1
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Kane M, Bhandari C, Holtz ME, Balakrishnan PP, Grutter AJ, Fitzsimmons M, Yang CY, Satpathy S, Paudyal D, Suzuki Y. Emergent Ferromagnetism in CaRuO 3/CaMnO 3 (111)-Oriented Superlattices. Nano Lett 2024; 24:2567-2573. [PMID: 38367281 DOI: 10.1021/acs.nanolett.3c04623] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/19/2024]
Abstract
The boundary between CaRuO3 and CaMnO3 is an ideal test bed for emergent magnetic ground states stabilized through interfacial electron interactions. In this system, nominally antiferromagnetic and paramagnetic materials combine to yield interfacial ferromagnetism in CaMnO3 due to electron leakage across the interface. In this work, we show that the crystal symmetry at the surface is a critical factor determining the nature of the interfacial interactions. Specifically, by growing CaRuO3/CaMnO3 heterostructures along the (111) instead of the (001) crystallographic axis, we achieve a 3-fold enhancement of the magnetization and involve the CaRuO3 layers in the ferromagnetism, which now spans both constituent materials. The stabilization of a net magnetic moment in CaRuO3 through strain effects has been long-sought but never consistently achieved, and our observations demonstrate the importance of interface engineering in the development of new functional heterostructures.
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Affiliation(s)
- Margaret Kane
- Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
- Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, United States
| | - Churna Bhandari
- Ames National Laboratory, Iowa State University, Ames, Iowa 50011, United States
| | - Megan E Holtz
- Metallurgical and Materials Engineering, Colorado School of Mines, Golden, Colorado 80401, United States
| | - Purnima P Balakrishnan
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Alexander J Grutter
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Michael Fitzsimmons
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830 United States
| | - Chao-Yao Yang
- Department of Material Science and Engineering, National Yang Ming Chiao Tung University, Hsinchu City 30100, Taiwan
| | - Sashi Satpathy
- Department of Physics & Astronomy, University of Missouri, Columbia, Missouri 65211, United States
| | - Durga Paudyal
- Ames National Laboratory, Iowa State University, Ames, Iowa 50011, United States
- Department of Electrical and Computer Engineering, Iowa State University, Ames, Iowa 50011, United States
| | - Yuri Suzuki
- Department of Applied Physics, Stanford University, Stanford, California 94305, United States
- Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, United States
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2
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Holtz ME, Padgett E, Johnston-Peck AC, Levin I, Muller DA, Herzing AA. Mapping Polar Distortions using Nanobeam Electron Diffraction and a Cepstral Approach. Microsc Microanal 2023; 29:1422-1435. [PMID: 37488825 DOI: 10.1093/micmic/ozad070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Revised: 05/26/2023] [Accepted: 06/18/2023] [Indexed: 07/26/2023]
Abstract
Measuring local polar ordering is key to understanding ferroelectricity in thin films, especially for systems with small domains or significant disorder. Scanning nanobeam electron diffraction (NBED) provides an effective local probe of lattice parameters, local fields, polarization directions, and charge densities, which can be analyzed using a relatively low beam dose over large fields of view. However, quantitatively extracting the magnitudes and directions of polarization vectors from NBED remains challenging. Here, we use a cepstral approach, similar to a pair distribution function, to determine local polar displacements that drive ferroelectricity from NBED patterns. Because polar distortions generate asymmetry in the diffraction pattern intensity, we can efficiently recover the underlying displacements from the imaginary part of the cepstrum transform. We investigate the limits of this technique using analytical and simulated data and give experimental examples, achieving the order of 1.1 pm precision and mapping of polar displacements with nanometer resolution.
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Affiliation(s)
- Megan E Holtz
- Material Measurement Laboratory, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD 20899, USA
- School of Applied and Engineering Physics, Cornell University, 142 Sciences Drive, Ithaca, NY 14853, USA
- Department of Metallurgical and Materials Engineering, Colorado School of Mines, 1301 19th Street, Golden, CO 80401, USA
| | - Elliot Padgett
- School of Applied and Engineering Physics, Cornell University, 142 Sciences Drive, Ithaca, NY 14853, USA
| | - Aaron C Johnston-Peck
- Material Measurement Laboratory, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD 20899, USA
| | - Igor Levin
- Material Measurement Laboratory, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD 20899, USA
| | - David A Muller
- School of Applied and Engineering Physics, Cornell University, 142 Sciences Drive, Ithaca, NY 14853, USA
| | - Andrew A Herzing
- Material Measurement Laboratory, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD 20899, USA
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3
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Holtz ME, Herzing A, Gorman B. Scanning Nanobeam Electron Diffraction for Atomic Scale Tomography. Microsc Microanal 2023; 29:600-601. [PMID: 37613400 DOI: 10.1093/micmic/ozad067.290] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/25/2023]
Affiliation(s)
- Megan E Holtz
- Department of Metallurgy and Materials Engineering, Colorado School of Mines, Golden, CO, United States
| | - Andrew Herzing
- Materials Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD, United States
| | - Brian Gorman
- Department of Metallurgy and Materials Engineering, Colorado School of Mines, Golden, CO, United States
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4
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Zhang P, Balakrishnan PP, Eckberg C, Deng P, Nozaki T, Chong SK, Quarterman P, Holtz ME, Maranville BB, Qiu G, Pan L, Emmanouilidou E, Ni N, Sahashi M, Grutter A, Wang KL. Exchange-Biased Quantum Anomalous Hall Effect. Adv Mater 2023:e2300391. [PMID: 37207689 DOI: 10.1002/adma.202300391] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Revised: 02/28/2023] [Indexed: 05/21/2023]
Abstract
The quantum anomalous Hall (QAH) effect is characterized by a dissipationless chiral edge state with a quantized Hall resistance at zero magnetic field. Manipulating the QAH state is of great importance in both the understanding of topological quantum physics and the implementation of dissipationless electronics. Here, we realized the QAH effect in the magnetic topological insulator Cr-doped (Bi,Sb)2 Te3 (CBST) grown on an uncompensated antiferromagnetic insulator Al-doped Cr2 O3 . Through polarized neutron reflectometry (PNR), we find a strong exchange coupling between CBST and Al-Cr2 O3 surface spins fixing interfacial magnetic moments perpendicular to the film plane. The interfacial coupling results in an exchange-biased QAH effect. We further demonstrate that the magnitude and sign of the exchange bias can be effectively controlled using a field training process to set the magnetization of the Al-Cr2 O3 layer. Our work demonstrates the use of the exchange bias effect to effectively manipulate the QAH state, opening new possibilities in QAH-based spintronics. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Peng Zhang
- Department of Electrical and Computer Engineering, University of California Los Angeles, Los Angeles, CA, 90095, USA
| | - Purnima P Balakrishnan
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD, 20899-6102, USA
| | - Christopher Eckberg
- Department of Electrical and Computer Engineering, University of California Los Angeles, Los Angeles, CA, 90095, USA
- Fibertek Inc., Herndon, VA, 20171, USA
- US Army Research Laboratory, Adelphi, MD, 20783, USA
- US Army Research Laboratory, Playa Vista, CA, 90094, USA
| | - Peng Deng
- Department of Electrical and Computer Engineering, University of California Los Angeles, Los Angeles, CA, 90095, USA
| | - Tomohiro Nozaki
- Department of Electronic Engineering, Tohoku University, Sendai, 980-8579, Japan
| | - Su Kong Chong
- Department of Electrical and Computer Engineering, University of California Los Angeles, Los Angeles, CA, 90095, USA
