1
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Guo H, Li ZW, Chang CF, Hu Z, Kuo CY, Perring TG, Schmidt W, Piovano A, Schmalzl K, Walker HC, Lin HJ, Chen CT, Blanco-Canosa S, Schlappa J, Schüßler-Langeheine C, Hansmann P, Khomskii DI, Tjeng LH, Komarek AC. Charge disproportionation and nano phase separation in [Formula: see text]. Sci Rep 2020; 10:18012. [PMID: 33093480 PMCID: PMC7582202 DOI: 10.1038/s41598-020-74884-2] [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] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Accepted: 09/04/2020] [Indexed: 11/29/2022] Open
Abstract
We have successfully grown centimeter-sized layered [Formula: see text] single crystals under high oxygen pressures of 120-150 bar by the floating zone technique. This enabled us to perform neutron scattering experiments where we observe close to quarter-integer magnetic peaks below [Formula: see text] that are accompanied by steep upwards dispersing spin excitations. Within the high-frequency Ni-O bond stretching phonon dispersion, a softening at the propagation vector for a checkerboard modulation can be observed. We were able to simulate the magnetic excitation spectra using a model that includes two essential ingredients, namely checkerboard charge disproportionation and nano phase separation. The results thus suggest that charge disproportionation is preferred instead of a Jahn-Teller distortion even for this layered [Formula: see text] system.
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Affiliation(s)
- H. Guo
- Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany
| | - Z. W. Li
- Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany
- Institute of Applied Magnetics, Key Lab for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou, 730000 People’s Republic of China
| | - C. F. Chang
- Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany
| | - Z. Hu
- Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany
| | - C.-Y. Kuo
- Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany
- National Synchrotron Radiation Research Center (NSRRC), 101 Hsin-Ann Road, Hsinchu, 30076 Taiwan
| | - T. G. Perring
- ISIS Facility, STFC Rutherford Appleton Laboratory, Harwell Oxford, Didcot, OX11 0QX UK
| | - W. Schmidt
- Forschungszentrum Jülich GmbH, Jülich Centre for Neutron Science at ILL, 71 avenue des Martyrs, 38000 Grenoble, France
| | - A. Piovano
- Institut Laue-Langevin, 71 avenue des Martyrs, 38000 Grenoble, France
| | - K. Schmalzl
- Forschungszentrum Jülich GmbH, Jülich Centre for Neutron Science at ILL, 71 avenue des Martyrs, 38000 Grenoble, France
| | - H. C. Walker
- ISIS Facility, STFC Rutherford Appleton Laboratory, Harwell Oxford, Didcot, OX11 0QX UK
| | - H. J. Lin
- National Synchrotron Radiation Research Center (NSRRC), 101 Hsin-Ann Road, Hsinchu, 30076 Taiwan
| | - C. T. Chen
- National Synchrotron Radiation Research Center (NSRRC), 101 Hsin-Ann Road, Hsinchu, 30076 Taiwan
| | - S. Blanco-Canosa
- IKERBASQUE, Basque Foundation for Science, 48013 Bilbao, Basque Country Spain
- Donostia International Physics Center, DIPC, 20018 Donostia-San Sebastian, Basque Country, Spain
| | - J. Schlappa
- European X-ray Free Electron Laser Facility GmbH, Holzkoppel 4, 22869 Schenefeld, Germany
| | - C. Schüßler-Langeheine
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Str. 15, 12489 Berlin, Germany
| | - P. Hansmann
- Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany
| | - D. I. Khomskii
- Physics Institute II, University of Cologne, Zülpicher Str. 77, 50937 Cologne, Germany
| | - L. H. Tjeng
- Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany
| | - A. C. Komarek
- Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany
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2
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Zhou J, Zhang L, Huang YC, Dong CL, Lin HJ, Chen CT, Tjeng LH, Hu Z. Voltage- and time-dependent valence state transition in cobalt oxide catalysts during the oxygen evolution reaction. Nat Commun 2020; 11:1984. [PMID: 32332788 PMCID: PMC7181785 DOI: 10.1038/s41467-020-15925-2] [Citation(s) in RCA: 58] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Accepted: 04/01/2020] [Indexed: 12/31/2022] Open
Abstract
The ability to determine the electronic structure of catalysts during electrochemical reactions is highly important for identification of the active sites and the reaction mechanism. Here we successfully applied soft X-ray spectroscopy to follow in operando the valence and spin state of the Co ions in Li2Co2O4 under oxygen evolution reaction (OER) conditions. We have observed that a substantial fraction of the Co ions undergo a voltage-dependent and time-dependent valence state transition from Co3+ to Co4+ accompanied by spontaneous delithiation, whereas the edge-shared Co-O network and spin state of the Co ions remain unchanged. Density functional theory calculations indicate that the highly oxidized Co4+ site, rather than the Co3+ site or the oxygen vacancy site, is mainly responsible for the high OER activity.
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Affiliation(s)
- Jing Zhou
- Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201800, China
| | - Linjuan Zhang
- Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201800, China. .,University of Chinese Academy of Sciences, Beijing, 100049, China.
| | - Yu-Cheng Huang
- Department of Physics, Tamkang University, 151 Yingzhuan Road, New Taipei City, 25137, Taiwan
| | - Chung-Li Dong
- Department of Physics, Tamkang University, 151 Yingzhuan Road, New Taipei City, 25137, Taiwan
| | - Hong-Ji Lin
- National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu, 30076, Taiwan
| | - Chien-Te Chen
- National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu, 30076, Taiwan
| | - L H Tjeng
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, 01187, Dresden, Germany
| | - Zhiwei Hu
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, 01187, Dresden, Germany.
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3
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Liu XH, Chang CF, Tjeng LH, Komarek AC, Wirth S. Large magnetoresistance effects in Fe 3O 4. J Phys Condens Matter 2019; 31:225803. [PMID: 30836348 DOI: 10.1088/1361-648x/ab0cf4] [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] [Indexed: 06/09/2023]
Abstract
We investigated the magnetoresistance (MR) of a single crystal of magnetite, Fe3O4. In an effort to distinguish between different contributions to the MR the samples were prepared in two different initial magnetic states, i.e. by either zero-field or by field cooling from room temperature. The different magnetic structures in this sample have a dramatic effect on the magnetoresistance: for initially zero-field-cooled conditions a negative MR of about -20% is observed just below the Verwey transition at [Formula: see text] K. For decreasing temperature the MR increases, changes sign at ∼78 K and reaches a record positive value of ∼45% at around 50 K. This behavior is completely absent in the field-cooled sample. Magnetization measurements corroborate an alignment of the easy magnetization direction in applied magnetic fields below [Formula: see text] as a cause of the strong effects observed in both, magnetization and MR. Our results point to a complex interplay of structural and magnetocrystalline effects taking place upon cooling Fe3O4 through [Formula: see text].
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Affiliation(s)
- X H Liu
- Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany. State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, People's Republic of China
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4
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Sundermann M, Yavaş H, Chen K, Kim DJ, Fisk Z, Kasinathan D, Haverkort MW, Thalmeier P, Severing A, Tjeng LH. 4f Crystal Field Ground State of the Strongly Correlated Topological Insulator SmB_{6}. Phys Rev Lett 2018; 120:016402. [PMID: 29350947 DOI: 10.1103/physrevlett.120.016402] [Citation(s) in RCA: 6] [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: 06/20/2017] [Revised: 09/25/2017] [Indexed: 06/07/2023]
Abstract
We investigated the crystal-electric field ground state of the 4f manifold in the strongly correlated topological insulator SmB_{6} using core-level nonresonant inelastic x-ray scattering. The directional dependence of the scattering function that arises from higher multipole transitions establishes unambiguously that the Γ_{8} quartet state of the Sm f^{5} J=5/2 configuration governs the ground-state symmetry and, hence, the topological properties of SmB_{6}. Our findings contradict the results of density functional calculations reported so far.
