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Li Y, Bachus S, Liu B, Radelytskyi I, Bertin A, Schneidewind A, Tokiwa Y, Tsirlin AA, Gegenwart P. Rearrangement of Uncorrelated Valence Bonds Evidenced by Low-Energy Spin Excitations in YbMgGaO_{4}. Phys Rev Lett 2019; 122:137201. [PMID: 31012603 DOI: 10.1103/physrevlett.122.137201] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Indexed: 05/02/2023]
Abstract
dc-magnetization data measured down to 40 mK speak against conventional freezing and reinstate YbMgGaO_{4} as a triangular spin-liquid candidate. Magnetic susceptibility measured parallel and perpendicular to the c axis reaches constant values below 0.1 and 0.2 K, respectively, thus indicating the presence of gapless low-energy spin excitations. We elucidate their nature in the triple-axis inelastic neutron scattering experiment that pinpoints the low-energy (E≤J_{0}∼0.2 meV) part of the excitation continuum present at low temperatures (T<J_{0}/k_{B}), but completely disappearing upon warming the system above T≫J_{0}/k_{B}. In contrast to the high-energy part at E>J_{0} that is rooted in the breaking of nearest-neighbor valence bonds and persists to temperatures well above J_{0}/k_{B}, the low-energy one originates from the rearrangement of the valence bonds and thus from the propagation of unpaired spins. We further extend this picture to herbertsmithite, the spin-liquid candidate on the kagome lattice, and argue that such a hierarchy of magnetic excitations may be a universal feature of quantum spin liquids.
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Affiliation(s)
- Yuesheng Li
- Experimental Physics VI, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany
| | - Sebastian Bachus
- Experimental Physics VI, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany
| | - Benqiong Liu
- Key Laboratory of Neutron Physics, Institute of Nuclear Physics and Chemistry, CAEP, Mianyang 621900, People's Republic of China
- Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Forschungszentrum Jülich GmbH, Lichtenbergstrasse 1, 85748 Garching, Germany
| | - Igor Radelytskyi
- Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Forschungszentrum Jülich GmbH, Lichtenbergstrasse 1, 85748 Garching, Germany
| | - Alexandre Bertin
- Institut fuer Festkörperphysik, TU Dresden, D-01062, Dresden, Germany
| | - Astrid Schneidewind
- Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Forschungszentrum Jülich GmbH, Lichtenbergstrasse 1, 85748 Garching, Germany
| | - Yoshifumi Tokiwa
- Experimental Physics VI, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany
| | - Alexander A Tsirlin
- Experimental Physics VI, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany
| | - Philipp Gegenwart
- Experimental Physics VI, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany
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Abstract
The pyrochlore structure (A2B2O7) has been an object of consistent study by materials scientists largely due to the stability of the cubic lattice with respect to a wide variety of chemical species on the A or B sites. The criterion for stability under ambient conditions is controlled by the ratio of these cations, which is empirically 1.36 < RA/RB < 1.71. However, under applied pressure synthesis conditions, the pyrochlore lattice is stable up to RA/RB ∼ 2.30, opening up possibilities for new compounds. In this review, we will highlight recent work in exploring new rare-earth pyrochlores such as the germanates RE2Ge2O7 and platinates RE2Pt2O7. We highlight recent discoveries made in these pyrochlores such as highly correlated spin ice behavior, spin liquid ground states, and exotic magnetic ordering.
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Lhotel E, Petit S, Ciomaga Hatnean M, Ollivier J, Mutka H, Ressouche E, Lees MR, Balakrishnan G. Evidence for dynamic kagome ice. Nat Commun 2018; 9:3786. [PMID: 30224640 PMCID: PMC6141606 DOI: 10.1038/s41467-018-06212-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [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: 11/24/2017] [Accepted: 08/03/2018] [Indexed: 11/09/2022] Open
Abstract
The search for two-dimensional quantum spin liquids, exotic magnetic states remaining disordered down to zero temperature, has been a great challenge in frustrated magnetism over the last few decades. Recently, evidence for fractionalized excitations, called spinons, emerging from these states has been observed in kagome and triangular antiferromagnets. In contrast, quantum ferromagnetic spin liquids in two dimensions, namely quantum kagome ices, have been less investigated, yet their classical counterparts exhibit amazing properties, magnetic monopole crystals as well as magnetic fragmentation. Here, we show that applying a magnetic field to the pyrochlore oxide Nd2Zr2O7, which has been shown to develop three-dimensional quantum magnetic fragmentation in zero field, results in a dimensional reduction, creating a dynamic kagome ice state: the spin excitation spectrum determined by neutron scattering encompasses a flat mode with a six arm shape akin to the kagome ice structure factor, from which dispersive branches emerge.