| | - Patrick Quarterman
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD, 20899-6102, USA
| | - Megan E Holtz
- Material Measurement Laboratory, National Institute of Standards and Technology (NIST), Gaithersburg, Maryland, 20899, USA
| | - Brian B Maranville
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD, 20899-6102, USA
| | - Gang Qiu
- Department of Electrical and Computer Engineering, University of California Los Angeles, Los Angeles, CA, 90095, USA
| | - Lei Pan
- Department of Electrical and Computer Engineering, University of California Los Angeles, Los Angeles, CA, 90095, USA
| | - Eve Emmanouilidou
- Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, CA, 90095, USA
| | - Ni Ni
- Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, CA, 90095, USA
| | - Masashi Sahashi
- Department of Electronic Engineering, Tohoku University, Sendai, 980-8579, Japan
| | - Alexander Grutter
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD, 20899-6102, USA
| | - Kang L Wang
- Department of Electrical and Computer Engineering, University of California Los Angeles, Los Angeles, CA, 90095, USA
- Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, CA, 90095, USA
- Department of Materials Science and Engineering, University of California, Los Angeles, CA, 90095, USA
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5
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Deng P, Grutter A, Han Y, Holtz ME, Zhang P, Quarterman P, Pan S, Qi S, Qiao Z, Wang KL. Correction to Topological Surface State Annihilation and Creation in SnTe/Cr x(BiSb) 2-xTe 3 Heterostructures. Nano Lett 2022; 22:8394. [PMID: 36227014 DOI: 10.1021/acs.nanolett.2c03339] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Affiliation(s)
- Peng Deng
- Department of Electrical and Computer Engineering, University of California, Los Angeles, California 90095, United States
- Beijing Academy of Quantum Information Sciences, Beijing 100193, China
| | - Alexander Grutter
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-6102, United States
| | - Yulei Han
- ICQD, Hefei National Laboratory for Physical Sciences at Microscale, CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Anhui 230026, China
| | - Megan E Holtz
- Materials Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-6102, United States
| | - Peng Zhang
- Department of Electrical and Computer Engineering, University of California, Los Angeles, California 90095, United States
| | - Patrick Quarterman
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-6102, United States
| | - Shuaihang Pan
- Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, California 90095, United States
| | - Shifei Qi
- ICQD, Hefei National Laboratory for Physical Sciences at Microscale, CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Anhui 230026, China
- College of Physics and Hebei Advanced Thin Film Laboratory, Hebei Normal University, Hebei 050024, China
| | - Zhenhua Qiao
- ICQD, Hefei National Laboratory for Physical Sciences at Microscale, CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Anhui 230026, China
| | - Kang L Wang
- Department of Electrical and Computer Engineering, University of California, Los Angeles, California 90095, United States
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, United States
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6
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Sherbondy R, Smaha RW, Bartel CJ, Holtz ME, Talley KR, Levy-Wendt B, Perkins CL, Eley S, Zakutayev A, Brennecka GL. High-Throughput Selection and Experimental Realization of Two New Ce-Based Nitride Perovskites: CeMoN 3 and CeWN 3. Chem Mater 2022; 34:6883-6893. [PMID: 35965892 PMCID: PMC9367680 DOI: 10.1021/acs.chemmater.2c01282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Revised: 07/22/2022] [Indexed: 06/15/2023]
Abstract
Nitride perovskites have only been experimentally realized in very few cases despite the widespread existence and commercial importance of perovskite materials. From oxide perovskites used in ultrasonics to halide perovskites that have revolutionized the photovoltaics industry, the discovery of new perovskite materials has historically impacted a wide number of fields. Here, we add two new perovskites, CeWN3 and CeMoN3, to the list of experimentally realized perovskite nitrides using high-throughput computational screening and subsequent high-throughput thin film growth techniques. Candidate compositions are first down-selected using a tolerance factor and then thermochemical stability. A novel competing fluorite-family phase is identified for both material systems, which we hypothesize is a transient intermediate phase that crystallizes during the evolution from an amorphous material to a stable perovskite. Different processing routes to overcome the competing fluorite phase and obtain phase-pure nitride perovskites are demonstrated for the CeMoN3-x and CeWN3-x material systems, which provide a starting point for the development of future nitride perovskites. Additionally, we find that these new perovskite phases have interesting low-temperature magnetic behavior: CeMoN3-x orders antiferromagnetically below T N ≈ 8 K with indications of strong magnetic frustration, while CeWN3-x exhibits no long-range order down to T = 2 K but has strong antiferromagnetic correlations. This work demonstrates the importance and effectiveness of using high-throughput techniques, both computational and experimental: they are integral to optimize the process of realizing two entirely novel nitride perovskites.
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Affiliation(s)
- Rachel Sherbondy
- Materials
Science Center, National Renewable Energy
Laboratory, Golden, Colorado 80401, United States
- Metallurgical
and Materials Engineering Department, Colorado
School of Mines, Golden, Colorado 80401, United States
| | - Rebecca W. Smaha
- Materials
Science Center, National Renewable Energy
Laboratory, Golden, Colorado 80401, United States
| | - Christopher J. Bartel
- Department
of Materials Science and Engineering, University
of California, Berkeley, Berkeley, California 94720, United States
| | - Megan E. Holtz
- Metallurgical
and Materials Engineering Department, Colorado
School of Mines, Golden, Colorado 80401, United States
| | - Kevin R. Talley
- Materials
Science Center, National Renewable Energy
Laboratory, Golden, Colorado 80401, United States
| | - Ben Levy-Wendt
- SLAC
National Accelerator Laboratory, Menlo Park, California 94025, United States
- Department
of Mechanical Engineering, Stanford University, Palo Alto, California 94305, United States
| | - Craig L. Perkins
- Materials
Science Center, National Renewable Energy
Laboratory, Golden, Colorado 80401, United States
| | - Serena Eley
- Department
of Physics, Colorado School of Mines, Golden, Colorado 80401, United States
| | - Andriy Zakutayev
- Materials
Science Center, National Renewable Energy
Laboratory, Golden, Colorado 80401, United States
| | - Geoff L. Brennecka
- Metallurgical
and Materials Engineering Department, Colorado
School of Mines, Golden, Colorado 80401, United States
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7
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Deng P, Grutter A, Han Y, Holtz ME, Zhang P, Quarterman P, Pan S, Qi S, Qiao Z, Wang KL. Topological Surface State Annihilation and Creation in SnTe/Cr x(BiSb) 2-xTe 3 Heterostructures. Nano Lett 2022; 22:5735-5741. [PMID: 35850534 DOI: 10.1021/acs.nanolett.2c00774] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Topological surface states are a new class of electronic states with novel properties, including the potential for annihilation between surface states from two topological insulators at a common interface. Here, we report the annihilation and creation of topological surface states in the SnTe/Crx(BiSb)2-xTe3 (CBST) heterostructures as evidenced by magneto-transport, polarized neutron reflectometry, and first-principles calculations. Our results show that topological surface states are induced in the otherwise topologically trivial two-quintuple-layers thick CBST when interfaced with SnTe, as a result of the surface state annihilation at the SnTe/CBST interface. Moreover, we unveiled systematic changes in the transport behaviors of the heterostructures with respect to changing Fermi level and thickness. Our observation of surface state creation and annihilation demonstrates a promising way of designing and engineering topological surface states for dissipationless electronics.
