1
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Truc B, Usai P, Pennacchio F, Berruto G, Claude R, Madan I, Sala V, LaGrange T, Vanacore GM, Benhabib S, Carbone F. Ultrafast generation of hidden phases via energy-tuned electronic photoexcitation in magnetite. Proc Natl Acad Sci U S A 2024; 121:e2316438121. [PMID: 38900799 PMCID: PMC11214049 DOI: 10.1073/pnas.2316438121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Accepted: 04/26/2024] [Indexed: 06/22/2024] Open
Abstract
Phase transitions occurring in nonequilibrium conditions can evolve through high-energy intermediate states inaccessible via equilibrium adiabatic conditions. Because of the subtle nature of such hidden phases, their direct observation is extremely challenging and requires simultaneous visualization of matter at subpicoseconds and subpicometer scales. Here, we show that a magnetite crystal in the vicinity of its metal-to-insulator transition evolves through different hidden states when controlled via energy-tuned ultrashort laser pulses. By directly monitoring magnetite's crystal structure with ultrafast electron diffraction, we found that upon near-infrared (800 nm) excitation, the trimeron charge/orbital ordering pattern is destroyed in favor of a phase-separated state made of cubic-metallic and monoclinic-insulating regions. On the contrary, visible light (400 nm) activates a photodoping charge transfer process that further promotes the long-range order of the trimerons by stabilizing the charge density wave fluctuations, leading to the reinforcement of the monoclinic insulating phase. Our results demonstrate that magnetite's structure can evolve through completely different metastable hidden phases that can be reached long after the initial excitation has relaxed, breaking ground for a protocol to control emergent properties of matter.
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Affiliation(s)
- B. Truc
- School of Basic Sciences, Institute of Physics, Laboratory for Ultrafast Microscopy and Electron Scattering, École Polytechnique Fédérale de Lausanne, LausanneCH-1015, Switzerland
| | - P. Usai
- School of Basic Sciences, Institute of Physics, Laboratory for Ultrafast Microscopy and Electron Scattering, École Polytechnique Fédérale de Lausanne, LausanneCH-1015, Switzerland
| | - F. Pennacchio
- School of Basic Sciences, Institute of Physics, Laboratory for Ultrafast Microscopy and Electron Scattering, École Polytechnique Fédérale de Lausanne, LausanneCH-1015, Switzerland
| | - G. Berruto
- School of Basic Sciences, Institute of Physics, Laboratory for Ultrafast Microscopy and Electron Scattering, École Polytechnique Fédérale de Lausanne, LausanneCH-1015, Switzerland
| | - R. Claude
- School of Basic Sciences, Institute of Physics, Laboratory for Ultrafast Microscopy and Electron Scattering, École Polytechnique Fédérale de Lausanne, LausanneCH-1015, Switzerland
| | - I. Madan
- School of Basic Sciences, Institute of Physics, Laboratory for Ultrafast Microscopy and Electron Scattering, École Polytechnique Fédérale de Lausanne, LausanneCH-1015, Switzerland
| | - V. Sala
- Dipartimento di Fisica, Politecnico di Milano, Milano20133, Italy
| | - T. LaGrange
- School of Basic Sciences, Institute of Physics, Laboratory for Ultrafast Microscopy and Electron Scattering, École Polytechnique Fédérale de Lausanne, LausanneCH-1015, Switzerland
| | - G. M. Vanacore
- School of Basic Sciences, Institute of Physics, Laboratory for Ultrafast Microscopy and Electron Scattering, École Polytechnique Fédérale de Lausanne, LausanneCH-1015, Switzerland
- Department of Materials Science, Laboratory of Ultrafast Microscopy for Nanoscale Dynamics, University of Milano-Bicocca, Milan20125, Italy
| | - S. Benhabib
- School of Basic Sciences, Institute of Physics, Laboratory for Ultrafast Microscopy and Electron Scattering, École Polytechnique Fédérale de Lausanne, LausanneCH-1015, Switzerland
- Centre national de la recherche scientifique, Laboratoire de Physique des Solides, Université Paris-Saclay, Orsay91405, France
| | - F. Carbone
- School of Basic Sciences, Institute of Physics, Laboratory for Ultrafast Microscopy and Electron Scattering, École Polytechnique Fédérale de Lausanne, LausanneCH-1015, Switzerland
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2
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Wang X, Zhu W. A microscopic view of checkerboard and striped charge orders through doping antiferromagnetic Mott insulator. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2024; 36:265602. [PMID: 38518372 DOI: 10.1088/1361-648x/ad3709] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Accepted: 03/22/2024] [Indexed: 03/24/2024]
Abstract
The emergence of charge order in doped Mott insulators has received considerable attention due to its relevance to a variety of realistic materials and experiments. To investigate the interplay between magnetic and charge order, we have studied the semiclassical Kondo lattice model, which includes both electronic and magnetic degrees of freedom. By combining Langevin dynamical simulations with the kernel polynomial method, our results reveal the presence of charged stripe order, checkerboard order, and non-uniform charge disorder in the near-half-filling regime. Importantly, our simulations show that both the doping level and the strength of thes-dexchange coupling play a crucial role in facilitating charge order formation. These phases give rise to distinct electronic structures as well as excitations in the magnetic dynamics, providing insights into the underlying mechanism of charge ordering phenomena.
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Affiliation(s)
- Xuanlan Wang
- Department of Physics, Fudan University, Shanghai 200433, People's Republic of China
| | - Wei Zhu
- Key Laboratory for Quantum Materials of Zhejiang Province, School of Science, Westlake University, Hangzhou 310024, People's Republic of China
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3
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Layek S, Greenberg E, Chariton S, Bykov M, Bykova E, Trots DM, Kurnosov AV, Chuvashova I, Ovsyannikov SV, Leonov I, Rozenberg GK. Verwey-Type Charge Ordering and Site-Selective Mott Transition in Fe 4O 5 under Pressure. J Am Chem Soc 2022; 144:10259-10269. [PMID: 35649281 PMCID: PMC9204770 DOI: 10.1021/jacs.2c00895] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
![]()
The metal–insulator transition
driven by electronic correlations
is one of the most fundamental concepts in condensed matter. In mixed-valence
compounds, this transition is often accompanied by charge ordering
(CO), resulting in the emergence of complex phases and unusual behaviors.
