12
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Atomic-scale insights into quantum-order parameters in bismuth-doped iron garnet. Proc Natl Acad Sci U S A 2021; 118:2101106118. [PMID: 33975955 DOI: 10.1073/pnas.2101106118] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Bismuth and rare earth elements have been identified as effective substituent elements in the iron garnet structure, allowing an enhancement in magneto-optical response by several orders of magnitude in the visible and near-infrared region. Various mechanisms have been proposed to account for such enhancement, but testing of these ideas is hampered by a lack of suitable experimental data, where information is required not only regarding the lattice sites where substituent atoms are located but also how these atoms affect various order parameters. Here, we show for a Bi-substituted lutetium iron garnet how a suite of advanced electron microscopy techniques, combined with theoretical calculations, can be used to determine the interactions between a range of quantum-order parameters, including lattice, charge, spin, orbital, and crystal field splitting energy. In particular, we determine how the Bi distribution results in lattice distortions that are coupled with changes in electronic structure at certain lattice sites. These results reveal that these lattice distortions result in a decrease in the crystal-field splitting energies at Fe sites and in a lifted orbital degeneracy at octahedral sites, while the antiferromagnetic spin order remains preserved, thereby contributing to enhanced magneto-optical response in bismuth-substituted iron garnet. The combination of subangstrom imaging techniques and atomic-scale spectroscopy opens up possibilities for revealing insights into hidden coupling effects between multiple quantum-order parameters, thereby further guiding research and development for a wide range of complex functional materials.
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13
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Xu K, Gu Y, Song C, Zhong X, Zhu J. Atomic insight into spin, charge and lattice modulations at SrFeO 3-x/SrTiO 3 interfaces. NANOSCALE 2021; 13:6066-6075. [PMID: 33616142 DOI: 10.1039/d0nr07697j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Novel phenomena and functionalities at interfaces of oxide heterostructures are currently of great interest in a wide range of applications. At such interfaces, charge, spin, orbital and lattice ordering coexist and correlate closely, contributing to rich functional responses. By using atomically resolved imaging and spectroscopy techniques, we investigated magnetic behaviors and structural modulation at the SrFeO3-x/SrTiO3 interface. Fe/Ti element intermixing and oxygen vacancies occurred across a few unit cells at the interface. Furthermore, antiferromagnetic spin ordering of Fe with different valence states in the interface of SrFeO3-x/SrTiO3 induced uncompensated magnetic moments. Compared to the SrFeO3-x/La0.3Sr0.7Al0.65Ta0.35O3 heterojunction, the variations of charge and lattice order parameters at the SrFeO3-x/SrTiO3 interfaces were also determined by advanced electron microscopy, which provided a good understanding of the physical origin of disparate macroscopic magnetic properties, further investigated by magnetometer measurements and X-ray magnetic circular dichroism (XMCD) spectra. These studies provide comprehensive insight into the interfacial modulation of ferrite oxide, which may be useful for designing future devices in oxide electronics.
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Affiliation(s)
- Kun Xu
- National Center for Electron Microscopy in Beijing, Key Laboratory of Advanced Materials (MOE), The State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, People's Republic of China.
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14
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Löffler S, Stöger-Pollach M, Steiger-Thirsfeld A, Hetaba W, Schattschneider P. Exploiting the Acceleration Voltage Dependence of EMCD. MATERIALS (BASEL, SWITZERLAND) 2021; 14:1314. [PMID: 33803401 PMCID: PMC7967140 DOI: 10.3390/ma14051314] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Revised: 02/19/2021] [Accepted: 02/26/2021] [Indexed: 11/17/2022]
Abstract
Energy-loss magnetic chiral dichroism (EMCD) is a versatile method for measuring magnetism down to the atomic scale in transmission electron microscopy (TEM). As the magnetic signal is encoded in the phase of the electron wave, any process distorting this characteristic phase is detrimental for EMCD. For example, elastic scattering gives rise to a complex thickness dependence of the signal. Since the details of elastic scattering depend on the electron's energy, EMCD strongly depends on the acceleration voltage. Here, we quantitatively investigate this dependence in detail, using a combination of theory, numerical simulations, and experimental data. Our formulas enable scientists to optimize the acceleration voltage when performing EMCD experiments.