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Affiliation(s)
- Peng Deng
- Department of Electrical and Computer Engineering, University of California, Los Angeles, California 90095, United States
- Beijing Academy of Quantum Information Science, Beijing 100193, China
| | - Alexander Grutter
- NIST Center for Neutron Research, National Institute of Standards and Technology, Maryland 20899-6102, United States
| | - Yulei Han
- ICQD, Hefei National Laboratory for Physical Sciences at Microscale, CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Anhui 230026, China
| | - Megan E Holtz
- Materials Measurement Laboratory, National Institute of Standards and Technology, Maryland 20899-6102, United States
| | - Peng Zhang
- Department of Electrical and Computer Engineering, University of California, Los Angeles, California 90095, United States
| | - Patrick Quarterman
- NIST Center for Neutron Research, National Institute of Standards and Technology, Maryland 20899-6102, United States
| | - Shuaihang Pan
- Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, California 90095, United States
| | - Shifei Qi
- ICQD, Hefei National Laboratory for Physical Sciences at Microscale, CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Anhui 230026, China
- College of Physics and Hebei Advanced Thin Film Laboratory, Hebei Normal University, Hebei 050024, China
| | - Zhenhua Qiao
- NIST Center for Neutron Research, National Institute of Standards and Technology, Maryland 20899-6102, United States
| | - Kang L Wang
- Department of Electrical and Computer Engineering, University of California, Los Angeles, California 90095, United States
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, United States
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8
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Huang W, Johnston-Peck AC, Wolter T, Yang WCD, Xu L, Oh J, Reeves BA, Zhou C, Holtz ME, Herzing AA, Lindenberg AM, Mavrikakis M, Cargnello M. Steam-created grain boundaries for methane C-H activation in palladium catalysts. Science 2021; 373:1518-1523. [PMID: 34554810 DOI: 10.1126/science.abj5291] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
[Figure: see text].
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Affiliation(s)
- Weixin Huang
- Department of Chemical Engineering, Stanford University, Stanford, CA 94305, USA
| | - Aaron C Johnston-Peck
- Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
| | - Trenton Wolter
- Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Wei-Chang D Yang
- Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
| | - Lang Xu
- Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Jinwon Oh
- Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305, USA
| | - Benjamin A Reeves
- Department of Chemical Engineering, Stanford University, Stanford, CA 94305, USA
| | - Chengshuang Zhou
- Department of Chemical Engineering, Stanford University, Stanford, CA 94305, USA
| | - Megan E Holtz
- Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
| | - Andrew A Herzing
- Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
| | - Aaron M Lindenberg
- Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305, USA.,Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
| | - Manos Mavrikakis
- Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Matteo Cargnello
- Department of Chemical Engineering, Stanford University, Stanford, CA 94305, USA.,SUNCAT Center for Interface Science and Catalysis, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
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9
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Fan Y, Finley J, Han J, Holtz ME, Quarterman P, Zhang P, Safi TS, Hou JT, Grutter AJ, Liu L. Resonant Spin Transmission Mediated by Magnons in a Magnetic Insulator Multilayer Structure. Adv Mater 2021; 33:e2008555. [PMID: 33899284 DOI: 10.1002/adma.202008555] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Revised: 02/15/2021] [Indexed: 06/12/2023]
Abstract
While being electrically insulating, magnetic insulators can behave as good spin conductors by carrying spin current with excited spin waves. So far, magnetic insulators are utilized in multilayer heterostructures for optimizing spin transport or to form magnon spin valves for reaching controls over the spin flow. In these studies, it remains an intensively visited topic as to what the corresponding roles of coherent and incoherent magnons are in the spin transmission. Meanwhile, understanding the underlying mechanism associated with spin transmission in insulators can help to identify new mechanisms that can further improve the spin transport efficiency. Here, by studying spin transport in a magnetic-metal/magnetic-insulator/platinum multilayer, it is demonstrated that coherent magnons can transfer spins efficiently above the magnon bandgap of magnetic insulators. Particularly the standing spin-wave mode can greatly enhance the spin flow by inducing a resonant magnon transmission. Furthermore, within the magnon bandgap, a shutdown of spin transmission due to the blocking of coherent magnons is observed. The demonstrated magnon transmission enhancement and filtering effect provides an efficient method for modulating spin current in magnonic devices.
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Affiliation(s)
- Yabin Fan
- Microsystems Technology Laboratories, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Joseph Finley
- Microsystems Technology Laboratories, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Jiahao Han
- Microsystems Technology Laboratories, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Megan E Holtz
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA
| | - Patrick Quarterman
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA
| | - Pengxiang Zhang
- Microsystems Technology Laboratories, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Taqiyyah S Safi
- Microsystems Technology Laboratories, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Justin T Hou
- Microsystems Technology Laboratories, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Alexander J Grutter
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA
| | - Luqiao Liu
- Microsystems Technology Laboratories, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
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10
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Chen Z, Jiang Y, Shao YT, Holtz ME, Odstrčil M, Guizar-Sicairos M, Hanke I, Ganschow S, Schlom DG, Muller DA. Electron ptychography achieves atomic-resolution limits set by lattice vibrations. Science 2021; 372:826-831. [DOI: 10.1126/science.abg2533] [Citation(s) in RCA: 45] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Accepted: 04/13/2021] [Indexed: 01/30/2023]
Affiliation(s)
- Zhen Chen
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, USA
| | - Yi Jiang
- Advanced Photon Source, Argonne National Laboratory, Lemont, IL 60439, USA
| | - Yu-Tsun Shao
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, USA
| | - Megan E. Holtz
- Department of Materials Science and Engineering, Cornell University, Ithaca, NY, USA
| | | | | | - Isabelle Hanke
- Leibniz-Institut für Kristallzüchtung, Max-Born-Str. 2, 12489 Berlin, Germany
| | - Steffen Ganschow
- Leibniz-Institut für Kristallzüchtung, Max-Born-Str. 2, 12489 Berlin, Germany
| | - Darrell G. Schlom
- Department of Materials Science and Engineering, Cornell University, Ithaca, NY, USA
- Leibniz-Institut für Kristallzüchtung, Max-Born-Str. 2, 12489 Berlin, Germany
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, NY, USA
| | - David A. Muller
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, USA
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, NY, USA
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11
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Holtz ME, Padgett ES, Steinhardt R, Brooks CM, Meier D, Schlom DG, Muller DA, Mundy JA. Dimensionality-Induced Change in Topological Order in Multiferroic Oxide Superlattices. Phys Rev Lett 2021; 126:157601. [PMID: 33929216 DOI: 10.1103/physrevlett.126.157601] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Revised: 10/12/2020] [Accepted: 02/18/2021] [Indexed: 06/12/2023]
Abstract
We construct ferroelectric (LuFeO_{3})_{m}/(LuFe_{2}O_{4}) superlattices with varying index m to study the effect of confinement on topological defects. We observe a thickness-dependent transition from neutral to charged domain walls and the emergence of fractional vortices. In thin LuFeO_{3} layers, the volume fraction of domain walls grows, lowering the symmetry from P6_{3}cm to P3c1 before reaching the nonpolar P6_{3}/mmc state, analogous to the group-subgroup sequence observed at the high-temperature ferroelectric to paraelectric transition. Our study shows how dimensional confinement stabilizes textures beyond those in bulk ferroelectric systems.