The famous example is the archetypal mixed-valence mineral magnetite,
Fe3O4, exhibiting a complex charge-ordering
below the Verwey transition, whose nature has been a subject of long-time
debates. In our study, using high-resolution X-ray diffraction supplemented
by resistance measurements and DFT+DMFT calculations, the electronic,
magnetic, and structural properties of recently synthesized mixed-valence
Fe4O5 are investigated under pressure to ∼100
GPa. Our calculations, consistent with experiment, reveal that at
ambient conditions Fe4O5 is a narrow-gap insulator
characterized by the original Verwey-type CO. Under pressure Fe4O5 undergoes a series of electronic and magnetic-state
transitions with an unusual compressional behavior above ∼50
GPa. A site-dependent collapse of local magnetic moments is followed
by the site-selective insulator-to-metal transition at ∼84
GPa, occurring at the octahedral Fe sites. This phase transition is
accompanied by a 2+ to 3+ valence change of the prismatic Fe ions
and collapse of CO. We provide a microscopic explanation of the complex
charge ordering in Fe4O5 which “unifies”
it with the behavior of two archetypal examples of charge- or bond-ordered
materials, magnetite and rare-earth nickelates (RNiO3).
We find that at low temperatures the Verwey-type CO competes with
the “trimeron”/“dimeron” charge ordered
states, allowing for pressure/temperature tuning of charge ordering.
Summing up the available data, we present the pressure–temperature
phase diagram of Fe4O5.
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Affiliation(s)
- Samar Layek
- School of Physics and Astronomy, Tel Aviv University, 69978 Tel Aviv, Israel.,Department of Physics, School of Engineering, University of Petroleum and Energy Studies (UPES), Dehradun, Uttarakhand 248007, India
| | - Eran Greenberg
- Center for Advanced Radiation Sources, University of Chicago, 5640 South Ellis Avenue, 60637 Chicago, United States.,Applied Physics Division, Soreq NRC, Yavne, 81800, Israel
| | - Stella Chariton
- Center for Advanced Radiation Sources, University of Chicago, 5640 South Ellis Avenue, 60637 Chicago, United States
| | - Maxim Bykov
- Institute of Inorganic Chemistry, University of Cologne, Greinstrasse 6, 50939 Cologne, Germany
| | - Elena Bykova
- Earth and Planets Laboratory, Carnegie Institution for Science, Washington, District of Columbia 20015, United States.,Bayerisches Geoinstitut, Universität Bayreuth, Universitätsstrasse 30, D-95447 Bayreuth, Germany
| | - Dmytro M Trots
- Bayerisches Geoinstitut, Universität Bayreuth, Universitätsstrasse 30, D-95447 Bayreuth, Germany
| | - Alexander V Kurnosov
- Bayerisches Geoinstitut, Universität Bayreuth, Universitätsstrasse 30, D-95447 Bayreuth, Germany
| | - Irina Chuvashova
- Harvard Physics, Jefferson Physical Lab, 17 Oxford Street, Cambridge, Massachusetts 02138, United States.,Department of Chemistry and Biochemistry, Florida International University, 11200 SW Eighth Street, CP 234, Miami, Florida 33199, United States
| | - Sergey V Ovsyannikov
- Bayerisches Geoinstitut, Universität Bayreuth, Universitätsstrasse 30, D-95447 Bayreuth, Germany
| | - Ivan Leonov
- M. N. Miheev Institute of Metal Physics, Russian Academy of Sciences, 620108 Yekaterinburg, Russia.,Ural Federal University, 620002 Yekaterinburg, Russia.,Skolkovo Institute of Science and Technology, 143026 Moscow, Russia
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4
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Attfield JP. Magnetism and the Trimeron Bond. CHEMISTRY OF MATERIALS : A PUBLICATION OF THE AMERICAN CHEMICAL SOCIETY 2022; 34:2877-2885. [PMID: 35814039 PMCID: PMC9261838 DOI: 10.1021/acs.chemmater.2c00275] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Revised: 03/14/2022] [Indexed: 05/06/2023]
Abstract
A review of progress in understanding the Verwey transition in magnetite (Fe3O4) over the past decade is presented. This electronic and structural transition at T V ≈ 125 K was reported in 1939 and has since been a contentious issue in magnetism. Long range Fe2+/Fe3+ charge ordering has been confirmed below the transition from crystal structure refinement, and Fe2+ orbital ordering and formation of trimerons through weak bonding of Fe2+ states to two Fe neighbors has been discovered. This model has accounted for many spectroscopic observations such as the 57Fe NMR frequencies. The trimeron lifetime has been measured, and trimeron soft modes have been observed. The origin of the first to second order crossover of Verwey transitions in doped magnetites has been revealed by a nanoparticle study. Electronic and structural fluctuations are found to persist to temperatures far above T V and local structural distortions track the bulk magnetization, disappearing at the 850 K Curie transition. New binary mixed-valent iron oxides discovered at high pressure are found to have electronic transitions and orbital molecule ground states similar to those of magnetite.
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5
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Diaz-Lopez M, Guda SA, Joly Y. Crystal Orbital Overlap Population and X-ray Absorption Spectroscopy. J Phys Chem A 2020; 124:6111-6118. [PMID: 32551621 DOI: 10.1021/acs.jpca.0c04084] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We present an extension of an ab initio numerical tool calculating X-ray absorption spectroscopies and crystal orbital overlap populations at the same time. Density functional theory is used to calculate the electronic structure in both occupied (valence to core X-ray emission spectroscopy) and nonoccupied states (i.e., X-ray absorption near the edge structure and X-ray magnetic circular dichroism) and to evaluate the orbital overlap typifying the covalency between neighboring atoms. We show how the different features in the experimental spectra can be correlated to the chemical bonds around the absorbing atoms in several examples including acrylonitrile molecules, rutile TiO2, Li2RuO3 high-energy density cathode, ZnO, and anti-ferromagnetic V2O3.
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Affiliation(s)
- Maria Diaz-Lopez
- STFC Rutherford Appleton Laboratory, ISIS Facility, Didcot OX11 0QX, U.K.,Diamond Light Source Ltd., Diamond House, Harwell Science and Innovation Campus, Didcot OX11 0DE, U.K.,University Grenoble Alpes, CNRS, Grenoble INP, Institut Néel, Grenoble 38042, France
| | - Sergey A Guda
- The Smart Materials Research Center, Southern Federal University, Sladkova Street 174/28, Rostov-on-Don 344090, Russia.,Institute for Mathematics, Mechanics, and Computer Science, Southern Federal University, Rostov-on-Don 344090, Russia
| | - Yves Joly
- University Grenoble Alpes, CNRS, Grenoble INP, Institut Néel, Grenoble 38042, France
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6
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Heat capacity signature of frustrated trimerons in magnetite. Sci Rep 2020; 10:10909. [PMID: 32616822 PMCID: PMC7331697 DOI: 10.1038/s41598-020-67955-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Accepted: 05/28/2020] [Indexed: 11/08/2022] Open
Abstract
Recently it has been proposed that the long-range electronic order formed by trimerons in magnetite should be frustrated due to the great degeneracy of arrangements linking trimerons. This result has important consequences as charge ordering from the condensed minority band electrons leads to a complex 3D antiferro orbital order pattern. Further more, the corner sharing tetrahedra structure of spinel B-sites supports frustration for antiferromagnetic alignments. Therefore frustration due to competing interactions will itself induce disorder and very likely frustration in the spin orientations. Here we present very low temperature specific heat data that show two deviations to the magnons and phonons contributions, that we analyze in terms of Schottky-type anomalies. The first one is associated with the thermal activation across both ferroelastic twin and ferromagnetic anti-phase domains. The second Schottky-type anomaly displays an inverse (1/H) field dependence which is a direct indication of the disordered glassy network with macroscopically degenerated singular ground states.