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Affiliation(s)
- Stefan Löffler
- University Service Centre for Transmission Electron Microscopy, TU Wien, Wiedner Hauptstraße 8-10/E057-02, 1040 Wien, Austria; (M.S.-P.); (A.S.-T.); (P.S.)
| | - Michael Stöger-Pollach
- University Service Centre for Transmission Electron Microscopy, TU Wien, Wiedner Hauptstraße 8-10/E057-02, 1040 Wien, Austria; (M.S.-P.); (A.S.-T.); (P.S.)
| | - Andreas Steiger-Thirsfeld
- University Service Centre for Transmission Electron Microscopy, TU Wien, Wiedner Hauptstraße 8-10/E057-02, 1040 Wien, Austria; (M.S.-P.); (A.S.-T.); (P.S.)
| | - Walid Hetaba
- Max Planck Institute for Chemical Energy Conversion, Stiftstraße 34-36, 45470 Mülheim an der Ruhr, Germany;
| | - Peter Schattschneider
- University Service Centre for Transmission Electron Microscopy, TU Wien, Wiedner Hauptstraße 8-10/E057-02, 1040 Wien, Austria; (M.S.-P.); (A.S.-T.); (P.S.)
- Institute of Solid State Physics, TU Wien, Wiedner Hauptstraße 8-10/E138-03, 1040 Wien, Austria
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15
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Ali H, Rusz J, Warnatz T, Hjörvarsson B, Leifer K. Simultaneous mapping of EMCD signals and crystal orientations in a transmission electron microscope. Sci Rep 2021; 11:2180. [PMID: 33500427 PMCID: PMC7838276 DOI: 10.1038/s41598-021-81071-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Accepted: 12/17/2020] [Indexed: 11/09/2022] Open
Abstract
When magnetic properties are analysed in a transmission electron microscope using the technique of electron magnetic circular dichroism (EMCD), one of the critical parameters is the sample orientation. Since small orientation changes can have a strong impact on the measurement of the EMCD signal and such measurements need two separate measurements of conjugate EELS spectra, it is experimentally non-trivial to measure the EMCD signal as a function of sample orientation. Here, we have developed a methodology to simultaneously map the quantitative EMCD signals and the local orientation of the crystal. We analyse, both experimentally and by simulations, how the measured magnetic signals evolve with a change in the crystal tilt. Based on this analysis, we establish an accurate relationship between the crystal orientations and the EMCD signals. Our results demonstrate that a small variation in crystal tilt can significantly alter the strength of the EMCD signal. From an optimisation of the crystal orientation, we obtain quantitative EMCD measurements.
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Affiliation(s)
- Hasan Ali
- Applied Materials Science, Department of Materials Science and Engineering, Uppsala University, Box 534, 75121, Uppsala, Sweden.,Department of Electrical Engineering, Mirpur University of Science and Technology (MUST), Mirpur, 10250, AJK, Pakistan.,Department of Materials and Environmental Chemistry, Stockholm University, 10691, Stockholm, Sweden
| | - Jan Rusz
- Department of Physics and Astronomy, Uppsala University, Box 516, 75120, Uppsala, Sweden
| | - Tobias Warnatz
- Department of Physics and Astronomy, Uppsala University, Box 516, 75120, Uppsala, Sweden
| | - Björgvin Hjörvarsson
- Department of Physics and Astronomy, Uppsala University, Box 516, 75120, Uppsala, Sweden
| | - Klaus Leifer
- Applied Materials Science, Department of Materials Science and Engineering, Uppsala University, Box 534, 75121, Uppsala, Sweden.
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16
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Affiliation(s)
- Dongdong Xiao
- Beijing National Laboratory for Condensed Matter PhysicsInstitute of PhysicsChinese Academy of Sciences Beijing 100190 China
| | - Lin Gu
- Beijing National Laboratory for Condensed Matter PhysicsInstitute of PhysicsChinese Academy of Sciences Beijing 100190 China
- School of physical sciencesUniversity of Chinese Academy of Sciences Beijing 100049 China
- Songshan Lake Materials Laboratory Dongguan Guangdong 523808 China
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17
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Wu X, Hao C, Xu L, Kuang H, Xu C. Chiromagnetic Plasmonic Nanoassemblies with Magnetic Field Modulated Chiral Activity. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2020; 16:e1905734. [PMID: 31851415 DOI: 10.1002/smll.201905734] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 11/13/2019] [Indexed: 06/10/2023]
Abstract
Chiral plasmonic nanoassemblies, which exhibit outstanding chiroptical activity in the visible or near-infrared region, are popular candidates in molecular sensing, polarized nanophotonics, and biomedical applications. Their optical chirality can be modulated by manipulating chemical molecule stimuli or replacing the building blocks. However, instead of irreversible chemical or material changes, real-time control of optical activity is desired for reversible and noninvasive physical regulating methods, which is a challenging research field. Here, the directionally and reversibly switching optical chirality of magneto-plasmonic nanoassemblies is demonstrated by the application of an external magnetic field. The gold-magnetic nanoparticles core-satellite (Au@Fe3 O4 ) nanostructures exhibit chiral activity in the UV-visible range, and the circular dichroism signal is 12 times greater under the magnetic field. Significantly, the chiral signal can be reversed by regulating the direction of the applied magnetic field. The attained magnetic field-regulated chirality is attributed to the large contributions of the magnetic dipole moments to polarization rotation. This magnetic field-modulated optical activity may be pivotal for photonic devices, information communication, as well as chiral metamaterials.