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Affiliation(s)
- E Lhotel
- Institut Néel CNRS, Université Grenoble Alpes, 38042, Grenoble, France.
| | - S Petit
- Laboratoire Léon Brillouin, CEA CNRS Université Paris Saclay, CE-Saclay, 91191, Gif-sur-Yvette, France.
| | | | - J Ollivier
- Institut Laue Langevin, F-38042, Grenoble, France
| | - H Mutka
- Institut Laue Langevin, F-38042, Grenoble, France
| | - E Ressouche
- INAC, CEA, Université Grenoble Alpes, CEA Grenoble, F-38054, Grenoble, France
| | - M R Lees
- Department of Physics, University of Warwick, Coventry, CV4 7AL, UK
| | - G Balakrishnan
- Department of Physics, University of Warwick, Coventry, CV4 7AL, UK
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Petit S, Guitteny S, Robert J, Bonville P, Decorse C, Ollivier J, Mutka H, Mirebeau I. Spin dynamics in highly frustrated pyrochlore magnets. EPJ Web of Conferences 2015. [DOI: 10.1051/epjconf/20158303012] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Hallas AM, Cheng JG, Arevalo-Lopez AM, Silverstein HJ, Su Y, Sarte PM, Zhou HD, Choi ES, Attfield JP, Luke GM, Wiebe CR. Incipient ferromagnetism in Tb2Ge2O7: application of chemical pressure to the enigmatic spin-liquid compound Tb2Ti2O7. Phys Rev Lett 2014; 113:267205. [PMID: 25615381 DOI: 10.1103/physrevlett.113.267205] [Citation(s) in RCA: 3] [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: 04/24/2014] [Indexed: 06/04/2023]
Abstract
After nearly 20 years of study, the origin of the spin-liquid state in Tb2Ti2O7 remains a challenge for experimentalists and theorists alike. To improve our understanding of the exotic magnetism in Tb2Ti2O7, we synthesize a chemical pressure analog: Tb2Ge2O7. Substitution of titanium by germanium results in a lattice contraction and enhanced exchange interactions. We characterize the magnetic ground state of Tb2Ge2O7 with specific heat, ac and dc magnetic susceptibility, and polarized neutron scattering measurements. Akin to Tb2Ti2O7, there is no long-range order in Tb2Ge2O7 down to 20 mK. The Weiss temperature of -19.2(1) K, which is more negative than that of Tb2Ti2O7, supports the picture of stronger antiferromagnetic exchange. Polarized neutron scattering of Tb2Ge2O7 reveals that liquidlike correlations dominate in this system at 3.5 K. However, below 1 K, the liquidlike correlations give way to intense short-range ferromagnetic correlations with a length scale similar to the Tb-Tb nearest neighbor distance. Despite stronger antiferromagnetic exchange, the ground state of Tb2Ge2O7 has ferromagnetic character, in stark contrast to the pressure-induced antiferromagnetic order observed in Tb2Ti2O7.