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7
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Schmidt ME, Muruganathan M, Kanzaki T, Iwasaki T, Hammam AMM, Suzuki S, Ogawa S, Mizuta H. Dielectric-Screening Reduction-Induced Large Transport Gap in Suspended Sub-10 nm Graphene Nanoribbon Functional Devices. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2019; 15:e1903025. [PMID: 31573772 DOI: 10.1002/smll.201903025] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Revised: 08/15/2019] [Indexed: 06/10/2023]
Abstract
The predicted quasiparticle energy gap of more than 1 eV in sub-6 nm graphene nanoribbons (GNRs) is elusive, as it is strongly suppressed by the substrate dielectric screening. The number of techniques that can produce suspended high-quality and electrically contacted GNRs is small. The helium ion beam milling technique is capable of achieving sub-5 nm patterning; however, the functional device fabrication and the electrical characteristics are not yet reported. Here, the electrical transport measurement of suspended ≈6 nm wide mono- and bilayer GNR functional devices is reported, which are obtained through sub-nanometer resolution helium ion beam milling with controlled total helium ion budget. The transport gap opening of 0.16-0.8 eV is observed at room temperature. The measured transport gap of the different edge orientated GNRs is in good agreement with first-principles simulation results. The enhanced electron-electron interaction and reduced dielectric screening in the suspended quasi-1D GNRs and anti-ferromagnetic coupling between opposite edges in the zigzag GNRs substantiate the observed large transport gap.
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Affiliation(s)
- Marek E Schmidt
- School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa, 923-1292, Japan
| | - Manoharan Muruganathan
- School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa, 923-1292, Japan
| | - Teruhisa Kanzaki
- School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa, 923-1292, Japan
| | - Takuya Iwasaki
- School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa, 923-1292, Japan
| | - Ahmed M M Hammam
- School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa, 923-1292, Japan
- Physics Department, Faculty of Science, Minia University, 11432 Main Road-Shalaby Land, Minia, 61519, Egypt
| | - Shunei Suzuki
- School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa, 923-1292, Japan
| | - Shinichi Ogawa
- Nanoelectronics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 16-1 Onogawa, Tsukuba, 305-8569, Japan
| | - Hiroshi Mizuta
- School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa, 923-1292, Japan
- Hitachi Cambridge Laboratory, Hitachi Europe Ltd., J. J. Thomson Avenue, Cambridge, CB3 0HE, UK
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8
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Joly Y, Abisset A, Bailly A, De Santis M, Fettar F, Grenier S, Mannix D, Ramos AY, Saint-Lager MC, Soldo-Olivier Y, Tonnerre JM, Guda SA, Gründer Y. Simulation of Surface Resonant X-ray Diffraction. J Chem Theory Comput 2018; 14:973-980. [DOI: 10.1021/acs.jctc.7b01032] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Yves Joly
- Université Grenoble Alpes,
CNRS, Grenoble INP, Institut Néel, 38042 Grenoble, France
| | - Antoine Abisset
- Université Grenoble Alpes,
CNRS, Grenoble INP, Institut Néel, 38042 Grenoble, France
| | - Aude Bailly
- Université Grenoble Alpes,
CNRS, Grenoble INP, Institut Néel, 38042 Grenoble, France
| | - Maurizio De Santis
- Université Grenoble Alpes,
CNRS, Grenoble INP, Institut Néel, 38042 Grenoble, France
| | - Farid Fettar
- Université Grenoble Alpes,
CNRS, Grenoble INP, Institut Néel, 38042 Grenoble, France
| | - Stéphane Grenier
- Université Grenoble Alpes,
CNRS, Grenoble INP, Institut Néel, 38042 Grenoble, France
| | - Danny Mannix
- Université Grenoble Alpes,
CNRS, Grenoble INP, Institut Néel, 38042 Grenoble, France
| | - Aline Y. Ramos
- Université Grenoble Alpes,
CNRS, Grenoble INP, Institut Néel, 38042 Grenoble, France
| | | | - Yvonne Soldo-Olivier
- Université Grenoble Alpes,
CNRS, Grenoble INP, Institut Néel, 38042 Grenoble, France
| | - Jean-Marc Tonnerre
- Université Grenoble Alpes,
CNRS, Grenoble INP, Institut Néel, 38042 Grenoble, France
| | - Sergey A. Guda
- Institute for Mathematics, Mechanics, and Computer Science, Southern Federal University, 344090 Rostov-on-Don, Russia
| | - Yvonne Gründer
- Oliver Lodge Laboratory, Department of Physics, University of Liverpool, Liverpool L69 7ZE, United Kingdom
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9
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Huang HY, Chen ZY, Wang RP, de Groot FMF, Wu WB, Okamoto J, Chainani A, Singh A, Li ZY, Zhou JS, Jeng HT, Guo GY, Park JG, Tjeng LH, Chen CT, Huang DJ. Jahn-Teller distortion driven magnetic polarons in magnetite. Nat Commun 2017; 8:15929. [PMID: 28660878 PMCID: PMC5493765 DOI: 10.1038/ncomms15929] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2017] [Accepted: 05/12/2017] [Indexed: 11/20/2022] Open
Abstract
The first known magnetic mineral, magnetite, has unusual properties, which have fascinated mankind for centuries; it undergoes the Verwey transition around 120 K with an abrupt change in structure and electrical conductivity. The mechanism of the Verwey transition, however, remains contentious. Here we use resonant inelastic X-ray scattering over a wide temperature range across the Verwey transition to identify and separate out the magnetic excitations derived from nominal Fe2+ and Fe3+ states. Comparison of the experimental results with crystal-field multiplet calculations shows that the spin–orbital dd excitons of the Fe2+ sites arise from a tetragonal Jahn-Teller active polaronic distortion of the Fe2+O6 octahedra. These low-energy excitations, which get weakened for temperatures above 350 K but persist at least up to 550 K, are distinct from optical excitations and are best explained as magnetic polarons. The Verwey transition of magnetite is complex due to the coexistence of strong correlations and electron-phonon coupling. Here, the authors use resonant inelastic X-ray scattering to show evidence for magnetic polarons in magnetite and provide insight into the nature of the transition.