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Affiliation(s)
- Xiaoling Wu
- State Key Lab of Food Science and Technology, International Joint Research Laboratory for Biointerface and Biodetection, Collaborative Innovation Center of Food Safety and Quality Control in Jiangsu Province, School of Food Science and Technology, Jiangnan University, Wuxi, Jiangsu, 214122, P. R. China
| | - Changlong Hao
- State Key Lab of Food Science and Technology, International Joint Research Laboratory for Biointerface and Biodetection, Collaborative Innovation Center of Food Safety and Quality Control in Jiangsu Province, School of Food Science and Technology, Jiangnan University, Wuxi, Jiangsu, 214122, P. R. China
| | - Liguang Xu
- State Key Lab of Food Science and Technology, International Joint Research Laboratory for Biointerface and Biodetection, Collaborative Innovation Center of Food Safety and Quality Control in Jiangsu Province, School of Food Science and Technology, Jiangnan University, Wuxi, Jiangsu, 214122, P. R. China
| | - Hua Kuang
- State Key Lab of Food Science and Technology, International Joint Research Laboratory for Biointerface and Biodetection, Collaborative Innovation Center of Food Safety and Quality Control in Jiangsu Province, School of Food Science and Technology, Jiangnan University, Wuxi, Jiangsu, 214122, P. R. China
| | - Chuanlai Xu
- State Key Lab of Food Science and Technology, International Joint Research Laboratory for Biointerface and Biodetection, Collaborative Innovation Center of Food Safety and Quality Control in Jiangsu Province, School of Food Science and Technology, Jiangnan University, Wuxi, Jiangsu, 214122, P. R. China
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18
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Thersleff T, Schönström L, Tai CW, Adam R, Bürgler DE, Schneider CM, Muto S, Rusz J. Single-pass STEM-EMCD on a zone axis using a patterned aperture: progress in experimental and data treatment methods. Sci Rep 2019; 9:18170. [PMID: 31796786 PMCID: PMC6890689 DOI: 10.1038/s41598-019-53373-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Accepted: 10/22/2019] [Indexed: 11/08/2022] Open
Abstract
Measuring magnetic moments in ferromagnetic materials at atomic resolution is theoretically possible using the electron magnetic circular dichroism (EMCD) technique in a (scanning) transmission electron microscope ((S)TEM). However, experimental and data processing hurdles currently hamper the realization of this goal. Experimentally, the sample must be tilted to a zone-axis orientation, yielding a complex distribution of magnetic scattering intensity, and the same sample region must be scanned multiple times with sub-atomic spatial registration necessary at each pass. Furthermore, the weak nature of the EMCD signal requires advanced data processing techniques to reliably detect and quantify the result. In this manuscript, we detail our experimental and data processing progress towards achieving single-pass zone-axis EMCD using a patterned aperture. First, we provide a comprehensive data acquisition and analysis strategy for this and other EMCD experiments that should scale down to atomic resolution experiments. Second, we demonstrate that, at low spatial resolution, promising EMCD candidate signals can be extracted, and that these are sensitive to both crystallographic orientation and momentum transfer.