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Affiliation(s)
- M Sundermann
- Institute of Physics II, University of Cologne, Zülpicher Straße 77, 50937 Cologne, Germany
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - H Yavaş
- PETRA III, Deutsches Elektronen-Synchrotron (DESY), Notkestraße 85, 22607 Hamburg, Germany
| | - K Chen
- Institute of Physics II, University of Cologne, Zülpicher Straße 77, 50937 Cologne, Germany
| | - D J Kim
- Department of Physics and Astronomy, University of California, Irvine, California 92697, USA
| | - Z Fisk
- Department of Physics and Astronomy, University of California, Irvine, California 92697, USA
| | - D Kasinathan
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - M W Haverkort
- Institute for Theoretical Physics, Heidelberg University, Philosophenweg 19, 69120 Heidelberg, Germany
| | - P Thalmeier
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - A Severing
- Institute of Physics II, University of Cologne, Zülpicher Straße 77, 50937 Cologne, Germany
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - L H Tjeng
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
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5
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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6
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Jiao L, Rößler S, Kim DJ, Tjeng LH, Fisk Z, Steglich F, Wirth S. Additional energy scale in SmB 6 at low-temperature. Nat Commun 2016; 7:13762. [PMID: 27941948 PMCID: PMC5159841 DOI: 10.1038/ncomms13762] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Accepted: 10/31/2016] [Indexed: 11/09/2022] Open
Abstract
Topological insulators give rise to exquisite electronic properties because of their spin-momentum locked Dirac-cone-like band structure. Recently, it has been suggested that the required opposite parities between valence and conduction band along with strong spin-orbit coupling can be realized in correlated materials. Particularly, SmB6 has been proposed as candidate material for a topological Kondo insulator. Here we observe, by utilizing scanning tunnelling microscopy and spectroscopy down to 0.35 K, several states within the hybridization gap of about ±20 meV on well characterized (001) surfaces of SmB6. The spectroscopic response to impurities and magnetic fields allows to distinguish between dominating bulk and surface contributions to these states. The surface contributions develop particularly strongly below about 7 K, which can be understood in terms of a suppressed Kondo effect at the surface. Our high-resolution data provide insight into the electronic structure of SmB6, which reconciles many current discrepancies on this compound.
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Affiliation(s)
- L. Jiao
- Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany
| | - S. Rößler
- Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany
| | - D. J. Kim
- Department of Physics and Astronomy, University of California, Irvine, CA 92697, USA
| | - L. H. Tjeng
- Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany
| | - Z. Fisk
- Department of Physics and Astronomy, University of California, Irvine, CA 92697, USA
| | - F. Steglich
- Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany
- Center for Correlated Matter, Zhejiang University, Hangzhou 310058, China
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - S. Wirth
- Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany
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7
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Zhao Q, Liu M, Dai J, Deng H, Yin Y, Zhou L, Yang J, Hu Z, Agrestini S, Chen K, Pellegrin E, Valvidares M, Nataf L, Baudelet F, Tjeng LH, Yang YF, Jin C, Long Y. High-Pressure Synthesis and Ferrimagnetic Ordering of the B-Site-Ordered Cubic Perovskite Pb2FeOsO6. Inorg Chem 2016; 55:9816-9821. [DOI: 10.1021/acs.inorgchem.6b01649] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Qing Zhao
- Beijing
National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Min Liu
- Beijing
National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Jianhong Dai
- Beijing
National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Hongshan Deng
- Beijing
National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Yunyu Yin
- Beijing
National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Long Zhou
- Beijing
National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Junye Yang
- Beijing
National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Zhiwei Hu
- Max-Planck Institute for Chemical Physics of Solids, Nothnitzer Straße 40, 01187 Dresden, Germany
| | - Stefano Agrestini
- Max-Planck Institute for Chemical Physics of Solids, Nothnitzer Straße 40, 01187 Dresden, Germany
| | - Kai Chen
- Institute of Physics II, University of Cologne, Zulpicher
Straße 77, 50937 Cologne, Germany
| | - Eric Pellegrin
- ALBA Synchrotron Light Source, E-08290 Cerdanyola del Valles, Barcelona, Spain
| | - Manuel Valvidares
- ALBA Synchrotron Light Source, E-08290 Cerdanyola del Valles, Barcelona, Spain
| | - Lucie Nataf
- Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette Cedex, France
| | - François Baudelet
- Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette Cedex, France
| | - L. H. Tjeng
- Max-Planck Institute for Chemical Physics of Solids, Nothnitzer Straße 40, 01187 Dresden, Germany
| | - Yi-feng Yang
- Beijing
National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100190, China
| | - Changqing Jin
- Beijing
National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100190, China
| | - Youwen Long
- Beijing
National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100190, China
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8
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Jiang WB, Yang L, Guo CY, Hu Z, Lee JM, Smidman M, Wang YF, Shang T, Cheng ZW, Gao F, Ishii H, Tsuei KD, Liao YF, Lu X, Tjeng LH, Chen JM, Yuan HQ. Crossover from a heavy fermion to intermediate valence state in noncentrosymmetric Yb2Ni12(P,As)7. Sci Rep 2015; 5:17608. [PMID: 26626431 PMCID: PMC4667268 DOI: 10.1038/srep17608] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Accepted: 11/03/2015] [Indexed: 11/16/2022] Open
Abstract
We report measurements of the physical properties and electronic structure of the hexagonal compounds Yb2Ni12Pn7 (Pn = P, As) by measuring the electrical resistivity, magnetization, specific heat and partial fluorescence yield x-ray absorption spectroscopy (PFY-XAS). These demonstrate a crossover upon reducing the unit cell volume, from an intermediate valence state in Yb2Ni12As7 to a heavy-fermion paramagnetic state in Yb2Ni12P7, where the Yb is nearly trivalent. Application of pressure to Yb2Ni12P7 suppresses TFL, the temperature below which Fermi liquid behavior is recovered, suggesting the presence of a quantum critical point (QCP) under pressure. However, while there is little change in the Yb valence of Yb2Ni12P7 up to 30 GPa, there is a strong increase for Yb2Ni12As7 under pressure, before a near constant value is reached. These results indicate that any magnetic QCP in this system is well separated from strong valence fluctuations. The pressure dependence of the valence and lattice parameters of Yb2Ni12As7 are compared and at 1 GPa, there is an anomaly in the unit cell volume as well as a change in the slope of the Yb valence, indicating a correlation between structural and electronic changes.