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Affiliation(s)
- H Y Huang
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan.,Program of Science and Technology of Synchrotron Light Source, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Z Y Chen
- Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - R-P Wang
- Inorganic Chemistry and Catalysis, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands
| | - F M F de Groot
- Inorganic Chemistry and Catalysis, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands
| | - W B Wu
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - J Okamoto
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - A Chainani
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - A Singh
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Z-Y Li
- Department of Mechanical Engineering, Texas Material Institute, University of Texas at Austin, Austin, Texas 78712, USA
| | - J-S Zhou
- Department of Mechanical Engineering, Texas Material Institute, University of Texas at Austin, Austin, Texas 78712, USA
| | - H-T Jeng
- Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - G Y Guo
- Department of Physics, National Taiwan University, Taipei 10617, Taiwan.,Division of Physics, National Center for Theoretical Sciences, Hsinchu 30013, Taiwan
| | - Je-Geun Park
- Department of Physics and Astronomy, Seoul National University, Seoul 08826, Korea.,Center for Correlated Electron Systems, Institute for Basic Science, Seoul 08826, Korea
| | - L H Tjeng
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzerstr. 40, 01187 Dresden, Germany
| | - C T Chen
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - D J Huang
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan.,Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan
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10
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Perversi G, Cumby J, Pachoud E, Wright JP, Attfield JP. The Verwey structure of a natural magnetite. Chem Commun (Camb) 2016; 52:4864-7. [PMID: 26908195 DOI: 10.1039/c5cc10495e] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A remarkably complex electronic order of Fe(2+)/Fe(3+) charges, Fe(2+) orbital states, and weakly metal-metal bonded Fe3 units known as trimerons, was recently discovered in stoichiometric magnetite (Fe3O4) below the 125 K Verwey transition. Here, the low temperature crystal structure of a natural magnetite from a mineral sample has been determined using the same microcrystal synchrotron X-ray diffraction method. Structure refinement demonstrates that the natural sample has the same complex electronic order as pure synthetic magnetite, with only minor reductions of orbital and trimeron distortions. Chemical analysis shows that the natural sample contains dopants such as Al, Si, Mg and Mn at comparable concentrations to extraterrestrial magnetites, for example, as reported in the Tagish Lake meteorite. Much extraterrestrial magnetite exists at temperatures below the Verwey transition and hence our study demonstrates that the low temperature phase of magnetite represents the most complex long-range electronic order known to occur naturally.
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Affiliation(s)
- G Perversi
- Centre for Science at Extreme Conditions (CSEC) and School of Chemistry, University of Edinburgh, Edinburgh EH9 3FD, UK.
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11
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Bernal-Villamil I, Gallego S. Electronic phase transitions in ultrathin magnetite films. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:293202. [PMID: 26153727 DOI: 10.1088/0953-8984/27/29/293202] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Magnetite (Fe3O4) shows singular electronic and magnetic properties, resulting from complex electron-electron and electron-phonon interactions that involve the interplay of charge, orbital and spin degrees of freedom. The Verwey transition is a manifestation of these interactions, with a puzzling connection between the low temperature charge ordered state and the dynamic charge fluctuations still present above the transition temperature. Here we explore how these rich physical phenomena are affected by thin film geometries, particularly focusing on the ultimate size limit defined by thicknesses below the minimum bulk unit cell. On one hand, we address the influence of extended defects, such as surfaces or antiphase domains, on the novel features exhibited by thin films. On the other, we try to isolate the effect of the reduced thickness on the electronic and magnetic properties. We will show that a distinct phase diagram and novel charge distributions emerge under reduced dimensions, while holding the local high magnetic moments. Altogether, thin film geometries offer unique possibilities to understand the complex interplay of short- and long-range orders in the Verwey transition. Furthermore, they arise as interesting candidates for the exploitation of the rich physics of magnetite in devices that demand nanoscale geometries, additionally offering novel functionalities based on their distinct properties with respect to the bulk form.
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Affiliation(s)
- I Bernal-Villamil
- Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, Cantoblanco, 28049 Madrid, Spain
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12
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13
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Zschornak M, Richter C, Nentwich M, Stöcker H, Gemming S, Meyer DC. Probing a crystal's short-range structure and local orbitals by Resonant X-ray Diffraction methods. CRYSTAL RESEARCH AND TECHNOLOGY 2014. [DOI: 10.1002/crat.201300430] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Matthias Zschornak
- TU Bergakademie Freiberg; Institut für Experimentelle Physik; Leipziger Str. 23 09596 Freiberg Germany
| | - Carsten Richter
- TU Bergakademie Freiberg; Institut für Experimentelle Physik; Leipziger Str. 23 09596 Freiberg Germany
| | - Melanie Nentwich
- TU Bergakademie Freiberg; Institut für Experimentelle Physik; Leipziger Str. 23 09596 Freiberg Germany
| | - Hartmut Stöcker
- TU Bergakademie Freiberg; Institut für Experimentelle Physik; Leipziger Str. 23 09596 Freiberg Germany
| | - Sibylle Gemming
- Helmholtz-Zentrum Dresden-Rossendorf; Institut für Ionenstrahlphysik und Materialforschung; Bautzner Landstraße 400 01328 Dresden Germany
| | - Dirk C. Meyer
- TU Bergakademie Freiberg; Institut für Experimentelle Physik; Leipziger Str. 23 09596 Freiberg Germany
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14
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Attfield JP. The Verwey Phase of Magnetite: A Long-Running Mystery in Ferrites. ACTA ACUST UNITED AC 2014. [DOI: 10.2497/jjspm.61.s43] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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15
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de Jong S, Kukreja R, Trabant C, Pontius N, Chang CF, Kachel T, Beye M, Sorgenfrei F, Back CH, Bräuer B, Schlotter WF, Turner JJ, Krupin O, Doehler M, Zhu D, Hossain MA, Scherz AO, Fausti D, Novelli F, Esposito M, Lee WS, Chuang YD, Lu DH, Moore RG, Yi M, Trigo M, Kirchmann P, Pathey L, Golden MS, Buchholz M, Metcalf P, Parmigiani F, Wurth W, Föhlisch A, Schüßler-Langeheine C, Dürr HA. Speed limit of the insulator-metal transition in magnetite. NATURE MATERIALS 2013; 12:882-6. [PMID: 23892787 DOI: 10.1038/nmat3718] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2012] [Accepted: 06/24/2013] [Indexed: 05/19/2023]
Abstract
As the oldest known magnetic material, magnetite (Fe3O4) has fascinated mankind for millennia. As the first oxide in which a relationship between electrical conductivity and fluctuating/localized electronic order was shown, magnetite represents a model system for understanding correlated oxides in general. Nevertheless, the exact mechanism of the insulator-metal, or Verwey, transition has long remained inaccessible. Recently, three-Fe-site lattice distortions called trimerons were identified as the characteristic building blocks of the low-temperature insulating electronically ordered phase. Here we investigate the Verwey transition with pump-probe X-ray diffraction and optical reflectivity techniques, and show how trimerons become mobile across the insulator-metal transition. We find this to be a two-step process. After an initial 300 fs destruction of individual trimerons, phase separation occurs on a 1.5±0.2 ps timescale to yield residual insulating and metallic regions. This work establishes the speed limit for switching in future oxide electronics.