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Affiliation(s)
- Thomas Thersleff
- Stockholm University, Department of Materials and Environmental Chemistry, 10691, Stockholm, Sweden.
| | - Linus Schönström
- Stockholm University, Department of Materials and Environmental Chemistry, 10691, Stockholm, Sweden
- Uppsala University, Department of Physics and Astronomy, Box 516, 75120, Uppsala, Sweden
| | - Cheuk-Wai Tai
- Stockholm University, Department of Materials and Environmental Chemistry, 10691, Stockholm, Sweden
| | - Roman Adam
- Forschungszentrum Jülich GmbH, Peter Grünberg Institut, D-52425, Jülich, Germany
| | - Daniel E Bürgler
- Forschungszentrum Jülich GmbH, Peter Grünberg Institut, D-52425, Jülich, Germany
| | - Claus M Schneider
- Forschungszentrum Jülich GmbH, Peter Grünberg Institut, D-52425, Jülich, Germany
| | - Shunsuke Muto
- Nagoya University, Institute of Materials and Systems for Sustainability, Nagoya, 464-8603, Japan
| | - Ján Rusz
- Uppsala University, Department of Physics and Astronomy, Box 516, 75120, Uppsala, Sweden
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Zhong X, Lin J, Kao S, Liao Z, Zhu J, Huang X, Zhang R, Xin HL. Atomistic Defect Makes a Phase Plate for the Generation and High-Angular Splitting of Electron Vortex Beams. ACS NANO 2019; 13:3964-3970. [PMID: 30794384 DOI: 10.1021/acsnano.8b07437] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Topological defects in solid-state materials by breaking the translational symmetry offer emerging properties that are not present in their parental phases. For example, edge dislocations-the 2π phase-winding topological defects-in antiferromagnetic NiO crystals can exhibit ferromagnetic behaviors. Herein, we study how these defects could give rise to topological orders when they interact with a high-energy electron beam. To probe this interaction, we formed a coherent electron nanobeam in a scanning transmission electron microscope and recorded the far-field transmitted patterns as the beam steps through the edge dislocation core in [001] NiO. Surprisingly, we found the amplitude patterns of the ⟨020⟩ Bragg disks evolve in a similar manner to the evolution of an annular solar eclipse. Using the ptychographic technique, we recovered the missing phase information in the diffraction plane and revealed the topological phase vortices in the diffracted beams. Through atomic topological defects, the wave function of electrons can be converted from plane wave to electron vortex. Technologically, this approach provides a feasible route for the fabrication of phase plates that can generate electron vortex beams with an angular separation that is 3 orders of magnitude larger than what traditional nanofabrication technology can offer. This advance will enable the collection of magnetic circular dichroism spectra with high spatial resolution and high efficiency, boosting the understanding of the relationship between symmetry breaking and magnetic property of individual topological defect at the atomic scale.
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Affiliation(s)
- Xiaoyan Zhong
- National Center for Electron Microscopy in Beijing, Key Laboratory of Advanced Materials (MOE), State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering , Tsinghua University , Beijing 100084 , China
| | - Jie Lin
- National Center for Electron Microscopy in Beijing, Key Laboratory of Advanced Materials (MOE), State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering , Tsinghua University , Beijing 100084 , China
| | - ShowShiuan Kao
- National Center for Electron Microscopy in Beijing, Key Laboratory of Advanced Materials (MOE), State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering , Tsinghua University , Beijing 100084 , China
| | - Zhenyu Liao
- National Center for Electron Microscopy in Beijing, Key Laboratory of Advanced Materials (MOE), State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering , Tsinghua University , Beijing 100084 , China
| | - Jing Zhu
- National Center for Electron Microscopy in Beijing, Key Laboratory of Advanced Materials (MOE), State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering , Tsinghua University , Beijing 100084 , China
| | - Xiaojing Huang
- National Synchrotron Light Source II , Brookhaven National Laboratory , Upton , New York 11973 , United States
| | - Rui Zhang
- Department of Physics and Astronomy , University of California , Irvine , California 92697 , United States
| | - Huolin L Xin
- Department of Physics and Astronomy , University of California , Irvine , California 92697 , United States
- Center for Functional Nanomaterials , Brookhaven National Laboratory , Upton , New York 11973 , United States
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20
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Song D, Wang Z, Zhu J. Magnetic measurement by electron magnetic circular dichroism in the transmission electron microscope. Ultramicroscopy 2019; 201:1-17. [PMID: 30904784 DOI: 10.1016/j.ultramic.2019.03.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Revised: 03/05/2019] [Accepted: 03/18/2019] [Indexed: 10/27/2022]
Abstract
Magnetic measurement by transmitted electrons at nanometer or even atomic scale is always an attractive and challenging issue in the transmission electron microscope. Electron magnetic circular dichroism, proposed in 2003 and realized in 2006, opens a new insight into the measurement of local magnetic properties. Later, it is developed into a powerful technique for quantitative magnetic measurement with site specificity and element specificity at high spatial resolution over years of efforts, both in the aspect of theory and experiments. The novel technique has been widely applied to the characterization of magnetic materials now. This present review gives an overview of its development and applications in the past fifteen years since its invention. The theory of electron magnetic circular dichroism and its development are reviewed. The diffraction geometry and experimental setups are summarized. The general way for quantitative measurement of magnetic parameters is presented with typical cases. Representative breakthroughs in method development and applications over a wide range of materials are then described. Finally, prospects for future development are briefly discussed.