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Affiliation(s)
- W B Jiang
- Center for Correlated Matter and Department of Physics, Zhejiang University, Hangzhou, 310058, China
| | - L Yang
- Center for Correlated Matter and Department of Physics, Zhejiang University, Hangzhou, 310058, China
| | - C Y Guo
- Center for Correlated Matter and Department of Physics, Zhejiang University, Hangzhou, 310058, China
| | - Z Hu
- Max Planck Institute for Chemical Physics of Solids, D-01187 Dresden, Germany
| | - J M Lee
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - M Smidman
- Center for Correlated Matter and Department of Physics, Zhejiang University, Hangzhou, 310058, China
| | - Y F Wang
- Center for Correlated Matter and Department of Physics, Zhejiang University, Hangzhou, 310058, China
| | - T Shang
- Center for Correlated Matter and Department of Physics, Zhejiang University, Hangzhou, 310058, China
| | - Z W Cheng
- Center for Correlated Matter and Department of Physics, Zhejiang University, Hangzhou, 310058, China
| | - F Gao
- Center for Correlated Matter and Department of Physics, Zhejiang University, Hangzhou, 310058, China
| | - H Ishii
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - K D Tsuei
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Y F Liao
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - X Lu
- Center for Correlated Matter and Department of Physics, Zhejiang University, Hangzhou, 310058, China.,Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China
| | - L H Tjeng
- Max Planck Institute for Chemical Physics of Solids, D-01187 Dresden, Germany
| | - J M Chen
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - H Q Yuan
- Center for Correlated Matter and Department of Physics, Zhejiang University, Hangzhou, 310058, China.,Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China
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9
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Istomin SY, Tyablikov OA, Kazakov SM, Antipov EV, Kurbakov AI, Tsirlin AA, Hollmann N, Chin YY, Lin HJ, Chen CT, Tanaka A, Tjeng LH, Hu Z. An unusual high-spin ground state of Co3+ in octahedral coordination in brownmillerite-type cobalt oxide. Dalton Trans 2015; 44:10708-13. [DOI: 10.1039/c4dt03670k] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
High-spin ground state of Co3+ was found in brownmillerite-like Sr2Co1.2Ga0.8O5 by low-temperature NPD and XAS study.
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10
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Kuo CY, Drees Y, Fernández-Díaz MT, Zhao L, Vasylechko L, Sheptyakov D, Bell AMT, Pi TW, Lin HJ, Wu MK, Pellegrin E, Valvidares SM, Li ZW, Adler P, Todorova A, Küchler R, Steppke A, Tjeng LH, Hu Z, Komarek AC. k=0 magnetic structure and absence of ferroelectricity in SmFeO3. Phys Rev Lett 2014; 113:217203. [PMID: 25479519 DOI: 10.1103/physrevlett.113.217203] [Citation(s) in RCA: 10] [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: 06/18/2014] [Indexed: 06/04/2023]
Abstract
SmFeO3 has attracted considerable attention very recently due to its reported multiferroic properties above room temperature. We have performed powder and single crystal neutron diffraction as well as complementary polarization dependent soft X-ray absorption spectroscopy measurements on floating-zone grown SmFeO3 single crystals in order to determine its magnetic structure. We found a k=0 G-type collinear antiferromagnetic structure that is not compatible with inverse Dzyaloshinskii-Moriya interaction driven ferroelectricity. While the structural data reveal a clear sign for magneto-elastic coupling at the Néel-temperature of ∼675 K, the dielectric measurements remain silent as far as ferroelectricity is concerned.
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Affiliation(s)
- C-Y Kuo
- Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, 01187 Dresden, Germany
| | - Y Drees
- Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, 01187 Dresden, Germany
| | | | - L Zhao
- Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
| | - L Vasylechko
- Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, 01187 Dresden, Germany and Lviv Polytechnic National University, 12 Bandera Street, 79013 Lviv, Ukraine
| | - D Sheptyakov
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - A M T Bell
- HASYLAB at DESY, Notkestrasse 85, 22607 Hamburg, Germany
| | - T W Pi
- National Synchrotron Radiation Research Center (NSRRC), 101 Hsin-Ann Road, Hsinchu 30077, Taiwan
| | - H-J Lin
- National Synchrotron Radiation Research Center (NSRRC), 101 Hsin-Ann Road, Hsinchu 30077, Taiwan
| | - M-K Wu
- Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
| | - E Pellegrin
- CELLS-ALBA Synchrotron Radiation Facility, Carretera BP 1413, km 3.3, E-08290 Cerdanyola del Vallès, Barcelona, Spain
| | - S M Valvidares
- CELLS-ALBA Synchrotron Radiation Facility, Carretera BP 1413, km 3.3, E-08290 Cerdanyola del Vallès, Barcelona, Spain
| | - Z W Li
- Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, 01187 Dresden, Germany
| | - P Adler
- Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, 01187 Dresden, Germany
| | - A Todorova
- Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, 01187 Dresden, Germany
| | - R Küchler
- Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, 01187 Dresden, Germany
| | - A Steppke
- Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, 01187 Dresden, Germany
| | - L H Tjeng
- Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, 01187 Dresden, Germany
| | - Z Hu
- Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, 01187 Dresden, Germany
| | - A C Komarek
- Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, 01187 Dresden, Germany
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11
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Khuntia P, Peratheepan P, Strydom AM, Utsumi Y, Ko KT, Tsuei KD, Tjeng LH, Steglich F, Baenitz M. Contiguous 3d and 4f magnetism: strongly correlated 3d electrons in YbFe2Al10. Phys Rev Lett 2014; 113:216403. [PMID: 25479509 DOI: 10.1103/physrevlett.113.216403] [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: 02/19/2014] [Indexed: 06/04/2023]
Abstract
We present magnetization, specific heat, and (27)Al NMR investigations on YbFe2Al10 over a wide range in temperature and magnetic field. The magnetic susceptibility at low temperatures is strongly enhanced at weak magnetic fields, accompanied by a ln(T0/T) divergence of the low-T specific heat coefficient in zero field, which indicates a ground state of correlated electrons. From our hard-x-ray photoemission spectroscopy study, the Yb valence at 50 K is evaluated to be 2.38. The system displays valence fluctuating behavior in the low to intermediate temperature range, whereas above 400 K, Yb(3+) carries a full and stable moment, and Fe carries a moment of about 3.1 μB. The enhanced value of the Sommerfeld-Wilson ratio and the dynamic scaling of the spin-lattice relaxation rate divided by T[(27)(1/T1T)] with static susceptibility suggests admixed ferromagnetic correlations. (27)(1/T1T) simultaneously tracks the valence fluctuations from the 4f Yb ions in the high temperature range and field dependent antiferromagnetic correlations among partially Kondo screened Fe 3d moments at low temperature; the latter evolve out of an Yb 4f admixed conduction band.
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Affiliation(s)
- P Khuntia
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
| | - P Peratheepan
- Highly Correlated Matter Research Group, Physics Department, University of Johannesburg, P.O. Box 524, Auckland Park 2006, South Africa and Department of Physics, Eastern University, Vantharumoolai, Chenkalady 30350, Sri Lanka
| | - A M Strydom
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany and Highly Correlated Matter Research Group, Physics Department, University of Johannesburg, P.O. Box 524, Auckland Park 2006, South Africa
| | - Y Utsumi
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
| | - K-T Ko
- Max Planck POSTECH Center for Complex Phase Materials, 01187 Dresden, Germany and Pohang 790-784, Korea
| | - K-D Tsuei
- National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu 30077, Taiwan
| | - L H Tjeng
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
| | - F Steglich
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
| | - M Baenitz
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
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12
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Yang JC, He Q, Suresha SJ, Kuo CY, Peng CY, Haislmaier RC, Motyka MA, Sheng G, Adamo C, Lin HJ, Hu Z, Chang L, Tjeng LH, Arenholz E, Podraza NJ, Bernhagen M, Uecker R, Schlom DG, Gopalan V, Chen LQ, Chen CT, Ramesh R, Chu YH. Orthorhombic BiFeO3. Phys Rev Lett 2012; 109:247606. [PMID: 23368382 DOI: 10.1103/physrevlett.109.247606] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2012] [Revised: 09/07/2012] [Indexed: 05/12/2023]
Abstract
A new orthorhombic phase of the multiferroic BiFeO3 has been created via strain engineering by growing it on a NdScO(3)(110)(o) substrate. The tensile-strained orthorhombic BiFeO3 phase is ferroelectric and antiferromagnetic at room temperature. A combination of nonlinear optical second harmonic generation and piezoresponse force microscopy revealed that the ferroelectric polarization in the orthorhombic phase is along the in-plane {110}(pc) directions. In addition, the corresponding rotation of the antiferromagnetic axis in this new phase was observed using x-ray linear dichroism.