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Affiliation(s)
- S de Jong
- 1] Stanford Institute for Energy and Materials Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA [2]
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16
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Hoesch M, Piekarz P, Bosak A, Le Tacon M, Krisch M, Kozłowski A, Oleś AM, Parlinski K. Anharmonicity due to electron-phonon coupling in magnetite. PHYSICAL REVIEW LETTERS 2013; 110:207204. [PMID: 25167445 DOI: 10.1103/physrevlett.110.207204] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2012] [Indexed: 05/22/2023]
Abstract
We present the results of inelastic x-ray scattering for magnetite and analyze the energies and widths of the phonon modes with different symmetries in a broad range of temperature 125 < T < 293 K. The phonon modes with X(4) and Δ(5) symmetries broaden in a nonlinear way with decreasing T when the Verwey transition is approached. It is found that the maxima of phonon widths occur away from high-symmetry points, which suggests the incommensurate character of critical fluctuations. Strong phonon anharmonicity induced by electron-phonon coupling is discovered by a combination of these experimental results with ab initio calculations which take into account local Coulomb interactions at Fe ions. It (i) explains observed anomalous phonon broadening and (ii) demonstrates that the Verwey transition is a cooperative phenomenon which involves a wide spectrum of phonons coupled to the electron charge fluctuations condensing in the low-symmetry phase.
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Affiliation(s)
- Moritz Hoesch
- Diamond Light Source, Harwell Campus, Didcot OX11 0DE, Oxfordshire, United Kingdom
| | - Przemysław Piekarz
- Institute of Nuclear Physics, Polish Academy of Sciences, Radzikowskiego 152, PL-31342 Kraków, Poland
| | - Alexey Bosak
- European Synchrotron Radiation Facility, 6 rue Jules Horowitz, F-38043 Grenoble Cedex, France
| | - Mathieu Le Tacon
- Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
| | - Michael Krisch
- European Synchrotron Radiation Facility, 6 rue Jules Horowitz, F-38043 Grenoble Cedex, France
| | - Andrzej Kozłowski
- Faculty of Physics and Applied Computer Science, AGH-University of Science and Technology, Aleja Mickiewicza 30, PL-30059 Kraków, Poland
| | - Andrzej M Oleś
- Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany and Marian Smoluchowski Institute of Physics, Jagellonian University, Reymonta 4, PL-30059 Kraków, Poland
| | - Krzysztof Parlinski
- Institute of Nuclear Physics, Polish Academy of Sciences, Radzikowskiego 152, PL-31342 Kraków, Poland
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Benjamin D, Abanin D, Abbamonte P, Demler E. Microscopic theory of resonant soft-x-ray scattering in materials with charge order: the example of charge stripes in high-temperature cuprate superconductors. PHYSICAL REVIEW LETTERS 2013; 110:137002. [PMID: 23581360 DOI: 10.1103/physrevlett.110.137002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2012] [Indexed: 06/02/2023]
Abstract
We present a microscopic theory of resonant soft-x-ray scattering that accounts for the delocalized character of valence electrons. Unlike past approaches based on local form factors, our functional determinant method treats realistic band structures. This method builds upon earlier theoretical work in mesoscopic physics and accounts for excitonic effects as well as the orthogonality catastrophe arising from interaction between the core hole and the valence band electrons. We show that the two-peak structure observed near the O K edge of stripe-ordered La1.875Ba0.125CuO4 is due to dynamical nesting within the canonical cuprate band structure. Our results provide evidence for reasonably well-defined, high-energy quasiparticles in cuprates and establish resonant soft-x-ray scattering as a bulk-sensitive probe of the electron quasiparticles.
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Affiliation(s)
- David Benjamin
- Physics Department, Harvard University, Cambridge, Massachusetts 02138, USA
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18
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Tabis W, Lorenzo JE, Kozlowski A, Kolodziej T, Tarnawski Z, Kakol Z, Mazzoli C, Walker HC, Jaouen N, Mannix D, Marin C, Honig JM. Effect of surface polishing and oxidization induced strain on electronic order at the Verwey transition in Fe3O4. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:055603. [PMID: 23300186 DOI: 10.1088/0953-8984/25/5/055603] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Following the controversy between two previous publications (Lorenzo et al 2008 Phys. Rev. Lett. 101 226401 and Garcia et al 2009 Phys. Rev. Lett. 102 176405), we report on the influence of mechanical polishing, and subsequent sample storage, on the electronic order at the Verwey transition of highly pure magnetite, Fe(3)O(4), by resonant x-ray scattering. Contrary to expectations, mechanically polishing the surface induces an inhomogeneous micron deep dead layer, probably of powdered Fe(3)O(4). In addition, we have found that polishing the sample immediately before the experiment influences and favors the appearance of long range order electronic correlations, whereas samples polished well in advance have their electronic order quenched. Conversely, lattice distortions associated with the Verwey transition appear less affected by the surface state. We conclude that mechanical polishing induces stresses at the surface that may propagate into the core of the single crystal sample. These strains relax with time, which affects the different order parameters, as measured by x-ray resonant diffraction.
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Affiliation(s)
- W Tabis
- AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, Al. A. Mickiewicza 30, 30-059 Krakow, Poland.
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19
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Ebad-Allah J, Baldassarre L, Sing M, Claessen R, Brabers VAM, Kuntscher CA. Polaron physics and crossover transition in magnetite probed by pressure-dependent infrared spectroscopy. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:035602. [PMID: 23221151 DOI: 10.1088/0953-8984/25/3/035602] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The optical properties of magnetite at room temperature were studied by infrared reflectivity measurements as a function of pressure up to 8 GPa. The optical conductivity spectrum consists of a Drude term, two sharp phonon modes, a far-infrared band at around 600 cm(-1) and a pronounced mid-infrared absorption band. With increasing pressure both absorption bands shift to lower frequencies and the phonon modes harden in a linear fashion. Based on the shape of the MIR band, the temperature dependence of the dc transport data, and the occurrence of the far-infrared band in the optical conductivity spectrum, the polaronic coupling strength in magnetite at room temperature should be classified as intermediate. For the lower energy phonon mode an abrupt increase of the linear pressure coefficient occurs at around 6 GPa, which could be attributed to minor alterations of the charge distribution among the different Fe sites.