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Affiliation(s)
- Dongsheng Song
- National Center for Electron Microscopy in Beijing, Key Laboratory of Advanced Materials (MOE), The State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China.
| | - Ziqiang Wang
- National Center for Electron Microscopy in Beijing, Key Laboratory of Advanced Materials (MOE), The State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China
| | - Jing Zhu
- National Center for Electron Microscopy in Beijing, Key Laboratory of Advanced Materials (MOE), The State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China.
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21
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Chen X, Higashikozono S, Ito K, Jin L, Ho PL, Yu CP, Tai NH, Mayer J, Dunin-Borkowski RE, Suemasu T, Zhong X. Nanoscale measurement of giant saturation magnetization in α″-Fe 16N 2 by electron energy-loss magnetic chiral dichroism. Ultramicroscopy 2019; 203:37-43. [PMID: 30862364 DOI: 10.1016/j.ultramic.2019.02.016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2018] [Revised: 02/10/2019] [Accepted: 02/18/2019] [Indexed: 10/27/2022]
Abstract
Metastable α″-Fe16N2 thin films were reported to have a giant saturation magnetization of above 2200 emu/cm3 in 1972 and have been considered as candidates for next-generation rare-earth-free permanent magnetic materials. However, their magnetic properties have not been confirmed unequivocally. As a result of the limited spatial resolution of most magnetic characterization techniques, it is challenging to measure the saturation magnetization of the α″-Fe16N2 phase, as it is often mixed with the parent α'-Fe8N phase in thin films. Here, we use electron energy-loss magnetic chiral dichroism (EMCD), aberration-corrected transmission electron microscopy, X-ray diffraction and macroscopic magnetic measurements to study α″-Fe16N2 (containing ordered N atoms) and α'-Fe8N (containing disordered N atoms). The ratio of saturation magnetization in α″-Fe16N2 to that in α'-Fe8N is determined to be 1.31 ± 0.10 from quantitative EMCD measurements and dynamical diffraction calculations, confirming the giant saturation magnetization of α″-Fe16N2. Crystallographic information is also obtained about the two phases, which are mixed on the nanoscale.
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Affiliation(s)
- Xinfeng Chen
- National Center for Electron Microscopy in Beijing, Key Laboratory of Advanced Materials (MOE), The State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China
| | - Soma Higashikozono
- Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8573, Japan
| | - Keita Ito
- Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8573, Japan
| | - Lei Jin
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, Forschungszentrum Jülich GmbH, Jülich 52425, Germany
| | - Ping-Luen Ho
- National Center for Electron Microscopy in Beijing, Key Laboratory of Advanced Materials (MOE), The State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China
| | - Chu-Ping Yu
- National Center for Electron Microscopy in Beijing, Key Laboratory of Advanced Materials (MOE), The State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China; Department of Materials Science and Engineering, National Tsing-Hua University, Hsinchu 30013, Taiwan
| | - Nyan-Hwa Tai
- Department of Materials Science and Engineering, National Tsing-Hua University, Hsinchu 30013, Taiwan
| | - Joachim Mayer
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, Forschungszentrum Jülich GmbH, Jülich 52425, Germany; Central Facility for Electron Microscopy, RWTH Aachen University, Aachen 52074, Germany
| | - Rafal E Dunin-Borkowski
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, Forschungszentrum Jülich GmbH, Jülich 52425, Germany
| | - Takashi Suemasu
- Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8573, Japan
| | - Xiaoyan Zhong
- National Center for Electron Microscopy in Beijing, Key Laboratory of Advanced Materials (MOE), The State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China.