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Affiliation(s)
- J C Yang
- Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 300, Taiwan
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13
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Willers T, Strigari F, Hiraoka N, Cai YQ, Haverkort MW, Tsuei KD, Liao YF, Seiro S, Geibel C, Steglich F, Tjeng LH, Severing A. Determining the in-plane orientation of the ground-state orbital of CeCu2Si2. Phys Rev Lett 2012; 109:046401. [PMID: 23006099 DOI: 10.1103/physrevlett.109.046401] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2012] [Indexed: 06/01/2023]
Abstract
We have successfully determined the hitherto unknown sign of the B(4)(4) Stevens crystal-field parameter of the tetragonal heavy-fermion compound CeCu(2)Si(2) using vector q-dependent nonresonant inelastic x-ray scattering experiments at the cerium N(4,5) edge. The observed difference between the two different directions, q∥[100] and q∥[110], is due to the anisotropy of the crystal-field ground state in the (001) plane and is observable only because of the utilization of higher than dipole transitions possible in nonresonant inelastic x-ray scattering. This approach allows us to go beyond the specific limitations of dc magnetic susceptibility, inelastic neutron scattering, and soft x-ray spectroscopy, and provides us with a reliable information about the orbital state of the 4f electrons relevant for the quantitative modeling of the quasiparticles and their interactions in heavy-fermion systems.
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Affiliation(s)
- T Willers
- Institute of Physics II, University of Cologne, Zülpicher Straße 77, D-50937 Cologne, Germany
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14
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Tanaka A, Chang CF, Buchholz M, Trabant C, Schierle E, Schlappa J, Schmitz D, Ott H, Metcalf P, Tjeng LH, Schüßler-Langeheine C. Symmetry of orbital order in Fe3O4 studied by Fe L(2,3) resonant x-ray diffraction. Phys Rev Lett 2012; 108:227203. [PMID: 23003646 DOI: 10.1103/physrevlett.108.227203] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2011] [Indexed: 06/01/2023]
Abstract
We studied the symmetry of the Fe 3d wave function in magnetite below the Verwey temperature T(V) with resonant soft-x-ray diffraction. Although the lattice structure of the low-temperature phase of Fe(3)O(4) is well described by the pseudo-orthorhombic Pmca with a slight monoclinic P2/c distortion, we find that the 3d wave function does not reflect the Pmca symmetry, and its distortion toward monoclinic symmetry is by far larger than that of the lattice. The result supports a scenario in which the Verwey transition involves the ordering of t(2g) orbitals with complex-number coefficients.
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Affiliation(s)
- A Tanaka
- Department of Quantum Matters, ADSM, Hiroshima University, Higashi-Hiroshima 739-8530, Japan
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15
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Ackerbauer SV, Senyshyn A, Borrmann H, Burkhardt U, Ormeci A, Rosner H, Schnelle W, Gamża M, Gumeniuk R, Ramlau R, Bischoff E, Schuster JC, Weitzer F, Leithe-Jasper A, Tjeng LH, Grin Y. Structural Transformation with “Negative Volume Expansion”: Chemical Bonding and Physical Behavior of TiGePt. Chemistry 2012; 18:6272-83. [PMID: 22461109 DOI: 10.1002/chem.201102401] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2011] [Revised: 01/25/2012] [Indexed: 11/07/2022]
Affiliation(s)
- S-V Ackerbauer
- Max-Planck-Institut für Chemische Physik fester Stoffe, Nöthnitzer Straße 40, 01187 Dresden, Germany
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16
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Schlappa J, Chang CF, Hu Z, Schierle E, Ott H, Weschke E, Kaindl G, Huijben M, Rijnders G, Blank DHA, Tjeng LH, Schüssler-Langeheine C. Resonant soft x-ray scattering from stepped surfaces of SrTiO3. J Phys Condens Matter 2012; 24:035501. [PMID: 22179392 DOI: 10.1088/0953-8984/24/3/035501] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We studied the resonant diffraction signal from stepped surfaces of SrTiO(3) at the Ti 2p → 3d (L(2,3)) resonance in comparison with x-ray absorption (XAS) and specular reflectivity data. The steps on the surface form an artificial superstructure suitable as a model system for resonant soft x-ray diffraction. A small step density on the surface is sufficient to produce a well defined diffraction peak. We determined the optical parameters of the sample across the resonance and found that the differences between the energy dependence of the x-ray absorption signal, the specular reflectivity and the step-related peak reflect the different quantities probed in these signals. When recorded at low incidence or detection angles, XAS and specular reflectivity spectra are strongly distorted by the changes of the angle of total reflection with energy. The resonant diffraction spectrum is less affected and can be used as a spectroscopic probe even in less favorable geometries.
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Affiliation(s)
- J Schlappa
- II. Physikalisches Institut, Universität zu Köln, Köln, Germany.
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17
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Willers T, Cezar JC, Brookes NB, Hu Z, Strigari F, Körner P, Hollmann N, Schmitz D, Bianchi A, Fisk Z, Tanaka A, Tjeng LH, Severing A. Magnetic field induced orbital polarization in cubic YbInNi4: determining the quartet ground state using x-ray linear dichroism. Phys Rev Lett 2011; 107:236402. [PMID: 22182107 DOI: 10.1103/physrevlett.107.236402] [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: 03/08/2011] [Revised: 09/29/2011] [Indexed: 05/31/2023]
Abstract
We have been able to induce a linear dichroic signal in the Yb M(5) x-ray absorption white line of cubic YbInNi(4) by the application of a magnetic field. The nonzero integrated intensity of the magnetic field induced dichroic spectrum indicates a net noncubic 4f orbital polarization. A quantitative analysis of the temperature and field strength dependence establishes that the crystal-field ground state is a Γ(8) quartet. The results demonstrate the potential of magnetic field induced linear dichroism as a new powerful approach for the investigation of the degeneracy and orbital degrees of freedom of cubic heavy-fermion and Kondo systems.