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Affiliation(s)
- J Ebad-Allah
- Experimentalphysik 2, Universität Augsburg, D-86135 Augsburg, Germany
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20
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Kąkol Z, Owoc D, Przewoźnik J, Sikora M, Kapusta C, Zając D, Kozłowski A, Sabol J, Honig J. The effect of doping on global lattice properties of magnetite Fe3−xMexO4 (Me=Zn, Ti and Al). J SOLID STATE CHEM 2012. [DOI: 10.1016/j.jssc.2012.04.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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21
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Weng SC, Lee YR, Chen CG, Chu CH, Soo YL, Chang SL. Direct observation of charge ordering in magnetite using resonant multiwave x-ray diffraction. PHYSICAL REVIEW LETTERS 2012; 108:146404. [PMID: 22540813 DOI: 10.1103/physrevlett.108.146404] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2011] [Indexed: 05/12/2023]
Abstract
Charge disproportion at octahedral Fe sites in magnetite was observed at low temperature using two inversion-symmetry related three-wave resonant x-ray diffraction, 022-311 and 002-̅3̅1, near the iron K edge. Both of the three-wave cases involve the (002) forbidden-weak reflection. The self-normalized three-wave to two-wave (002) diffraction intensity ratio automatically cancels the self-absorption effect and leads to direct determination of charge disproportion for magnetite below 120 K. This approach provides a more direct and effective way for extracting charge-ordering information.
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Affiliation(s)
- Shih-Chang Weng
- Department of Physics, National Tsing Hua University, Hsinchu, Taiwan, ROC
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22
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Subías G, García J, Blasco J, Herrero-Martín J, Sánchez MC, Orna J, Morellón L. Structural distortion, charge modulation and local anisotropies in magnetite below the Verwey transition using resonant X-ray scattering. JOURNAL OF SYNCHROTRON RADIATION 2012; 19:159-173. [PMID: 22338674 DOI: 10.1107/s0909049512001367] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2011] [Accepted: 01/11/2012] [Indexed: 05/31/2023]
Abstract
The pattern of charge modulations and local anisotropies below the Verwey transition has been determined and quantified in high-quality Fe(3)O(4) single crystals and thin films grown on MgO by using resonant X-ray scattering at the Fe K-edge. The energy, polarization and azimuthal angle dependencies of an extensive set of reflections with potential sensitivity to charge or local anisotropy orderings have been analyzed to explore their origins. A charge disproportion on octahedral B sites of 0.20 ± 0.05 e(-) with [0 0 1] and [1 1 0] cubic periodicities has been confirmed, while no significant charge disproportion has been obtained with [0 0 1/2] cubic periodicity. Additional charge modulations in the monoclinic a-b plane are also present. In addition, the occurrence of new forbidden (1, 1, 0) and (0, 0, 2n + 1/2) cubic reflections that arise from the anisotropy of the local structure around different tetrahedral and octahedral Fe atoms is shown. This complex pattern of weak charge modulations and local anisotropies is fully compatible with the low-temperature crystal structure refined in the non-polar C2/c space group and disproves any bimodal charge disproportion of the octahedral Fe atoms.
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Affiliation(s)
- Gloria Subías
- Instituto de Ciencia de Materiales de Aragón, CSIC-Universidad de Zaragoza, Departamento de Física de Materia Condensada, Pedro Cerbuna 12, 50009 Zaragoza, Spain.
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23
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Charge order and three-site distortions in the Verwey structure of magnetite. Nature 2011; 481:173-6. [PMID: 22190035 DOI: 10.1038/nature10704] [Citation(s) in RCA: 175] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2011] [Accepted: 11/08/2011] [Indexed: 11/08/2022]
Abstract
The mineral magnetite (Fe(3)O(4)) undergoes a complex structural distortion and becomes electrically insulating at temperatures less than 125 kelvin. Verwey proposed in 1939 that this transition is driven by a charge ordering of Fe(2+) and Fe(3+) ions, but the ground state of the low-temperature phase has remained contentious because twinning of crystal domains hampers diffraction studies of the structure. Recent powder diffraction refinements and resonant X-ray studies have led to proposals of a variety of charge-ordered and bond-dimerized ground-state models. Here we report the full low-temperature superstructure of magnetite, determined by high-energy X-ray diffraction from an almost single-domain, 40-micrometre grain, and identify the emergent order. The acentric structure is described by a superposition of 168 atomic displacement waves (frozen phonon modes), all with amplitudes of less than 0.24 ångströms. Distortions of the FeO(6) octahedra show that Verwey's hypothesis is correct to a first approximation and that the charge and Fe(2+) orbital order are consistent with a recent prediction. However, anomalous shortening of some Fe-Fe distances suggests that the localized electrons are distributed over linear three-Fe-site units, which we call 'trimerons'. The charge order and three-site distortions induce substantial off-centre atomic displacements and couple the resulting large electrical polarization to the magnetization. Trimerons may be important quasiparticles in magnetite above the Verwey transition and in other transition metal oxides.
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24
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García J, Subías G, Cuartero V, Herrero-Martin J. On the correlation between the X-ray absorption chemical shift and the formal valence state in mixed-valence manganites. JOURNAL OF SYNCHROTRON RADIATION 2010; 17:386-392. [PMID: 20400838 DOI: 10.1107/s0909049510010277] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2009] [Accepted: 03/18/2010] [Indexed: 05/29/2023]
Abstract
Here the correlation between the chemical shift in X-ray absorption spectroscopy, the geometrical structure and the formal valence state of the Mn atom in mixed-valence manganites are discussed. It is shown that this empirical correlation can be reliably used to determine the formal valence of Mn, using either X-ray absorption spectroscopy or resonant X-ray scattering techniques. The difficulties in obtaining a reliable comparison between experimental XANES spectra and theoretical simulations on an absolute energy scale are revealed. It is concluded that the contributions from the electronic occupation and the local structure to the XANES spectra cannot be separated either experimentally or theoretically. In this way the geometrical and electronic structure of the Mn atom in mixed-valence manganites cannot be described as a bimodal distribution of the formal integer Mn(3+) and Mn(4+) valence states corresponding to the undoped references.
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Affiliation(s)
- Joaquín García
- Instituto de Ciencia de Materiales de Aragón, CSIC-Universidad de Zaragoza, Facultad de Ciencias, Pza S. Francisco s/n, Zaragoza, Spain.