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Affiliation(s)
- Megan E Holtz
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA
| | - Elliot S Padgett
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA
| | - Rachel Steinhardt
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA
| | - Charles M Brooks
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA
| | - Dennis Meier
- Department of Materials Science and Engineering, Norwegian University of Science and Technology, NTNU, 7491 Trondheim, Norway
| | - Darrell G Schlom
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853, USA
- Leibniz-Institut für Kristallzüchtung, Max-Born-Straβe 2, 12489 Berlin, Germany
| | - David A Muller
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853, USA
| | - Julia A Mundy
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
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12
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Fan S, Das H, Rébola A, Smith KA, Mundy J, Brooks C, Holtz ME, Muller DA, Fennie CJ, Ramesh R, Schlom DG, McGill S, Musfeldt JL. Site-specific spectroscopic measurement of spin and charge in (LuFeO 3) m/(LuFe 2O 4) 1 multiferroic superlattices. Nat Commun 2020; 11:5582. [PMID: 33149138 PMCID: PMC7642375 DOI: 10.1038/s41467-020-19285-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2020] [Accepted: 10/07/2020] [Indexed: 11/09/2022] Open
Abstract
Interface materials offer a means to achieve electrical control of ferrimagnetism at room temperature as was recently demonstrated in (LuFeO3)m/(LuFe2O4)1 superlattices. A challenge to understanding the inner workings of these complex magnetoelectric multiferroics is the multitude of distinct Fe centres and their associated environments. This is because macroscopic techniques characterize average responses rather than the role of individual iron centres. Here, we combine optical absorption, magnetic circular dichroism and first-principles calculations to uncover the origin of high-temperature magnetism in these superlattices and the charge-ordering pattern in the m = 3 member. In a significant conceptual advance, interface spectra establish how Lu-layer distortion selectively enhances the Fe2+ → Fe3+ charge-transfer contribution in the spin-up channel, strengthens the exchange interactions and increases the Curie temperature. Comparison of predicted and measured spectra also identifies a non-polar charge ordering arrangement in the LuFe2O4 layer. This site-specific spectroscopic approach opens the door to understanding engineered materials with multiple metal centres and strong entanglement.
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Affiliation(s)
- Shiyu Fan
- Department of Physics and Astronomy, University of Tennessee, Knoxville, TN, 37996, USA
| | - Hena Das
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, 14853, USA
- Laboratory for Materials and Structures, Tokyo Institute of Technology, Midori-ku, 4259 Nagatesuta, Yokohama, Kanagawa, 226-8503, Japan
- Tokyo Tech World Research Hub Initiative, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama, Kanagawa, 226-8503, Japan
| | - Alejandro Rébola
- Instituto de Física Rosario-CONICET, Boulevard 27 de Febrero 210 bis, 2000, Rosario, Argentina
| | - Kevin A Smith
- Department of Chemistry, University of Tennessee, Knoxville, TN, 37996, USA
| | - Julia Mundy
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, 14853, USA
- Department of Physics, Harvard University, Cambridge, MA, 02138, USA
| | - Charles Brooks
- Department of Materials Science and Engineering, Cornell University, Ithaca, NY, 14853, USA
| | - Megan E Holtz
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, 14853, USA
- Department of Materials Science and Engineering, Cornell University, Ithaca, NY, 14853, USA
| | - David A Muller
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, 14853, USA
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, NY, 14853, USA
| | - Craig J Fennie
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, 14853, USA
| | - Ramamoorthy Ramesh
- Department of Materials Science and Engineering, University of California, Berkeley, CA, 94720, USA
- Department of Physics, University of California, Berkeley, CA, 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Darrell G Schlom
- Department of Materials Science and Engineering, Cornell University, Ithaca, NY, 14853, USA
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, NY, 14853, USA
| | - Stephen McGill
- National High Magnetic Field Laboratory, Tallahassee, FL, 32310, USA
| | - Janice L Musfeldt
- Department of Physics and Astronomy, University of Tennessee, Knoxville, TN, 37996, USA.
- Department of Chemistry, University of Tennessee, Knoxville, TN, 37996, USA.
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13
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Barrozo P, Småbråten DR, Tang YL, Prasad B, Saremi S, Ozgur R, Thakare V, Steinhardt RA, Holtz ME, Stoica VA, Martin LW, Schlom DG, Selbach SM, Ramesh R. Defect-Enhanced Polarization Switching in the Improper Ferroelectric LuFeO 3. Adv Mater 2020; 32:e2000508. [PMID: 32346899 DOI: 10.1002/adma.202000508] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2020] [Revised: 03/15/2020] [Accepted: 03/24/2020] [Indexed: 06/11/2023]
Abstract
Results of switching behavior of the improper ferroelectric LuFeO3 are presented. Using a model set of films prepared under controlled chemical and growth-rate conditions, it is shown that defects can reduce the quasi-static switching voltage by up to 40% in qualitative agreement with first-principles calculations. Switching studies show that the coercive field has a stronger frequency dispersion for the improper ferroelectrics compared to a proper ferroelectric such as PbTiO3 . It is concluded that the primary structural order parameter controls the switching dynamics of such improper ferroelectrics.
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Affiliation(s)
- Petrucio Barrozo
- Physics Department, Federal University of Sergipe, São Cristóvão, Sergipe, 49100-000, Brazil
- Department of Materials Science and Engineering and Department of Physics, University of California, Berkeley, CA, 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Didrik René Småbråten
- Department of Materials Science and Engineering, NTNU Norwegian University of Science and Technology, Norway
| | - Yun-Long Tang
- Department of Materials Science and Engineering and Department of Physics, University of California, Berkeley, CA, 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Bhagwati Prasad
- Department of Materials Science and Engineering and Department of Physics, University of California, Berkeley, CA, 94720, USA
| | - Sahar Saremi
- Department of Materials Science and Engineering and Department of Physics, University of California, Berkeley, CA, 94720, USA
| | - Rustem Ozgur
- Department of Materials Science and Engineering and Department of Physics, University of California, Berkeley, CA, 94720, USA
| | - Vishal Thakare
- Department of Materials Science and Engineering and Department of Physics, University of California, Berkeley, CA, 94720, USA
| | - Rachel A Steinhardt
- Department of Materials Science and Engineering, Cornell University, Ithaca, NY, 15805, USA
| | - Megan E Holtz
- Department of Materials Science and Engineering, Cornell University, Ithaca, NY, 15805, USA
| | - Vladimir Alexandru Stoica
- Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA, 16802, USA
| | - Lane W Martin
- Department of Materials Science and Engineering and Department of Physics, University of California, Berkeley, CA, 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Darrel G Schlom
- Department of Materials Science and Engineering, Cornell University, Ithaca, NY, 15805, USA
| | - Sverre Magnus Selbach
- Department of Materials Science and Engineering, NTNU Norwegian University of Science and Technology, Norway
| | - Ramamoorthy Ramesh
- Department of Materials Science and Engineering and Department of Physics, University of California, Berkeley, CA, 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
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14
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Padgett E, Holtz ME, Cueva P, Shao YT, Langenberg E, Schlom DG, Muller DA. The exit-wave power-cepstrum transform for scanning nanobeam electron diffraction: robust strain mapping at subnanometer resolution and subpicometer precision. Ultramicroscopy 2020; 214:112994. [PMID: 32413681 DOI: 10.1016/j.ultramic.2020.112994] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2019] [Revised: 03/01/2020] [Accepted: 04/04/2020] [Indexed: 10/24/2022]
Abstract
Scanning nanobeam electron diffraction (NBED) with fast pixelated detectors is a valuable technique for rapid, spatially resolved mapping of lattice structure over a wide range of length scales. However, intensity variations caused by dynamical diffraction and sample mistilts can hinder the measurement of diffracted disk centers as necessary for quantification. Robust data processing techniques are needed to provide accurate and precise measurements for complex samples and non-ideal conditions. Here we present an approach to address these challenges using a transform, called the exit wave power cepstrum (EWPC), inspired by cepstral analysis in audio signal processing. The EWPC transforms NBED patterns into real-space patterns with sharp peaks corresponding to inter-atomic spacings. We describe a simple analytical model for interpretation of these patterns that cleanly decouples lattice information from the intensity variations in NBED patterns caused by tilt and thickness. By tracking the inter-atomic spacing peaks in EWPC patterns, strain mapping is demonstrated for two practical applications: mapping of ferroelectric domains in epitaxially strained PbTiO3 films and mapping of strain profiles in arbitrarily oriented core-shell Pt-Co nanoparticle fuel-cell catalysts. The EWPC transform enables lattice structure measurement at sub-pm precision and sub-nm resolution that is robust to small sample mistilts and random orientations.