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Affiliation(s)
- T Willers
- Institute of Physics II, University of Cologne, Zülpicher Strasse 77, D-50937 Cologne, Germany
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18
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Zhang JX, He Q, Trassin M, Luo W, Yi D, Rossell MD, Yu P, You L, Wang CH, Kuo CY, Heron JT, Hu Z, Zeches RJ, Lin HJ, Tanaka A, Chen CT, Tjeng LH, Chu YH, Ramesh R. Microscopic origin of the giant ferroelectric polarization in tetragonal-like BiFeO(3). Phys Rev Lett 2011; 107:147602. [PMID: 22107234 DOI: 10.1103/physrevlett.107.147602] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2011] [Indexed: 05/12/2023]
Abstract
We report direct experimental evidence for a room-temperature, ∼130 μC/cm(2) ferroelectric polarization from the tetragonal-like BiFeO(3) phase. The physical origin of this remarkable enhancement of ferroelectric polarization has been investigated by a combination of x-ray absorption spectroscopy, scanning transmission electron microscopy, and first principles calculations. A large strain-induced Fe-ion displacement relative to the oxygen octahedra, combined with the contribution of Bi 6s lone pair electrons, is the mechanism driving the large ferroelectric polarization in this tetragonal-like phase.
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Affiliation(s)
- J X Zhang
- Department of Physics, University of California, Berkeley, California 94720, USA.
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19
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Chakhalian J, Rondinelli JM, Liu J, Gray BA, Kareev M, Moon EJ, Prasai N, Cohn JL, Varela M, Tung IC, Bedzyk MJ, Altendorf SG, Strigari F, Dabrowski B, Tjeng LH, Ryan PJ, Freeland JW. Asymmetric orbital-lattice interactions in ultrathin correlated oxide films. Phys Rev Lett 2011; 107:116805. [PMID: 22026694 DOI: 10.1103/physrevlett.107.116805] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2011] [Indexed: 05/23/2023]
Abstract
Using resonant x-ray spectroscopies combined with density functional calculations, we find an asymmetric biaxial strain-induced d-orbital response in ultrathin films of the correlated metal LaNiO3 which are not accessible in the bulk. The sign of the misfit strain governs the stability of an octahedral "breathing" distortion, which, in turn, produces an emergent charge-ordered ground state with an altered ligand-hole density and bond covalency. Control of this new mechanism opens a pathway to rational orbital engineering, providing a platform for artificially designed Mott materials.
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Affiliation(s)
- J Chakhalian
- Department of Physics, University of Arkansas, Fayetteville, Arkansas 70701, USA.
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20
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Ohta H, Yoshimura K, Hu Z, Chin YY, Lin HJ, Hsieh HH, Chen CT, Tjeng LH. Determination of the Co valence in bilayer hydrated superconducting NaxCoO2 · yH2O by soft x-ray absorption spectroscopy. Phys Rev Lett 2011; 107:066404. [PMID: 21902348 DOI: 10.1103/physrevlett.107.066404] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2010] [Indexed: 05/31/2023]
Abstract
We addressed the so-far unresolved issue concerning the Co valence in the superconducting bilayer hydrated Na(x)CoO(2) · yH(2)O (x∼0.35, y∼1.3) using soft x-ray absorption spectroscopy at the Co-L(2,3) and O-K edges. We find that the valence state of the Co lies in a narrow range from +3.3 to +3.4 for all studied Na(x)CoO(2) · yH(2)O samples and their deuterated analogue with T(c)'s ranging from 3.8 to 4.7 K. These valence values are far from the often claimed +3.7, the number based on the Na content only. We propose to modify the phase diagram accordingly, where the basic electronic structure of the superconducting phase is very close to that of the Na(0.7)CoO(2) system, suggesting that the presence of in-plane spin fluctuations could play an important role for the superconductivity.
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Affiliation(s)
- H Ohta
- Department of Chemistry, Graduate School of Science, Kyoto University, Japan.
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21
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Chang CF, Hu Z, Wu H, Burnus T, Hollmann N, Benomar M, Lorenz T, Tanaka A, Lin HJ, Hsieh HH, Chen CT, Tjeng LH. Spin blockade, orbital occupation, and charge ordering in La1.5Sr0.5CoO4. Phys Rev Lett 2009; 102:116401. [PMID: 19392219 DOI: 10.1103/physrevlett.102.116401] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2008] [Indexed: 05/27/2023]
Abstract
Using Co-L2,3 and O-K x-ray absorption spectroscopy, we reveal that the charge ordering in La1.5Sr0.5CoO4 involves high spin (S=3/2) Co2+ and low spin (S=0) Co3+ ions. This provides evidence for the spin-blockade phenomenon as a source for the extremely insulating nature of the La2-xSrxCoO4 series. The associated e{g}{2} and e{g}{0} orbital occupation accounts for the large contrast in the Co-O bond lengths and, in turn, the high charge ordering temperature. Yet, the low magnetic ordering temperature is naturally explained by the presence of the nonmagnetic (S=0) Co3+ ions. From the identification of the bands we infer that La1.5Sr0.5CoO4 is a narrow band material.
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Affiliation(s)
- C F Chang
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, 50937 Köln, Germany
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22
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Wu H, Burnus T, Hu Z, Martin C, Maignan A, Cezar JC, Tanaka A, Brookes NB, Khomskii DI, Tjeng LH. Ising magnetism and ferroelectricity in Ca3CoMnO6. Phys Rev Lett 2009; 102:026404. [PMID: 19257300 DOI: 10.1103/physrevlett.102.026404] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2008] [Indexed: 05/27/2023]
Abstract
The origin of both the Ising chain magnetism and ferroelectricity in Ca3CoMnO6 is studied by ab initio electronic structure calculations and x-ray absorption spectroscopy. We find that Ca3CoMnO6 has alternate trigonal prismatic Co2+ and octahedral Mn4+ sites in the spin chain. Both the Co2+ and Mn4+ are in the high-spin state. In addition, the Co2+ has a huge orbital moment of 1.7micro_{B} which is responsible for the significant Ising magnetism. The centrosymmetric crystal structure known so far is calculated to be unstable with respect to exchange striction in the experimentally observed upward arrow upward arrow downward arrow downward arrow antiferromagnetic structure for the Ising chain. The calculated inequivalence of the Co-Mn distances accounts for the ferroelectricity.
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Affiliation(s)
- Hua Wu
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, 50937 Köln, Germany
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23
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Haverkort MW, Elfimov IS, Tjeng LH, Sawatzky GA, Damascelli A. Strong spin-orbit coupling effects on the Fermi surface of Sr2RuO4 and Sr2RhO4. Phys Rev Lett 2008; 101:026406. [PMID: 18764207 DOI: 10.1103/physrevlett.101.026406] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/29/2008] [Indexed: 05/26/2023]
Abstract
We present a first-principles study of spin-orbit coupling effects on the Fermi surface of Sr2RuO4 and Sr2RhO4. For nearly degenerate bands, spin-orbit coupling leads to a dramatic change of the Fermi surface with respect to nonrelativistic calculations; as evidenced by the comparison with experiments on Sr2RhO4, it cannot be disregarded. For Sr2RuO4, the Fermi surface modifications are more subtle but equally dramatic in the detail: Spin-orbit coupling induces a strong momentum dependence, normal to the RuO2 planes, for both orbital and spin character of the low-energy electronic states. These findings have profound implications for the understanding of unconventional superconductivity in Sr2RuO4.