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25
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26
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Bland SR, Detlefs B, Wilkins SB, Beale TAW, Mazzoli C, Joly Y, Hatton PD, Lorenzo JE, Brabers VAM. Full polarization analysis of resonant superlattice and forbidden x-ray reflections in magnetite. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:485601. [PMID: 21832526 DOI: 10.1088/0953-8984/21/48/485601] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Despite being one of the oldest known magnetic materials, and the classic mixed valence compound, thought to be charge ordered, the structure of magnetite below the Verwey transition is complex and the presence and role of charge order is still being debated. Here, we present resonant x-ray diffraction data at the iron K-edge on forbidden (0, 0, 2n+1)(C) and superlattice [Formula: see text] reflections. Full linear polarization analysis of the incident and scattered light was conducted in order to explore the origins of the reflections. Through simulation of the resonant spectra we have confirmed that a degree of charge ordering takes place, while the anisotropic tensor of susceptibility scattering is responsible for the superlattice reflections below the Verwey transition. We also report the surprising result of the conversion of a significant proportion of the scattered light from linear to nonlinear polarization.
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Affiliation(s)
- S R Bland
- Department of Physics, University of Durham, Durham DH1 3LE, UK
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27
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Joly Y, Bunău O, Lorenzo JE, Galéra RM, Grenier S, Thompson B. Self-consistency, spin-orbit and other advances in the FDMNES code to simulate XANES and RXD experiments. ACTA ACUST UNITED AC 2009. [DOI: 10.1088/1742-6596/190/1/012007] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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28
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Tabiś W, Kusz J, Kim-Ngan NTH, Tarnawski Z, Zontone F, Kąkol Z, Kozłowski A. Structural changes at the Verwey transition in Fe3O4. Radiat Phys Chem Oxf Engl 1993 2009. [DOI: 10.1016/j.radphyschem.2009.02.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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29
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Mulders AM, Lawrence SM, Staub U, Garcia-Fernandez M, Scagnoli V, Mazzoli C, Pomjakushina E, Conder K, Wang Y. Direct observation of charge order and an orbital glass state in multiferroic LuFe2O4. PHYSICAL REVIEW LETTERS 2009; 103:077602. [PMID: 19792687 DOI: 10.1103/physrevlett.103.077602] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2008] [Indexed: 05/28/2023]
Abstract
Geometrical frustration of the Fe ions in LuFe2O4 leads to intricate charge and magnetic order and a strong magnetoelectric coupling. Using resonant x-ray diffraction at the Fe K edge, the anomalous scattering factors of both Fe sites are deduced from the (h/3 k/3 l/2) reflections. The chemical shift between the two types of Fe ions equals 4.0(1) eV corresponding to full charge separation into Fe2+ and Fe3+. The polarization and azimuthal angle dependence of the superlattice reflections demonstrate the absence of differences in anisotropic scattering revealing random orientations of the Fe2+ orbitals characteristic of an orbital glass state.
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Affiliation(s)
- A M Mulders
- Department of Imaging and Applied Physics, Curtin University of Technology, Perth, WA 6845, Australia
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30
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Shchennikov VV, Ovsyannikov SV. Is the Verwey transition in Fe(3)O(4) magnetite driven by a Peierls distortion? JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:271001. [PMID: 21828481 DOI: 10.1088/0953-8984/21/27/271001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
In this viewpoint article we analyse recent crucial structural, optical and transport experiments on Fe(3)O(4) magnetite across the Verwey transition at T(V)∼120-125 K. We find that all the relevant experimental data are consistent with a model of a Peierls distortion in the cubic spinel lattice, and likewise, some of them evidence against the original and still distributed hypothesis of the long range charge ordering origin of the Verwey transition. An estimated Peierls transition temperature (T(P)) is comparable with T(V). The Peierls model provides new insight into the electronic properties of magnetite. Application of the Peierls model to some other systems is briefly discussed also.
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Affiliation(s)
- Vladimir V Shchennikov
- High Pressure Group, Institute of Metal Physics, Russian Academy of Sciences, Urals Division, GSP-170, 18 S Kovalevskaya Street, Yekaterinburg 620041, Russia
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31
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García J, Subías G, Herrero-Martín J, Blasco J, Cuartero V, Sánchez MC, Mazzoli C, Yakhou F. Reexamination of the temperature dependences of resonant reflections in highly stoichiometric magnetite. PHYSICAL REVIEW LETTERS 2009; 102:176405. [PMID: 19518805 DOI: 10.1103/physrevlett.102.176405] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2009] [Indexed: 05/27/2023]
Abstract
We have studied the temperature dependences of the so-called charge and orbital ordering reflections in the neighborhood of the Verwey transition by means of resonant x-ray scattering at the Fe K and L edges on a high purity single crystal of magnetite. Contrary to recently published results [J. E. Lorenzo, Phys. Rev. Lett. 101, 226401 (2008)10.1103/PhysRevLett.101.226401], we show that all the reflections studied disappear simultaneously at the Verwey transition for both edges, on and off resonance. This means that there is no correlation between the Verwey (123.5 K) and the spin-reorientation (130 K) transitions and that the resonant reflections are driven by the lattice distortions.
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Affiliation(s)
- Joaquín García
- Instituto de Ciencia de Materiales de Aragón, CSIC-Universidad de Zaragoza, Pedro Cerbuna 12, 50009 Zaragoza, Spain.
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32
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Lorenzo JE, Mazzoli C, Jaouen N, Detlefs C, Mannix D, Grenier S, Joly Y, Marin C. Charge and orbital correlations at and above the Verwey phase transition in magnetite. PHYSICAL REVIEW LETTERS 2008; 101:226401. [PMID: 19113492 DOI: 10.1103/physrevlett.101.226401] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2008] [Indexed: 05/27/2023]
Abstract
The subtle interplay among electronic degrees of freedom (charge and orbital orderings), spin and lattice distortion that conspire at the Verwey transition in magnetite (Fe3O4) is still a matter of controversy. Here, we provide compelling evidence that these electronic orderings are manifested as a continuous phase transition at the temperature where a spin reorientation takes place at around 130 K, i.e., well above TV approximately 121 K. The Verwey transition seems to leave the orbital ordering unaffected whereas the charge ordering development appears to be quenched at this temperature and the temperature dependence below TV is controlled by the lattice distortions. Finally, we show that the orbital ordering does not reach true long range (disorder), and the correlation length along the c-direction is limited to 100 angstroms.