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Affiliation(s)
- Elliot Padgett
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, United States
| | - Megan E Holtz
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, United States; Department of Materials Science and Engineering, Cornell University, Ithaca, NY 14853, United States
| | - Paul Cueva
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, United States
| | - Yu-Tsun Shao
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, United States
| | - Eric Langenberg
- Department of Materials Science and Engineering, Cornell University, Ithaca, NY 14853, United States
| | - Darrell G Schlom
- Department of Materials Science and Engineering, Cornell University, Ithaca, NY 14853, United States; Kavli Institute at Cornell for Nanoscale Science, Ithaca, NY 14853, United States
| | - David A Muller
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, United States; Kavli Institute at Cornell for Nanoscale Science, Ithaca, NY 14853, United States.
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15
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Dawley NM, Marksz EJ, Hagerstrom AM, Olsen GH, Holtz ME, Goian V, Kadlec C, Zhang J, Lu X, Drisko JA, Uecker R, Ganschow S, Long CJ, Booth JC, Kamba S, Fennie CJ, Muller DA, Orloff ND, Schlom DG. Targeted chemical pressure yields tuneable millimetre-wave dielectric. Nat Mater 2020; 19:176-181. [PMID: 31873229 DOI: 10.1038/s41563-019-0564-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Accepted: 11/12/2019] [Indexed: 05/28/2023]
Abstract
Epitaxial strain can unlock enhanced properties in oxide materials, but restricts substrate choice and maximum film thickness, above which lattice relaxation and property degradation occur. Here we employ a chemical alternative to epitaxial strain by providing targeted chemical pressure, distinct from random doping, to induce a ferroelectric instability with the strategic introduction of barium into today's best millimetre-wave tuneable dielectric, the epitaxially strained 50-nm-thick n = 6 (SrTiO3)nSrO Ruddlesden-Popper dielectric grown on (110) DyScO3. The defect mitigating nature of (SrTiO3)nSrO results in unprecedented low loss at frequencies up to 125 GHz. No barium-containing Ruddlesden-Popper titanates are known, but the resulting atomically engineered superlattice material, (SrTiO3)n-m(BaTiO3)mSrO, enables low-loss, tuneable dielectric properties to be achieved with lower epitaxial strain and a 200% improvement in the figure of merit at commercially relevant millimetre-wave frequencies. As tuneable dielectrics are key constituents of emerging millimetre-wave high-frequency devices in telecommunications, our findings could lead to higher performance adaptive and reconfigurable electronics at these frequencies.
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Affiliation(s)
- Natalie M Dawley
- Department of Materials Science and Engineering, Cornell University, Ithaca, NY, USA
| | - Eric J Marksz
- Department of Materials Science and Engineering, University of Maryland, College Park, MD, USA
- National Institute of Standards and Technology, Boulder, CO, USA
| | | | - Gerhard H Olsen
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA
| | - Megan E Holtz
- Department of Materials Science and Engineering, Cornell University, Ithaca, NY, USA
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA
| | | | | | - Jingshu Zhang
- Department of Materials Science and Engineering, Cornell University, Ithaca, NY, USA
| | - Xifeng Lu
- National Institute of Standards and Technology, Boulder, CO, USA
| | - Jasper A Drisko
- National Institute of Standards and Technology, Boulder, CO, USA
| | | | | | - Christian J Long
- National Institute of Standards and Technology, Boulder, CO, USA
| | - James C Booth
- National Institute of Standards and Technology, Boulder, CO, USA
| | | | - Craig J Fennie
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA
| | - David A Muller
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA
| | - Nathan D Orloff
- National Institute of Standards and Technology, Boulder, CO, USA
| | - Darrell G Schlom
- Department of Materials Science and Engineering, Cornell University, Ithaca, NY, USA.
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, NY, USA.
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16
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Langenberg E, Saha D, Holtz ME, Wang JJ, Bugallo D, Ferreiro-Vila E, Paik H, Hanke I, Ganschow S, Muller DA, Chen LQ, Catalan G, Domingo N, Malen J, Schlom DG, Rivadulla F. Ferroelectric Domain Walls in PbTiO 3 Are Effective Regulators of Heat Flow at Room Temperature. Nano Lett 2019; 19:7901-7907. [PMID: 31596599 DOI: 10.1021/acs.nanolett.9b02991] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Achieving efficient spatial modulation of phonon transmission is an essential step on the path to phononic circuits using "phonon currents". With their intrinsic and reconfigurable interfaces, domain walls (DWs), ferroelectrics are alluring candidates to be harnessed as dynamic heat modulators. This paper reports the thermal conductivity of single-crystal PbTiO3 thin films over a wide variety of epitaxial-strain-engineered ferroelectric domain configurations. The phonon transport is proved to be strongly affected by the density and type of DWs, achieving a 61% reduction of the room-temperature thermal conductivity compared to the single-domain scenario. The thermal resistance across the ferroelectric DWs is obtained, revealing a very high value (≈5.0 × 10-9 K m2 W-1), comparable to grain boundaries in oxides, explaining the strong modulation of the thermal conductivity in PbTiO3. This low thermal conductance of the DWs is ascribed to the structural mismatch and polarization gradient found between the different types of domains in the PbTiO3 films, resulting in a structural inhomogeneity that extends several unit cells around the DWs. These findings demonstrate the potential of ferroelectric DWs as efficient regulators of heat flow in one single material, overcoming the complexity of multilayers systems and the uncontrolled distribution of grain boundaries, paving the way for applications in phononics.