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22
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Negi D, Spiegelberg J, Muto S, Thersleff T, Ohtsuka M, Schönström L, Tatsumi K, Rusz J. Proposal for Measuring Magnetism with Patterned Apertures in a Transmission Electron Microscope. PHYSICAL REVIEW LETTERS 2019; 122:037201. [PMID: 30735420 DOI: 10.1103/physrevlett.122.037201] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2018] [Revised: 10/13/2018] [Indexed: 06/09/2023]
Abstract
We propose a magnetic measurement method utilizing a patterned postsample aperture in a transmission electron microscope. While utilizing electron magnetic circular dichroism, the method circumvents previous needs to shape the electron probe to an electron vortex beam or astigmatic beam. The method can be implemented in standard scanning transmission electron microscopes by replacing the spectrometer entrance aperture with a specially shaped aperture, hereafter called a ventilator aperture. The proposed setup is expected to work across the whole range of beam sizes-from wide parallel beams down to atomic resolution magnetic spectrum imaging.
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Affiliation(s)
- Devendra Negi
- Department of Physics and Astronomy, Uppsala University, P.O. Box 516, 75120 Uppsala, Sweden
| | - Jakob Spiegelberg
- Department of Physics and Astronomy, Uppsala University, P.O. Box 516, 75120 Uppsala, Sweden
| | - Shunsuke Muto
- Electron Nanoscopy Section, Advanced Measurement Technology Center, Institute of Materials and Systems for Sustainability, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan
| | - Thomas Thersleff
- Department of Materials and Environmental Chemistry, Stockholm University, Svante Arrhenius väg 16C, 106 91 Stockholm, Sweden
| | - Masahiro Ohtsuka
- Department of Materials Physics, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan
| | - Linus Schönström
- Department of Materials and Environmental Chemistry, Stockholm University, Svante Arrhenius väg 16C, 106 91 Stockholm, Sweden
| | - Kazuyoshi Tatsumi
- Advanced Measurement Technology Center, Institute of Materials and Systems for Sustainability, Nagoya University, Chikusa, Nagoya 464-8603, Japan
| | - Ján Rusz
- Department of Physics and Astronomy, Uppsala University, P.O. Box 516, 75120 Uppsala, Sweden
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Ali H, Warnatz T, Xie L, Hjörvarsson B, Leifer K. Quantitative EMCD by use of a double aperture for simultaneous acquisition of EELS. Ultramicroscopy 2019; 196:192-196. [DOI: 10.1016/j.ultramic.2018.10.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Revised: 10/21/2018] [Accepted: 10/25/2018] [Indexed: 10/28/2022]
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Effect of cation ratio and order on magnetic circular dichroism in the double perovskite Sr 2Fe 1+xRe 1-xO 6. Ultramicroscopy 2018; 193:137-142. [PMID: 30005323 DOI: 10.1016/j.ultramic.2018.06.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2018] [Revised: 05/10/2018] [Accepted: 06/10/2018] [Indexed: 11/22/2022]
Abstract
Superexchange-based magnetic coupling of the two B-site cations in rock-salt-ordered double perovskite oxides is extremely sensitive to the cation ratio and degree of order. However, as a result of the limited spatial resolution of most magnetic characterization techniques, it is challenging to establish a direct relationship between magnetic properties and structure in these materials, including the effects of elemental segregation and cation disorder. Here, we use electron energy-loss magnetic chiral dichroism together with aberration-corrected electron microscopy and spectroscopy to record magnetic circular dichroism (MCD) spectra at the nm scale, in combination with structural and chemical information at the atomic scale from the very same region. We study nanoscale phases in ordered Sr2[Fe][Re]O6, ordered Sr2[Fe][Fe1/5Re4/5]O6 and disordered Sr[Fe4/5Re1/5]O3 individually, in order to understand the role of cation ratio and order on local magnetic coupling. When compared with ordered Sr2[Fe][Re]O6, we find that antiferromagnetic Fe3+-O2--Fe3+superexchange interactions arising from an excess of Fe suppress the MCD signal from Fe cations in ordered Sr2[Fe][Fe1/5Re4/5]O6, while dominant Fe3+-O2--Fe3+antiferromagnetic coupling in disordered Sr[Fe4/5Re1/5]O3 leads to a decrease in MCD signal down to the noise level. Our work demonstrates a protocol that can be used to correlate crystallographic, electronic and magnetic information in materials such as Sr2Fe1+xRe1-xO6, in order to provide insight into structure-property relationships in double perovskite oxides at the atomic scale.
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