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Affiliation(s)
- J E Lorenzo
- Institut Néel CNRS-UJF, BP 166X,F-38052 Grenoble Cedex 09, France
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33
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Lee S, Fursina A, Mayo JT, Yavuz CT, Colvin VL, Sofin RGS, Shvets IV, Natelson D. Electrically driven phase transition in magnetite nanostructures. NATURE MATERIALS 2008; 7:130-133. [PMID: 18084295 DOI: 10.1038/nmat2084] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2007] [Accepted: 11/16/2007] [Indexed: 05/25/2023]
Abstract
Magnetite (Fe3O4), an archetypal transition-metal oxide, has been used for thousands of years, from lodestones in primitive compasses to a candidate material for magnetoelectronic devices. In 1939, Verwey found that bulk magnetite undergoes a transition at TV approximately 120 K from a high-temperature 'bad metal' conducting phase to a low-temperature insulating phase. He suggested that high-temperature conduction is through the fluctuating and correlated valences of the octahedral iron atoms, and that the transition is the onset of charge ordering on cooling. The Verwey transition mechanism and the question of charge ordering remain highly controversial. Here, we show that magnetite nanocrystals and single-crystal thin films exhibit an electrically driven phase transition below the Verwey temperature. The signature of this transition is the onset of sharp conductance switching in high electric fields, hysteretic in voltage. We demonstrate that this transition is not due to local heating, but instead is due to the breakdown of the correlated insulating state when driven out of equilibrium by electrical bias. We anticipate that further studies of this newly observed transition and its low-temperature conducting phase will shed light on how charge ordering and vibrational degrees of freedom determine the ground state of this important compound.
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Affiliation(s)
- Sungbae Lee
- Department of Physics and Astronomy, Rice University, 6100 Main St., Houston, Texas 77005, USA
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34
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Schlappa J, Schüssler-Langeheine C, Chang CF, Ott H, Tanaka A, Hu Z, Haverkort MW, Schierle E, Weschke E, Kaindl G, Tjeng LH. Direct observation of t2g orbital ordering in magnetite. PHYSICAL REVIEW LETTERS 2008; 100:026406. [PMID: 18232896 DOI: 10.1103/physrevlett.100.026406] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2006] [Indexed: 05/12/2023]
Abstract
Using soft-x-ray diffraction at the site-specific resonances in the Fe L2,3 edge, we find clear evidence for orbital and charge ordering in magnetite below the Verwey transition. The spectra show directly that the (001/2) diffraction peak (in cubic notation) is caused by t2g orbital ordering at octahedral Fe2+ sites and the (001) by a spatial modulation of the t2g occupation.
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Affiliation(s)
- J Schlappa
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, D-50937 Köln, Germany
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35
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McQueeney RJ, Yethiraj M, Chang S, Montfrooij W, Perring TG, Honig JM, Metcalf P. Zener double exchange from local valence fluctuations in magnetite. PHYSICAL REVIEW LETTERS 2007; 99:246401. [PMID: 18233463 DOI: 10.1103/physrevlett.99.246401] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2007] [Indexed: 05/25/2023]
Abstract
Magnetite (Fe3O4) is a mixed valent system where electronic conductivity occurs on the B site (octahedral) iron sublattice of the spinel structure. Below T(V)=123 K, a metal-insulator transition occurs which is argued to arise from the charge ordering of 2+ and 3+ iron valences on the B sites (Verwey transition). Inelastic neutron scattering measurements show that optical spin waves propagating on the B site sublattice (approximately 80 meV) are shifted upwards in energy above T_{V} due to the occurrence of B-B ferromagnetic double exchange in the mixed valent phase. The double exchange interaction affects only spin waves of Delta(5) symmetry, not all modes, indicating that valence fluctuations are slow and the double exchange is constrained by short-range electron correlations above T(V).
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Affiliation(s)
- R J McQueeney
- Department of Physics & Astronomy, Iowa State University, Ames, Iowa 50011, USA
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Lodziana Z. Surface Verwey transition in magnetite. PHYSICAL REVIEW LETTERS 2007; 99:206402. [PMID: 18233166 DOI: 10.1103/physrevlett.99.206402] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2007] [Indexed: 05/25/2023]
Abstract
We report density functional studies of the (001) surface of magnetite that account for local Coulomb interactions. Iron cations in the surface layers exhibit charge and t2g orbital ordering that is coupled with the lattice strains. Orbital ordering is present for various surface stoichiometries and causes opening of the band gap Eg approximately 0.3 eV at the surface, such that the (001) surface of Fe3O4 remains insulating also in the high temperature cubic phase. The (radical 2 x radical 2)R45 degrees surface reconstruction is related to orbital ordering.
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Affiliation(s)
- Zbigniew Lodziana
- Institute of Nuclear Physics, Polish Academy of Sciences, ul. Radzikowskiego 152, PL-31-342 Kraków, Poland.
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Karen P, Gustafsson K, Lindén J. : Extent of charge ordering by Mössbauer spectroscopy and high-intensity high-resolution powder diffraction. J SOLID STATE CHEM 2007. [DOI: 10.1016/j.jssc.2006.09.021] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Pinto HP, Elliott SD. Mechanism of the Verwey transition in magnetite: Jahn-Teller distortion and charge ordering patterns. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2006; 18:10427-10436. [PMID: 21690927 DOI: 10.1088/0953-8984/18/46/010] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We have performed density functional calculations with on-site Coulomb repulsion corrections of systems that may be involved in the Verwey transition in magnetite (Fe(3)O(4)). We find that the lowest energy solution for the minority spin wavefunction in the cubic cell involves orbitally ordered Fe-d and O-p states, which breaks cubic symmetry. This leads to partial charge ordering that triggers a Jahn-Teller distortion and band-gap opening. Our results show this to be the essential mechanism of the Verwey transition. Applying ionic relaxation within a larger tetragonal cell, three patterns of charge ordering are compared and a Pmca pattern matching x-ray data is found to be the most stable.
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Affiliation(s)
- H P Pinto
- Tyndall National Institute, Lee Maltings, Cork, Republic of Ireland
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Piekarz P, Parlinski K, Oleś AM. Mechanism of the Verwey transition in magnetite. PHYSICAL REVIEW LETTERS 2006; 97:156402. [PMID: 17155347 DOI: 10.1103/physrevlett.97.156402] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2006] [Indexed: 05/12/2023]
Abstract
By combining ab initio results for the electronic structure and phonon spectrum with the group theory, we establish the origin of the Verwey transition in Fe3O4. Two primary order parameters with X3 and Delta5 symmetries are identified. They induce the phase transformation from the high-temperature cubic to the low-temperature monoclinic structure. The on-site Coulomb interaction U between 3d electrons at Fe ions plays a crucial role in this transition--it amplifies the coupling of phonons to conduction electrons and thus opens a gap at the Fermi energy.
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Affiliation(s)
- Przemysław Piekarz
- Institute of Nuclear Physics, Polish Academy of Sciences, Radzikowskiego 152, PL-31342 Kraków, Poland
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