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Affiliation(s)
- Eric Langenberg
- Department of Materials Science and Engineering , Cornell University , Ithaca , New York 14853 , United States
- Centro Singular de Investigación en Quı́mica Biolıoxica e Materiais Moleculares (CiQUS), Departmento de Quı́mica-Fı́sica , Universidade de Santiago de Compostela , Santiago de Compostela 15782 , Spain
| | - Dipanjan Saha
- Mechanical Engineering Department , Carnegie Mellon University , Pittsburgh , Pennsylvania 15213 , United States
| | - Megan E Holtz
- Department of Materials Science and Engineering , Cornell University , Ithaca , New York 14853 , United States
- School of Applied and Engineering Physics , Cornell University , Ithaca , New York 14853 , United States
| | - Jian-Jun Wang
- Department of Materials Science and Engineering , Pennsylvania State University , State College , Pennsylvania 16802 , United States
| | - David Bugallo
- Centro Singular de Investigación en Quı́mica Biolıoxica e Materiais Moleculares (CiQUS), Departmento de Quı́mica-Fı́sica , Universidade de Santiago de Compostela , Santiago de Compostela 15782 , Spain
| | - Elias Ferreiro-Vila
- Centro Singular de Investigación en Quı́mica Biolıoxica e Materiais Moleculares (CiQUS), Departmento de Quı́mica-Fı́sica , Universidade de Santiago de Compostela , Santiago de Compostela 15782 , Spain
| | - Hanjong Paik
- Department of Materials Science and Engineering , Cornell University , Ithaca , New York 14853 , United States
| | - Isabelle Hanke
- Leibniz-Institut für Kristallzüchtung , Max-Born-Straße 2 , 12489 Berlin , Germany
| | - Steffen Ganschow
- Leibniz-Institut für Kristallzüchtung , Max-Born-Straße 2 , 12489 Berlin , Germany
| | - David A Muller
- School of Applied and Engineering Physics , Cornell University , Ithaca , New York 14853 , United States
| | - Long-Qing Chen
- Department of Materials Science and Engineering , Pennsylvania State University , State College , Pennsylvania 16802 , United States
| | - Gustau Catalan
- CSIC, Barcelona Institute of Science and Technology, Campus Universitat Autònoma de Barcelona , Catalan Institute of Nanoscience and Nanotechnology (ICN2) , 08193 Bellaterra , Spain
| | - Neus Domingo
- CSIC, Barcelona Institute of Science and Technology, Campus Universitat Autònoma de Barcelona , Catalan Institute of Nanoscience and Nanotechnology (ICN2) , 08193 Bellaterra , Spain
| | - Jonathan Malen
- Mechanical Engineering Department , Carnegie Mellon University , Pittsburgh , Pennsylvania 15213 , United States
| | - Darrell G Schlom
- Department of Materials Science and Engineering , Cornell University , Ithaca , New York 14853 , United States
- Kavli Institute at Cornell for Nanoscale Science , Ithaca , New York 14853 , United States
| | - Francisco Rivadulla
- Centro Singular de Investigación en Quı́mica Biolıoxica e Materiais Moleculares (CiQUS), Departmento de Quı́mica-Fı́sica , Universidade de Santiago de Compostela , Santiago de Compostela 15782 , Spain
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17
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Schaab J, Skjærvø SH, Krohns S, Dai X, Holtz ME, Cano A, Lilienblum M, Yan Z, Bourret E, Muller DA, Fiebig M, Selbach SM, Meier D. Electrical half-wave rectification at ferroelectric domain walls. Nat Nanotechnol 2018; 13:1028-1034. [PMID: 30201990 DOI: 10.1038/s41565-018-0253-5] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Accepted: 08/02/2018] [Indexed: 06/08/2023]
Abstract
Domain walls in ferroelectric semiconductors show promise as multifunctional two-dimensional elements for next-generation nanotechnology. Electric fields, for example, can control the direct-current resistance and reversibly switch between insulating and conductive domain-wall states, enabling elementary electronic devices such as gates and transistors. To facilitate electrical signal processing and transformation at the domain-wall level, however, an expansion into the realm of alternating-current technology is required. Here, we demonstrate diode-like alternating-to-direct current conversion based on neutral ferroelectric domain walls in ErMnO3. By combining scanning probe and dielectric spectroscopy, we show that the rectification occurs at the tip-wall contact for frequencies at which the walls are effectively pinned. Using density functional theory, we attribute the responsible transport behaviour at the neutral walls to an accumulation of oxygen defects. The practical frequency regime and magnitude of the direct current output are controlled by the bulk conductivity, establishing electrode-wall junctions as versatile atomic-scale diodes.
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Affiliation(s)
- Jakob Schaab
- Department of Materials, ETH Zurich, Zurich, Switzerland
| | - Sandra H Skjærvø
- Department of Materials Science and Engineering, Norwegian University of Science and Technology (NTNU), Trondheim, Norway
| | - Stephan Krohns
- Experimental Physics V, University of Augsburg, Augsburg, Germany
| | - Xiaoyu Dai
- Department of Materials, ETH Zurich, Zurich, Switzerland
| | - Megan E Holtz
- School of Applied and Engineering Physics, Department of Physics, Cornell University, Ithaca, NY, USA
| | - Andrés Cano
- Department of Materials, ETH Zurich, Zurich, Switzerland
- Institut Néel, CNRS & University Grenoble Alpes, Grenoble, France
| | | | - Zewu Yan
- Department of Physics, ETH Zurich, Zurich, Switzerland
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Edith Bourret
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - David A Muller
- School of Applied and Engineering Physics, Department of Physics, Cornell University, Ithaca, NY, USA
- Kavli Institute at Cornell for Nanoscale Science Cornell University, Ithaca, NY, USA
| | - Manfred Fiebig
- Department of Materials, ETH Zurich, Zurich, Switzerland
| | - Sverre M Selbach
- Department of Materials Science and Engineering, Norwegian University of Science and Technology (NTNU), Trondheim, Norway
| | - Dennis Meier
- Department of Materials, ETH Zurich, Zurich, Switzerland.
- Department of Materials Science and Engineering, Norwegian University of Science and Technology (NTNU), Trondheim, Norway.
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18
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Chen Z, Chen Z, Liu ZQ, Holtz ME, Li CJ, Wang XR, Lü WM, Motapothula M, Fan LS, Turcaud JA, Dedon LR, Frederick C, Xu RJ, Gao R, N'Diaye AT, Arenholz E, Mundy JA, Venkatesan T, Muller DA, Wang LW, Liu J, Martin LW. Electron Accumulation and Emergent Magnetism in LaMnO_{3}/SrTiO_{3} Heterostructures. Phys Rev Lett 2017; 119:156801. [PMID: 29077457 DOI: 10.1103/physrevlett.119.156801] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Indexed: 06/07/2023]
Abstract
Emergent phenomena at polar-nonpolar oxide interfaces have been studied intensely in pursuit of next-generation oxide electronics and spintronics. Here we report the disentanglement of critical thicknesses for electron reconstruction and the emergence of ferromagnetism in polar-mismatched LaMnO_{3}/SrTiO_{3} (001) heterostructures. Using a combination of element-specific x-ray absorption spectroscopy and dichroism, and first-principles calculations, interfacial electron accumulation, and ferromagnetism have been observed within the polar, antiferromagnetic insulator LaMnO_{3}. Our results show that the critical thickness for the onset of electron accumulation is as thin as 2 unit cells (UC), significantly thinner than the observed critical thickness for ferromagnetism of 5 UC. The absence of ferromagnetism below 5 UC is likely induced by electron overaccumulation. In turn, by controlling the doping of the LaMnO_{3}, we are able to neutralize the excessive electrons from the polar mismatch in ultrathin LaMnO_{3} films and thus enable ferromagnetism in films as thin as 3 UC, extending the limits of our ability to synthesize and tailor emergent phenomena at interfaces and demonstrating manipulation of the electronic and magnetic structures of materials at the shortest length scales.