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Affiliation(s)
- M W Haverkort
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, 50937 Köln, Germany
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24
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Hossain MA, Hu Z, Haverkort MW, Burnus T, Chang CF, Klein S, Denlinger JD, Lin HJ, Chen CT, Mathieu R, Kaneko Y, Tokura Y, Satow S, Yoshida Y, Takagi H, Tanaka A, Elfimov IS, Sawatzky GA, Tjeng LH, Damascelli A. Crystal-field level inversion in lightly Mn-doped Sr3Ru2O7. Phys Rev Lett 2008; 101:016404. [PMID: 18764131 DOI: 10.1103/physrevlett.101.016404] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2008] [Indexed: 05/26/2023]
Abstract
Sr3(Ru(1-x)Mnx)2O7, in which 4d-Ru is substituted by the more localized 3d-Mn, is studied by x-ray dichroism and spin-resolved density functional theory. We find that Mn impurities do not exhibit the same 4+ valence of Ru, but act as 3+ acceptors; the extra eg electron occupies the in-plane 3d(x2-y2) orbital instead of the expected out-of-plane 3d(3z2-r2). We propose that the 3d-4d interplay, via the ligand oxygen orbitals, is responsible for this crystal-field level inversion and the material's transition to an antiferromagnetic, possibly orbitally ordered, low-temperature state.
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Affiliation(s)
- M A Hossain
- Department of Physics & Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
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25
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Hansmann P, Severing A, Hu Z, Haverkort MW, Chang CF, Klein S, Tanaka A, Hsieh HH, Lin HJ, Chen CT, Fåk B, Lejay P, Tjeng LH. Determining the crystal-field ground state in rare earth heavy fermion materials using soft-x-ray absorption spectroscopy. Phys Rev Lett 2008; 100:066405. [PMID: 18352496 DOI: 10.1103/physrevlett.100.066405] [Citation(s) in RCA: 4] [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: 08/28/2007] [Indexed: 05/26/2023]
Abstract
We infer that soft-x-ray absorption spectroscopy is a versatile method for the determination of the crystal-field ground state symmetry of rare earth heavy fermion systems, complementing neutron scattering. Using realistic and universal parameters, we provide a theoretical mapping between the polarization dependence of Ce M(4,5) spectra and the charge distribution of the Ce 4f states. The experimental resolution can be orders of magnitude larger than the 4f crystal-field splitting itself. To demonstrate the experimental feasibility of the method, we investigated CePd2Si2, thereby settling an existing disagreement about its crystal-field ground state.
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Affiliation(s)
- P Hansmann
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, D-50937 Köln, Germany
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26
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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. Phys Rev Lett 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] [What about the content of this article? (0)] [Affiliation(s)] [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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27
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Haverkort MW, Tanaka A, Tjeng LH, Sawatzky GA. Nonresonant inelastic x-ray scattering involving excitonic excitations: the examples of NiO and CoO. Phys Rev Lett 2007; 99:257401. [PMID: 18233556 DOI: 10.1103/physrevlett.99.257401] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2007] [Indexed: 05/25/2023]
Abstract
In a recent publication Larson et al. reported remarkably clear d-d excitations for NiO and CoO with x-ray scattering. Here we present an accurate quantitative description based on a local many body approach, beyond local density approximation + Hubbard U approximations. The magnitude of q[over -->] determines which of the allowed multipoles contributes most to the spectra. The direction of q[over -->] with respect to the crystal can be used as an equivalent to polarization similar to electron energy loss spectroscopy, allowing for a determination of the local symmetry of the initial and final states. This method is more generally applicable and could be a powerful tool for the study of local distortions and symmetries in transition metal and rare earth compounds.
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Affiliation(s)
- M W Haverkort
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, D-50937 Köln, Germany
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Haverkort MW, Hu Z, Cezar JC, Burnus T, Hartmann H, Reuther M, Zobel C, Lorenz T, Tanaka A, Brookes NB, Hsieh HH, Lin HJ, Chen CT, Tjeng LH. Spin state transition in LaCoO3 studied using soft x-ray absorption spectroscopy and magnetic circular dichroism. Phys Rev Lett 2006; 97:176405. [PMID: 17155490 DOI: 10.1103/physrevlett.97.176405] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2006] [Indexed: 05/12/2023]
Abstract
Using soft x-ray absorption spectroscopy and magnetic circular dichroism at the Co-L(2,3) edge, we reveal that the spin state transition in LaCoO3 can be well described by a low-spin ground state and a triply degenerate high-spin first excited state. From the temperature dependence of the spectral line shapes, we find that LaCoO3 at finite temperatures is an inhomogeneous mixed-spin state system. It is crucial that the magnetic circular dichroism signal in the paramagnetic state carries a large orbital momentum. This directly shows that the currently accepted low- or intermediate-spin picture is at variance. Parameters derived from these spectroscopies fully explain existing magnetic susceptibility, electron spin resonance, and inelastic neutron data.
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Affiliation(s)
- M W Haverkort
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany
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29
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Koethe TC, Hu Z, Haverkort MW, Schüssler-Langeheine C, Venturini F, Brookes NB, Tjernberg O, Reichelt W, Hsieh HH, Lin HJ, Chen CT, Tjeng LH. Transfer of spectral weight and symmetry across the metal-insulator transition in VO(2). Phys Rev Lett 2006; 97:116402. [PMID: 17025910 DOI: 10.1103/physrevlett.97.116402] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2006] [Indexed: 05/12/2023]
Abstract
We present a detailed study of the valence and conduction bands of VO2 across the metal-insulator transition using bulk-sensitive photoelectron and O K x-ray absorption spectroscopies. We observe a giant transfer of spectral weight with distinct features that require an explanation which goes beyond the Peierls transition model as well as the standard single-band Hubbard model. Analysis of the symmetry and energies of the bands reveals the decisive role of the V 3d orbital degrees of freedom. Comparison to recent realistic many body calculations shows that much of the k dependence of the self-energy correction can be cast within a dimer model.
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Affiliation(s)
- T C Koethe
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, D-50937 Köln, Germany
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30
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Wu H, Hu Z, Burnus T, Denlinger JD, Khalifah PG, Mandrus DG, Jang LY, Hsieh HH, Tanaka A, Liang KS, Allen JW, Cava RJ, Khomskii DI, Tjeng LH. Orbitally driven spin-singlet dimerization in S=1 La4Ru2O10. Phys Rev Lett 2006; 96:256402. [PMID: 16907328 DOI: 10.1103/physrevlett.96.256402] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2006] [Indexed: 05/11/2023]
Abstract
Using x-ray absorption spectroscopy at the Ru-L2,3 edge we reveal that the Ru4+ ions remain in the S=1 spin state across the rare 4d-orbital ordering transition and spin-gap formation. We find using local spin density approximation + Hubbard U band structure calculations that the crystal fields in the low-temperature phase are not strong enough to stabilize the S=0 state. Instead, we identify a distinct orbital ordering with a significant anisotropy of the antiferromagnetic exchange couplings. We conclude that La4Ru2O10 appears to be a novel material in which the orbital physics drives the formation of spin-singlet dimers in a quasi-two-dimensional S=1 system.
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Affiliation(s)
- Hua Wu
- II. Physikalisches Institut, Universität zu Köln, 50937 Köln, Germany
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31
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Haverkort MW, Hu Z, Tanaka A, Reichelt W, Streltsov SV, Korotin MA, Anisimov VI, Hsieh HH, Lin HJ, Chen CT, Khomskii DI, Tjeng LH. Orbital-assisted metal-insulator transition in VO2. Phys Rev Lett 2005; 95:196404. [PMID: 16384003 DOI: 10.1103/physrevlett.95.196404] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2005] [Indexed: 05/05/2023]
Abstract
We found direct experimental evidence for an orbital switching in the V 3d states across the metal-insulator transition in VO2. We have used soft-x-ray absorption spectroscopy at the V L2,3 edges as a sensitive local probe and have determined quantitatively the orbital polarizations. These results strongly suggest that, in going from the metallic to the insulating state, the orbital occupation changes in a manner that charge fluctuations and effective bandwidths are reduced, that the system becomes more one dimensional and more susceptible to a Peierls-like transition, and that the required massive orbital switching can only be made if the system is close to a Mott insulating regime.
