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Co-emergence of magnetic order and structural fluctuations in magnetite. Nat Commun 2019; 10:2857. [PMID: 31253806 PMCID: PMC6599026 DOI: 10.1038/s41467-019-10949-9] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Accepted: 06/10/2019] [Indexed: 11/09/2022] Open
Abstract
The nature of the Verwey transition occurring at TV ≈ 125 K in magnetite (Fe3O4) has been an outstanding problem over many decades. A complex low temperature electronic order was recently discovered and associated structural fluctuations persisting above TV are widely reported, but the origin of the underlying correlations and hence of the Verwey transition remains unclear. Here we show that local structural fluctuations in magnetite emerge below the Curie transition at TC ≈ 850 K, through X-ray pair distribution function analysis. Around 80% of the low temperature correlations emerge in proportion to magnetization below TC. This confirms that fluctuations in Fe-Fe bonding arising from magnetic order are the primary electronic instability and hence the origin of the Verwey transition. Such hidden instabilities may be important to other spin-polarised conductors and orbitally degenerate materials.
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Reeves KG, Kanai Y. Theoretical oxidation state analysis of Ru-(bpy)3: influence of water solvation and Hubbard correction in first-principles calculations. J Chem Phys 2014; 141:024305. [PMID: 25028017 DOI: 10.1063/1.4886406] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Oxidation state is a powerful concept that is widely used in chemistry and materials physics, although the concept itself is arguably ill-defined quantum mechanically. In this work, we present impartial comparison of four, well-recognized theoretical approaches based on Lowdin atomic orbital projection, Bader decomposition, maximally localized Wannier function, and occupation matrix diagonalization, for assessing how well transition metal oxidation states can be characterized. Here, we study a representative molecular complex, tris(bipyridine)ruthenium. We also consider the influence of water solvation through first-principles molecular dynamics as well as the improved electronic structure description for strongly correlated d-electrons by including Hubbard correction in density functional theory calculations.
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Affiliation(s)
- Kyle G Reeves
- Department of Chemistry, University of North Carolina at Chapel Hill, North Carolina 27599-3290, USA
| | - Yosuke Kanai
- Department of Chemistry, University of North Carolina at Chapel Hill, North Carolina 27599-3290, USA
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de Groot J, Mueller T, Rosenberg RA, Keavney DJ, Islam Z, Kim JW, Angst M. Charge order in LuFe2O4: an unlikely route to ferroelectricity. PHYSICAL REVIEW LETTERS 2012; 108:187601. [PMID: 22681119 DOI: 10.1103/physrevlett.108.187601] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Indexed: 06/01/2023]
Abstract
We present the refinement of the crystal structure of charge-ordered LuFe2O4, based on single-crystal x-ray diffraction data. The arrangement of the different Fe-valence states, determined with bond-valence-sum analysis, corresponds to a stacking of charged Fe bilayers, in contrast with the polar bilayers previously suggested. This arrangement is supported by an analysis of x-ray magnetic circular dichroism spectra, which also evidences a strong charge-spin coupling. The nonpolar bilayers are inconsistent with charge order based ferroelectricity.
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Affiliation(s)
- J de Groot
- Peter Grünberg Institut PGI and Jülich Centre for Neutron Science JCNS, JARA-FIT, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
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Sit PHL, Car R, Cohen MH, Selloni A. Simple, Unambiguous Theoretical Approach to Oxidation State Determination via First-Principles Calculations. Inorg Chem 2011; 50:10259-67. [DOI: 10.1021/ic2013107] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Patrick H.-L. Sit
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Roberto Car
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
- Princeton Institute for the Science and Technology of Materials, Princeton University, Princeton, New Jersey 08544, United States
| | - Morrel H. Cohen
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
- Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, United States
| | - Annabella Selloni
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
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Yang HX, Tian HF, Song YJ, Qin YB, Zhao YG, Ma C, Li JQ. Polar nanodomains and giant converse magnetoelectric effect in charge-ordered Fe2OBO3. PHYSICAL REVIEW LETTERS 2011; 106:016406. [PMID: 21231761 DOI: 10.1103/physrevlett.106.016406] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2010] [Indexed: 05/30/2023]
Abstract
The magnetoelectric coupling and polar nanodomains in the charge-ordered Fe2OBO3 have been extensively studied from room temperature down to 100 K. In situ TEM investigations demonstrate that the charge-ordering transition characterized by an incommensurate modulation could evidently result in remarkable polar nanodomains at low temperatures. This kind of nanodomain could play a critical role in triggering a high dielectric constant and notable dielectric dispersion as observed in Fe2OBO3. Moreover, measurements of the magnetoelectric coupling under electrical field demonstrate the existence of giant electrically induced changes in magnetization around the magnetic transition.