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Affiliation(s)
- Zuhuang Chen
- Department of Materials Science and Engineering, University of California, Berkeley, California 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Zhanghui Chen
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Z Q Liu
- School of Materials Science and Engineering, Beihang University, Beijing 100191, China
| | - M E Holtz
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA
| | - C J Li
- Department of Materials Science and Engineering, National University of Singapore, Singapore 117575, Singapore
- NUSNNI-Nanocore, National University of Singapore, Singapore 117411, Singapore
| | - X Renshaw Wang
- School of Physical and Mathematical Sciences & School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 637371, Singapore
| | - W M Lü
- Condensed Matter Science and Technology Institute, School of Science, Harbin Institute of Technology, Harbin 150081, People's Republic of China
| | - M Motapothula
- NUSNNI-Nanocore, National University of Singapore, Singapore 117411, Singapore
| | - L S Fan
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - J A Turcaud
- Department of Materials Science and Engineering, University of California, Berkeley, California 94720, USA
| | - L R Dedon
- Department of Materials Science and Engineering, University of California, Berkeley, California 94720, USA
| | - C Frederick
- Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA
| | - R J Xu
- Department of Materials Science and Engineering, University of California, Berkeley, California 94720, USA
| | - R Gao
- Department of Materials Science and Engineering, University of California, Berkeley, California 94720, USA
| | - A T N'Diaye
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - E Arenholz
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - J A Mundy
- Department of Materials Science and Engineering, University of California, Berkeley, California 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - T Venkatesan
- Department of Materials Science and Engineering, National University of Singapore, Singapore 117575, Singapore
- NUSNNI-Nanocore, National University of Singapore, Singapore 117411, Singapore
| | - D A Muller
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA
| | - L-W Wang
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Jian Liu
- Department of Materials Science and Engineering, University of California, Berkeley, California 94720, USA
| | - L W Martin
- Department of Materials Science and Engineering, University of California, Berkeley, California 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
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19
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Holtz ME, Shapovalov K, Mundy JA, Chang CS, Yan Z, Bourret E, Muller DA, Meier D, Cano A. Topological Defects in Hexagonal Manganites: Inner Structure and Emergent Electrostatics. Nano Lett 2017; 17:5883-5890. [PMID: 28872318 DOI: 10.1021/acs.nanolett.7b01288] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Diverse topological defects arise in hexagonal manganites, such as ferroelectric vortices, as well as neutral and charged domain walls. The topological defects are intriguing because their low symmetry enables unusual couplings between structural, charge, and spin degrees of freedom, holding great potential for novel types of functional 2D and 1D systems. Despite the considerable advances in analyzing the different topological defects in hexagonal manganites, the understanding of their key intrinsic properties is still rather limited and disconnected. In particular, a rapidly increasing number of structural variants is reported without clarifying their relation, leading to a zoo of seemingly unrelated topological textures. Here, we combine picometer-precise scanning-transmission-electron microscopy with Landau theory modeling to clarify the inner structure of topological defects in Er1-xZrxMnO3. By performing a comprehensive parametrization of the inner atomic defect structure, we demonstrate that one primary length scale drives the morphology of both vortices and domain walls. Our findings lead to a unifying general picture of this type of structural topological defects. We further derive novel fundamental and universal properties, such as unusual bound-charge distributions and electrostatics at the ferroelectric vortex cores with emergent U(1) symmetry.
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Affiliation(s)
| | | | - Julia A Mundy
- Department of Material Science and Engineering, University of California, Berkeley , Berkeley, California 94720, United States
| | | | - Zewu Yan
- Department of Physics, ETH Zürich , CH-8093 Zurich, Switzerland
- Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States
| | - Edith Bourret
- Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States
| | - David A Muller
- Kavli Institute at Cornell for Nanoscale Science , Ithaca, New York 14853, United States
| | - Dennis Meier
- Department of Materials Science and Engineering, Norwegian University of Science and Technology , 7491 Trondheim, Norway
| | - Andrés Cano
- CNRS, Université de Bordeaux, ICMCB , UPR 9048, 33600 Pessac, France
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Mundy JA, Schaab J, Kumagai Y, Cano A, Stengel M, Krug IP, Gottlob DM, Dog Anay H, Holtz ME, Held R, Yan Z, Bourret E, Schneider CM, Schlom DG, Muller DA, Ramesh R, Spaldin NA, Meier D. Functional electronic inversion layers at ferroelectric domain walls. Nat Mater 2017; 16:622-627. [PMID: 28319611 DOI: 10.1038/nmat4878] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Accepted: 02/06/2017] [Indexed: 06/06/2023]
Abstract
Ferroelectric domain walls hold great promise as functional two-dimensional materials because of their unusual electronic properties. Particularly intriguing are the so-called charged walls where a polarity mismatch causes local, diverging electrostatic potentials requiring charge compensation and hence a change in the electronic structure. These walls can exhibit significantly enhanced conductivity and serve as a circuit path. The development of all-domain-wall devices, however, also requires walls with controllable output to emulate electronic nano-components such as diodes and transistors. Here we demonstrate electric-field control of the electronic transport at ferroelectric domain walls. We reversibly switch from resistive to conductive behaviour at charged walls in semiconducting ErMnO3. We relate the transition to the formation-and eventual activation-of an inversion layer that acts as the channel for the charge transport. The findings provide new insight into the domain-wall physics in ferroelectrics and foreshadow the possibility to design elementary digital devices for all-domain-wall circuitry.