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Affiliation(s)
- M W Haverkort
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, D-50937 Köln, Germany
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32
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Abstract
We find using local spin density approximation + Hubbard U band structure calculations that the novel one-dimensional cobaltate Ca3Co2O6 is not a ferromagnetic half-metal but a Mott insulator. Both the octahedral and the trigonal Co ions are formally trivalent, with the octahedral being in the low-spin and the trigonal in the high-spin state. The inclusion of the spin-orbit coupling leads to the occupation of the minority-spin d2 orbital for the unusually coordinated trigonal Co, producing a giant orbital moment (1.57 microB). It also results in an anomalously large magnetocrystalline anisotropy (of order 70 meV), elucidating why the magnetism is highly Ising-like. The role of the oxygen holes, carrying an induced magnetic moment of 0.13 microB per oxygen, for the exchange interactions is discussed.
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Affiliation(s)
- Hua Wu
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, D-50937 Köln, Germany
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33
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Csiszar SI, Haverkort MW, Hu Z, Tanaka A, Hsieh HH, Lin HJ, Chen CT, Hibma T, Tjeng LH. Controlling orbital moment and spin orientation in CoO layers by strain. Phys Rev Lett 2005; 95:187205. [PMID: 16383942 DOI: 10.1103/physrevlett.95.187205] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2004] [Indexed: 05/05/2023]
Abstract
We have observed that CoO films grown on different substrates show dramatic differences in their magnetic properties. Using polarization dependent x-ray absorption spectroscopy at the Co L2,3 edges, we revealed that the magnitude and orientation of the magnetic moments strongly depend on the strain in the films induced by the substrate. We presented a quantitative model to explain how strain together with the spin-orbit interaction determine the 3d orbital occupation, the magnetic anisotropy, as well as the spin and orbital contributions to the magnetic moments. Control over the sign and direction of the strain may, therefore, open new opportunities for applications in the field of exchange bias in multilayered magnetic films.
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Affiliation(s)
- S I Csiszar
- Materials Science Center, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
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34
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Schüssler-Langeheine C, Schlappa J, Tanaka A, Hu Z, Chang CF, Schierle E, Benomar M, Ott H, Weschke E, Kaindl G, Friedt O, Sawatzky GA, Lin HJ, Chen CT, Braden M, Tjeng LH. Spectroscopy of stripe order in La1.8Sr0.2NiO4 using resonant soft x-ray diffraction. Phys Rev Lett 2005; 95:156402. [PMID: 16241744 DOI: 10.1103/physrevlett.95.156402] [Citation(s) in RCA: 6] [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: 02/15/2005] [Indexed: 05/05/2023]
Abstract
Strong resonant enhancements of the charge-order and spin-order superstructure-diffraction intensities in La1.8Sr0.2NiO4 are observed when x-ray energies in the vicinity of the Ni L2,3 absorption edges are used. The pronounced photon-energy and polarization dependences of these diffraction intensities allow for a critical determination of the local symmetry of the ordered spin and charge carriers. We found that not only the antiferromagnetic order but also the charge-order superstructure resides within the NiO2 layers; the holes are mainly located on in-plane oxygens surrounding a Ni2+ site with the spins coupled antiparallel in close analogy to Zhang-Rice singlets in the cuprates.
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Affiliation(s)
- C Schüssler-Langeheine
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, D-50937 Köln, Germany
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35
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Haverkort MW, Hu Z, Tanaka A, Ghiringhelli G, Roth H, Cwik M, Lorenz T, Schüssler-Langeheine C, Streltsov SV, Mylnikova AS, Anisimov VI, de Nadai C, Brookes NB, Hsieh HH, Lin HJ, Chen CT, Mizokawa T, Taguchi Y, Tokura Y, Khomskii DI, Tjeng LH. Determination of the orbital moment and crystal-field splitting in LaTiO3. Phys Rev Lett 2005; 94:056401. [PMID: 15783666 DOI: 10.1103/physrevlett.94.056401] [Citation(s) in RCA: 5] [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: 04/23/2004] [Indexed: 05/24/2023]
Abstract
Utilizing a sum rule in a spin-resolved photoelectron spectroscopic experiment with circularly polarized light, we show that the orbital moment in LaTiO3 is strongly reduced from its ionic value, both below and above the Ne el temperature. Using Ti L2,3 x-ray absorption spectroscopy as a local probe, we found that the crystal-field splitting in the t2g subshell is about 0.12-0.30 eV. This large splitting does not facilitate the formation of an orbital liquid.
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Affiliation(s)
- M W Haverkort
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, D-50937 Köln, Germany
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36
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Schlappa J, Schüssler-Langeheine C, Scherer R, Tjeng LH. Comment on "temperature-dependent fermi gap opening in the c(6x4)-C60/Ag001 two-dimensional superstructure". Phys Rev Lett 2004; 93:119701-119702. [PMID: 15447386 DOI: 10.1103/physrevlett.93.119701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2003] [Indexed: 05/24/2023]
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37
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Hu Z, Wu H, Haverkort MW, Hsieh HH, Lin HJ, Lorenz T, Baier J, Reichl A, Bonn I, Felser C, Tanaka A, Chen CT, Tjeng LH. Different look at the spin state of Co(3+) ions in a CoO(5) pyramidal coordination. Phys Rev Lett 2004; 92:207402. [PMID: 15169382 DOI: 10.1103/physrevlett.92.207402] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2003] [Indexed: 05/24/2023]
Abstract
Using soft-x-ray absorption spectroscopy at the Co L(2,3) and O K edges, we demonstrate that the Co3+ ions with the CoO5 pyramidal coordination in the layered Sr2CoO3Cl compound are unambiguously in the high spin state. Our result questions the reliability of the spin state assignments made so far for the recently synthesized layered cobalt perovskites and calls for a reexamination of the modeling for the complex and fascinating properties of these new materials.
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Affiliation(s)
- Z Hu
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, 50937 Köln, Germany
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38
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Steeneken PG, Tjeng LH, Sawatzky GA, Tanaka A, Tjernberg O, Ghiringhelli G, Brookes NB, Nugroho AA, Menovsky AA. Crossing the gap from p- to n-type doping: nature of the states near the chemical potential in La(2)-(x)Sr(x)CuO(4) and Nd(2-x)Ce(x)CuO(4-delta). Phys Rev Lett 2003; 90:247005. [PMID: 12857219 DOI: 10.1103/physrevlett.90.247005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2003] [Indexed: 05/24/2023]
Abstract
We report on an x-ray absorption and resonant photoemission study on single crystals of the high-T(c) cuprates La2-xSrxCuO4 and Nd(2-x)Ce(x)CuO(4-delta). Using an intrinsic energy reference, we find that the chemical potential of La2-xSrxCuO4 lies near the top of the La2CuO4 valence band whereas in Nd(2-x)Ce(x)CuO(4-delta) it is situated near the bottom of the Nd2CuO4 conduction band. The data clearly establish that the introduction of Ce in Nd2CuO4 results in electrons being doped into the CuO2 planes. We infer that the states closest to the chemical potential have a Cu 3d(10) singlet origin in Nd(2-x)Ce(x)CuO(4-delta) and a 3d(9)L singlet origin in La2-xSrxCuO4.