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Affiliation(s)
- H X Yang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
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Angst M, Hermann RP, Christianson AD, Lumsden MD, Lee C, Whangbo MH, Kim JW, Ryan PJ, Nagler SE, Tian W, Jin R, Sales BC, Mandrus D. Charge order in LuFe2O4: antiferroelectric ground state and coupling to magnetism. PHYSICAL REVIEW LETTERS 2008; 101:227601. [PMID: 19113522 DOI: 10.1103/physrevlett.101.227601] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2008] [Indexed: 05/27/2023]
Abstract
X-ray scattering by multiferroic LuFe2O4 is reported. Below 320 K, superstructure reflections indicate an incommensurate charge order with propagation close to (1/3 1/3 3/2). The corresponding charge configuration, also found by electronic structure calculations as most stable, contains polar Fe/O double layers with antiferroelectric stacking. Diffuse scattering at 360 K, with (1/3 1/3 0) propagation, indicates ferroelectric short-range correlations between neighboring double layers. The temperature dependence of the incommensuration indicates that charge order and magnetism are coupled.
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Affiliation(s)
- M Angst
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
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Raebiger H, Lany S, Zunger A. Charge self-regulation upon changing the oxidation state of transition metals in insulators. Nature 2008; 453:763-6. [PMID: 18528391 DOI: 10.1038/nature07009] [Citation(s) in RCA: 213] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2007] [Accepted: 04/14/2008] [Indexed: 11/09/2022]
Abstract
Transition-metal atoms embedded in an ionic or semiconducting crystal can exist in various oxidation states that have distinct signatures in X-ray photoemission spectroscopy and 'ionic radii' which vary with the oxidation state of the atom. These oxidation states are often tacitly associated with a physical ionization of the transition-metal atoms--that is, a literal transfer of charge to or from the atoms. Physical models have been founded on this charge-transfer paradigm, but first-principles quantum mechanical calculations show only negligible changes in the local transition-metal charge as the oxidation state is altered. Here we explain this peculiar tendency of transition-metal atoms to maintain a constant local charge under external perturbations in terms of an inherent, homeostasis-like negative feedback. We show that signatures of oxidation states and multivalence--such as X-ray photoemission core-level shifts, ionic radii and variations in local magnetization--that have often been interpreted as literal charge transfer are instead a consequence of the negative-feedback charge regulation.
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Affiliation(s)
- Hannes Raebiger
- National Renewable Energy Laboratory, Golden, Colorado 80401, USA.
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Hao X, Xu Y, Lv M, Zhou D, Wu Z, Meng J. Charge, Orbital, and Magnetic Ordering in YBaFe2O5 from First-Principles Calculations. Inorg Chem 2008; 47:4734-9. [DOI: 10.1021/ic800060c] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Xianfeng Hao
- Key Laboratory of Rare Earth Chemistry and Physics, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P.R. China, School of Biological Engineering, Changchun University of Technology, Changchun 130012, P.R. China, and Graduate School, Chinese Academy of Sciences, Beijing 100049, P.R. China
| | - Yuanhui Xu
- Key Laboratory of Rare Earth Chemistry and Physics, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P.R. China, School of Biological Engineering, Changchun University of Technology, Changchun 130012, P.R. China, and Graduate School, Chinese Academy of Sciences, Beijing 100049, P.R. China
| | - Minfeng Lv
- Key Laboratory of Rare Earth Chemistry and Physics, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P.R. China, School of Biological Engineering, Changchun University of Technology, Changchun 130012, P.R. China, and Graduate School, Chinese Academy of Sciences, Beijing 100049, P.R. China
| | - Defeng Zhou
- Key Laboratory of Rare Earth Chemistry and Physics, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P.R. China, School of Biological Engineering, Changchun University of Technology, Changchun 130012, P.R. China, and Graduate School, Chinese Academy of Sciences, Beijing 100049, P.R. China
| | - Zhijian Wu
- Key Laboratory of Rare Earth Chemistry and Physics, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P.R. China, School of Biological Engineering, Changchun University of Technology, Changchun 130012, P.R. China, and Graduate School, Chinese Academy of Sciences, Beijing 100049, P.R. China
| | - Jian Meng
- Key Laboratory of Rare Earth Chemistry and Physics, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P.R. China, School of Biological Engineering, Changchun University of Technology, Changchun 130012, P.R. China, and Graduate School, Chinese Academy of Sciences, Beijing 100049, P.R. China
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Angst M, Hermann RP, Schweika W, Kim JW, Khalifah P, Xiang HJ, Whangbo MH, Kim DH, Sales BC, Mandrus D. Incommensurate charge order phase in Fe2OBO3 due to geometrical frustration. PHYSICAL REVIEW LETTERS 2007; 99:256402. [PMID: 18233535 DOI: 10.1103/physrevlett.99.256402] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2007] [Indexed: 05/22/2023]
Abstract
The temperature dependence of charge order in Fe2OBO3 was investigated by resistivity and differential scanning calorimetry measurements, Mössbauer spectroscopy, and synchrotron x-ray scattering, revealing an intermediate phase between room temperature and 340 K, characterized by coexisting mobile and immobile carriers, and by incommensurate superstructure modulations with temperature-dependent propagation vector (1/2, 0, tau). The incommensurate modulations arise from specific antiphase boundaries with low energy cost due to geometrical charge frustration.
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Affiliation(s)
- M Angst
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
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