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Affiliation(s)
- J A Mundy
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA
| | - J Schaab
- Department of Materials, ETH Zurich, 8093 Zürich, Switzerland
| | - Y Kumagai
- Department of Materials, ETH Zurich, 8093 Zürich, Switzerland
| | - A Cano
- CNRS, Université de Bordeaux, ICMCB, UPR 9048, 33600 Pessac, France
| | - M Stengel
- ICREA-Institució Catalana de Recerca i Estudis Avançats, 08010 Barcelona, Spain
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, 08193 Bellaterra, Spain
| | - I P Krug
- Institut für Optik und Atomare Physik, TU Berlin, 10623 Berlin, Germany
| | - D M Gottlob
- Peter Grünberg Institute (PGI-6), Forschungszentrum Jülich, 52425 Jülich, Germany
| | - H Dog Anay
- Peter Grünberg Institute (PGI-6), Forschungszentrum Jülich, 52425 Jülich, Germany
| | - M E Holtz
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA
| | - R Held
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA
| | - Z Yan
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
- Department of Physics, ETH Zurich, Otto-Stern-Weg 1, 8093 Zürich, Switzerland
| | - E Bourret
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - C M Schneider
- Peter Grünberg Institute (PGI-6), Forschungszentrum Jülich, 52425 Jülich, Germany
| | - D G Schlom
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853, USA
| | - D A Muller
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853, USA
| | - R Ramesh
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
- Department of Materials Science and Engineering and Department of Physics, UC Berkeley, Berkeley, California 94720, USA
| | - N A Spaldin
- Department of Materials, ETH Zurich, 8093 Zürich, Switzerland
| | - D Meier
- Department of Materials, ETH Zurich, 8093 Zürich, Switzerland
- Department of Materials Science and Engineering, Norwegian University of Science and Technology, 7491 Trondheim, Norway
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Mundy JA, Brooks CM, Holtz ME, Moyer JA, Das H, Rébola AF, Heron JT, Clarkson JD, Disseler SM, Liu Z, Farhan A, Held R, Hovden R, Padgett E, Mao Q, Paik H, Misra R, Kourkoutis LF, Arenholz E, Scholl A, Borchers JA, Ratcliff WD, Ramesh R, Fennie CJ, Schiffer P, Muller DA, Schlom DG. Atomically engineered ferroic layers yield a room-temperature magnetoelectric multiferroic. Nature 2016; 537:523-7. [DOI: 10.1038/nature19343] [Citation(s) in RCA: 240] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Accepted: 07/25/2016] [Indexed: 11/09/2022]
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Nguyen KX, Holtz ME, Richmond-Decker J, Muller DA. Spatial Resolution in Scanning Electron Microscopy and Scanning Transmission Electron Microscopy Without a Specimen Vacuum Chamber. Microsc Microanal 2016; 22:754-767. [PMID: 27452123 DOI: 10.1017/s1431927616011405] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
A long-standing goal of electron microscopy has been the high-resolution characterization of specimens in their native environment. However, electron optics require high vacuum to maintain an unscattered and focused probe, a challenge for specimens requiring atmospheric or liquid environments. Here, we use an electron-transparent window at the base of a scanning electron microscope's objective lens to separate column vacuum from the specimen, enabling imaging under ambient conditions, without a specimen vacuum chamber. We demonstrate in-air imaging of specimens at nanoscale resolution using backscattered scanning electron microscopy (airSEM) and scanning transmission electron microscopy. We explore resolution and contrast using Monte Carlo simulations and analytical models. We find that nanometer-scale resolution can be obtained at gas path lengths up to 400 μm, although contrast drops with increasing gas path length. As the electron-transparent window scatters considerably more than gas at our operating conditions, we observe that the densities and thicknesses of the electron-transparent window are the dominant limiting factors for image contrast at lower operating voltages. By enabling a variety of detector configurations, the airSEM is applicable to a wide range of environmental experiments including the imaging of hydrated biological specimens and in situ chemical and electrochemical processes.
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Affiliation(s)
- Kayla X Nguyen
- 1School of Applied and Engineering Physics,Cornell University,Ithaca,NY 14853,USA
| | - Megan E Holtz
- 1School of Applied and Engineering Physics,Cornell University,Ithaca,NY 14853,USA
| | | | - David A Muller
- 1School of Applied and Engineering Physics,Cornell University,Ithaca,NY 14853,USA
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23
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Disseler SM, Borchers JA, Brooks CM, Mundy JA, Moyer JA, Hillsberry DA, Thies EL, Tenne DA, Heron J, Holtz ME, Clarkson JD, Stiehl GM, Schiffer P, Muller DA, Schlom DG, Ratcliff WD. Magnetic structure and ordering of multiferroic hexagonal LuFeO_{3}. Phys Rev Lett 2015; 114:217602. [PMID: 26066458 DOI: 10.1103/physrevlett.114.217602] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Indexed: 06/04/2023]
Abstract
We report on the magnetic structure and ordering of hexagonal LuFeO_{3} films of variable thickness grown by molecular-beam epitaxy on YSZ (111) and Al_{2}O_{3} (0001) substrates. These crystalline films exhibit long-range structural uniformity dominated by the polar P6_{3}cm phase, which is responsible for the paraelectric to ferroelectric transition that occurs above 1000 K. Using bulk magnetometry and neutron diffraction, we find that the system orders into a ferromagnetically canted antiferromagnetic state via a single transition below 155 K regardless of film thickness, which is substantially lower than that previously reported in hexagonal LuFeO_{3} films. The symmetry of the magnetic structure in the ferroelectric state implies that this material is a strong candidate for linear magnetoelectric coupling and control of the ferromagnetic moment directly by an electric field.
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Affiliation(s)
- Steven M Disseler
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - Julie A Borchers
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - Charles M Brooks
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA
| | - Julia A Mundy
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA
| | - Jarrett A Moyer
- Department of Physics and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | | | - Eric L Thies
- Department of Physics, Boise State University, Boise, Idaho 83725, USA
| | - Dmitri A Tenne
- Department of Physics, Boise State University, Boise, Idaho 83725, USA
| | - John Heron
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA
| | - Megan E Holtz
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA
| | - James D Clarkson
- Department of Materials Science and Engineering, University of California, Berkeley, California 94720, USA
| | - Gregory M Stiehl
- Department of Physics, Cornell University, Ithaca, New York 14853, USA
| | - Peter Schiffer
- Department of Physics and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - David A Muller
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853, USA
| | - Darrell G Schlom
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853, USA
| | - William D Ratcliff
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
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Holtz ME, Yu Y, Gunceler D, Gao J, Sundararaman R, Schwarz KA, Arias TA, Abruña HD, Muller DA. Nanoscale imaging of lithium ion distribution during in situ operation of battery electrode and electrolyte. Nano Lett 2014; 14:1453-1459. [PMID: 24548177 DOI: 10.1021/nl404577c] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
A major challenge in the development of new battery materials is understanding their fundamental mechanisms of operation and degradation. Their microscopically inhomogeneous nature calls for characterization tools that provide operando and localized information from individual grains and particles. Here, we describe an approach that enables imaging the nanoscale distribution of ions during electrochemical charging of a battery in a transmission electron microscope liquid flow cell. We use valence energy-loss spectroscopy to track both solvated and intercalated ions, with electronic structure fingerprints of the solvated ions identified using an ab initio nonlinear response theory. Equipped with the new electrochemical cell holder, nanoscale spectroscopy and theory, we have been able to determine the lithiation state of a LiFePO4 electrode and surrounding aqueous electrolyte in real time with nanoscale resolution during electrochemical charge and discharge. We follow lithium transfer between electrode and electrolyte and image charging dynamics in the cathode. We observe competing delithiation mechanisms such as core-shell and anisotropic growth occurring in parallel for different particles under the same conditions. This technique represents a general approach for the operando nanoscale imaging of electrochemically active ions in the electrode and electrolyte in a wide range of electrical energy storage systems.
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Affiliation(s)
- Megan E Holtz
- School of Applied and Engineering Physics, Cornell University , Ithaca, New York 14853, United States
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Abstract
In situ scanning transmission electron microscopy (STEM) through liquids is a promising approach for exploring biological and materials processes. However, options for in situ chemical identification are limited: X-ray analysis is precluded because the liquid cell holder shadows the detector and electron energy-loss spectroscopy (EELS) is degraded by multiple scattering events in thick layers. Here, we explore the limits of EELS in the study of chemical reactions in their native environments in real time and on the nanometer scale. The determination of the local electron density, optical gap, and thickness of the liquid layer by valence EELS is demonstrated. By comparing theoretical and experimental plasmon energies, we find that liquids appear to follow the free-electron model that has been previously established for solids. Signals at energies below the optical gap and plasmon energy of the liquid provide a high signal-to-background ratio regime as demonstrated for LiFePO4 in an aqueous solution. The potential for the use of valence EELS to understand in situ STEM reactions is demonstrated for beam-induced deposition of metallic copper: as copper clusters grow, EELS develops low-loss peaks corresponding to metallic copper. From these techniques, in situ imaging and valence EELS offer insights into the local electronic structure of nanoparticles and chemical reactions.
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Affiliation(s)
- Megan E Holtz
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14850, USA.
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