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Affiliation(s)
- P G Steeneken
- MSC, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
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39
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Steeneken PG, Tjeng LH, Elfimov I, Sawatzky GA, Ghiringhelli G, Brookes NB, Huang DJ. Exchange splitting and charge carrier spin polarization in EuO. Phys Rev Lett 2002; 88:047201. [PMID: 11801161 DOI: 10.1103/physrevlett.88.047201] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2001] [Indexed: 05/23/2023]
Abstract
High quality thin films of the ferromagnetic semiconductor EuO have been prepared and were studied using a new form of spin-resolved spectroscopy. We observed large changes in the electronic structure across the Curie and metal-insulator transition temperature. We found that these are caused by the exchange splitting of the conduction band in the ferromagnetic state, which is as large as 0.6 eV. We also present strong evidence that the bottom of the conduction band consists mainly of majority spins. This implies that doped charge carriers in EuO are practically fully spin polarized.
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Affiliation(s)
- P G Steeneken
- Solid State Physics Laboratory, Materials Science Centre, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
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40
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Brookes NB, Ghiringhelli G, Tjernberg O, Tjeng LH, Mizokawa T, Li TW, Menovsky AA. Detection of Zhang-Rice singlets using spin-polarized photoemission. Phys Rev Lett 2001; 87:237003. [PMID: 11736472 DOI: 10.1103/physrevlett.87.237003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2000] [Indexed: 05/23/2023]
Abstract
From a spin-resolved photoemission study on the Bi(2)Sr(2)CaCu(2)O(8+delta) superconductor, we show experimentally that the first ionization state is of nearly pure singlet character. This is true both above and below the superconducting transition and in the presence of doping and band formation. This provides direct support for the existence and stability of Zhang-Rice singlets in high-temperature superconductors, justifying the ansatz of single-band models. Moreover, we establish this technique as an important probe for a wide range of cuprates and strongly correlated materials.
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Affiliation(s)
- N B Brookes
- European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble, France
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41
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Mizokawa T, Tjeng LH, Sawatzky GA, Ghiringhelli G, Tjernberg O, Brookes NB, Fukazawa H, Nakatsuji S, Maeno Y. Spin-orbit coupling in the Mott insulator Ca(2)RuO(4). Phys Rev Lett 2001; 87:077202. [PMID: 11497913 DOI: 10.1103/physrevlett.87.077202] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2000] [Indexed: 05/23/2023]
Abstract
O 1s x-ray absorption study of the Mott insulator Ca(2)RuO(4) shows that the orbital population of the 4d t(2g) band dramatically changes with temperature. In addition, spin-resolved circularly polarized photoemission study of Ca(2)RuO(4) shows that a substantial orbital angular momentum is induced in the Ru 4d t(2g) band. Based on the experimental results and model Hartree-Fock calculations, we argue that the cooperation between the strong spin-orbit coupling in the Ru 4d t(2g) band and the small distortion of the RuO(6) octahedra causes the interesting changeover of the spin and orbital anisotropy as a function of temperature.
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Affiliation(s)
- T Mizokawa
- Department of Complexity Science and Engineering, University of Tokyo, Tokyo 113-0033, Japan
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42
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Hesper R, Tjeng LH, Heeres A, Sawatzky GA. BCS-like density of states in superconducting A3C60 surfaces. Phys Rev Lett 2000; 85:1970-1973. [PMID: 10970660 DOI: 10.1103/physrevlett.85.1970] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2000] [Indexed: 05/23/2023]
Abstract
We report on an ultrahigh resolution photoemission study on the topmost molecular layer of K3C60 and Rb3C60 films below and above the superconducting transition temperature T(C). We observed not only clear evidence for the opening of the superconducting gap, but also a modification in the photoemission line shape consistent with a change from a normal-metallic to a BCS-like density of states, including the formation of a condensation peak. The data can be accurately modeled by a BCS-type function with a gap Delta derived from T(C) in the weak-coupling limit ( 2Delta/k(B)T(C) = 3.53).
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Affiliation(s)
- R Hesper
- Solid State Physics Laboratory, Materials Science Centre, University of Groningen, Nijenborgh 4, 9747 AG Groningen, the Netherlands
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43
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Pellegrin E, Tjeng LH, de Groot FM, Hesper R, Sawatzky GA, Moritomo Y, Tokura Y. Soft X-Ray Magnetic Circular Dichroism Study of the Colossal Magnetoresistance Compound La1-xSrxMnO3. ACTA ACUST UNITED AC 1997. [DOI: 10.1051/jp4/1997030] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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44
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Abbate M, Potze R, Sawatzky GA, Schlenker C, Lin HJ, Tjeng LH, Chen CT, Teehan D, Turner TS. Changes in the electronic structure of Ti4O7 across the semiconductor-semiconductor-metal transitions. Phys Rev B Condens Matter 1995; 51:10150-10153. [PMID: 9977690 DOI: 10.1103/physrevb.51.10150] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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45
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Meinders MB, Tjeng LH, Sawatzky GA. Comment on "C 1s autoionization study of electron hopping rates in solid C60". Phys Rev Lett 1994; 73:2937. [PMID: 10057238 DOI: 10.1103/physrevlett.73.2937] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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46
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Tjeng LH, Oh S, Chen CT, Allen JW, Cox DL. Tjeng et al. reply. Phys Rev Lett 1994; 72:4154. [PMID: 10056396 DOI: 10.1103/physrevlett.72.4154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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47
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48
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Tjeng LH, Chen CT, Rudolf P, Meigs G, Thole BT. Magnetic circularly polarized 2p resonant photoemission of nickel. Phys Rev B Condens Matter 1993; 48:13378-13382. [PMID: 10007732 DOI: 10.1103/physrevb.48.13378] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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49
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van Elp J, George SJ, Chen J, Peng G, Chen CT, Tjeng LH, Meigs G, Lin HJ, Zhou ZH, Adams MW. Soft x-ray magnetic circular dichroism: a probe for studying paramagnetic bioinorganic systems. Proc Natl Acad Sci U S A 1993; 90:9664-7. [PMID: 8415759 PMCID: PMC47630 DOI: 10.1073/pnas.90.20.9664] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Soft x-ray magnetic circular dichroism was used to study a paramagnetic bioinogranic system. We measured the Fe L edges of Pyrococcus furiosus rubredoxin, using circularly polarized synchrotron radiation, a split-coil super-conducting magnet, low sample temperatures, and fluorescence detection. The observed dichroism effect is strong (30%) and in general agreement with the calculation. The method is element- and oxidation state-specific, and the data can be interpreted by established theoretical procedures. Soft x-ray magnetic circular dichroism demonstrates enormous potential as a probe for studying paramagnetic systems in biology, chemistry, and material science.
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Affiliation(s)
- J van Elp
- Energy and Environment Division, Lawrence Berkeley Laboratory, CA 94720
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50
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Tjeng LH, Oh S, Cho E, Lin H, Chen CT, Gweon G, Park J, Allen JW, Suzuki T, Makivic MS, Cox DL. Temperature dependence of the Kondo resonance in YbAl3. Phys Rev Lett 1993; 71:1419-1422. [PMID: 10055535 DOI: 10.1103/physrevlett.71.1419] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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