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Affiliation(s)
- A M Hallas
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4M1, Canada
| | - J G Cheng
- Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - A M Arevalo-Lopez
- Centre for Science at Extreme Conditions and School of Chemistry, University of Edinburgh, King's Buildings, Mayfield Road, Edinburgh EH9 3JZ, United Kingdom
| | - H J Silverstein
- Department of Chemistry, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada
| | - Y Su
- Jülich Centre for Neutron Science, Forschungszentrum Jülich GmbH, Outstation at MLZ, Lichtenbergstrasse 1, 85747 Garching, Germany
| | - P M Sarte
- Department of Chemistry, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada
| | - H D Zhou
- Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996-1200, USA and National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32306-4005, USA
| | - E S Choi
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32306-4005, USA
| | - J P Attfield
- Centre for Science at Extreme Conditions and School of Chemistry, University of Edinburgh, King's Buildings, Mayfield Road, Edinburgh EH9 3JZ, United Kingdom
| | - G M Luke
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4M1, Canada and Canadian Institute for Advanced Research, Toronto, Ontario M5G 1Z7, Canada
| | - C R Wiebe
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4M1, Canada and Department of Chemistry, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada and Department of Chemistry, University of Winnipeg, Winnipeg, Manitoba R3B 2E9, Canada
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Abstract
The spin ice materials, including Ho2Ti2O7 and Dy2Ti2O7, are rare-earth pyrochlore magnets which, at low temperatures, enter a constrained paramagnetic state with an emergent gauge freedom. Spin ices provide one of very few experimentally realized examples of fractionalization because their elementary excitations can be regarded as magnetic monopoles and, over some temperature range, spin ice materials are best described as liquids of these emergent charges. In the presence of quantum fluctuations, one can obtain, in principle, a quantum spin liquid descended from the classical spin ice state characterized by emergent photon-like excitations. Whereas in classical spin ices the excitations are akin to electrostatic charges with a mutual Coulomb interaction, in the quantum spin liquid these charges interact through a dynamic and emergent electromagnetic field. In this review, we describe the latest developments in the study of such a quantum spin ice, focusing on the spin liquid phenomenology and the kinds of materials where such a phase might be found.
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Affiliation(s)
- M J P Gingras
- Department of Physics and Astronomy, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, N2L 3G1, Canada. Perimeter Institute for Theoretical Physics, 31 Caroline North, Waterloo, Ontario, N2L 2Y5, Canada. Canadian Institute for Advanced Research, Toronto, Ontario, M5G 1Z8, Canada
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7
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Mun ED, Chern GW, Pardo V, Rivadulla F, Sinclair R, Zhou HD, Zapf VS, Batista CD. Magnetic field induced transition in vanadium spinels. Phys Rev Lett 2014; 112:017207. [PMID: 24483929 DOI: 10.1103/physrevlett.112.017207] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2013] [Indexed: 06/03/2023]
Abstract
We study vanadium spinels AV2O4 (A = Cd,Mg) in pulsed magnetic fields up to 65 T. A jump in magnetization at μ0H≈40 T is observed in the single-crystal MgV2O4, indicating a field induced quantum phase transition between two distinct magnetic orders. In the multiferroic CdV2O4, the field induced transition is accompanied by a suppression of the electric polarization. By modeling the magnetic properties in the presence of strong spin-orbit coupling characteristic of vanadium spinels, we show that both features of the field induced transition can be successfully explained by including the effects of the local trigonal crystal field.
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Affiliation(s)
- E D Mun
- NHMFL Materials Physics and Applications, T-4 and CNLS, Los Alamos Laboratory (LANL), Los Alamos, New Mexico 87545, USA
| | - Gia-Wei Chern
- Theoretical Division, T-4 and CNLS, Los Alamos Laboratory, Los Alamos, New Mexico 87545, USA
| | - V Pardo
- Departamento de Fisica Aplicada, Universidad de Santiago de Compostela, 15782 Santiago de Compostela, Spain
| | - F Rivadulla
- CIQUS, Universidad de Santiago de Compostela, 15782 Santiago de Compostela, Spain
| | - R Sinclair
- Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996-1200, USA
| | - H D Zhou
- Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996-1200, USA
| | - V S Zapf
- NHMFL Materials Physics and Applications, T-4 and CNLS, Los Alamos Laboratory (LANL), Los Alamos, New Mexico 87545, USA
| | - C D Batista
- Theoretical Division, T-4 and CNLS, Los Alamos Laboratory, Los Alamos, New Mexico 87545, USA
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Fennell T, Kenzelmann M, Roessli B, Mutka H, Ollivier J, Ruminy M, Stuhr U, Zaharko O, Bovo L, Cervellino A, Haas MK, Cava RJ. Magnetoelastic excitations in the pyrochlore spin liquid Tb2Ti2O7. Phys Rev Lett 2014; 112:017203. [PMID: 24483925 DOI: 10.1103/physrevlett.112.017203] [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: 05/22/2013] [Indexed: 06/03/2023]
Abstract
At low temperatures, Tb2Ti2O7 enters a spin liquid state, despite expectations of magnetic order and/or a structural distortion. Using neutron scattering, we have discovered that in this spin liquid state an excited crystal field level is coupled to a transverse acoustic phonon, forming a hybrid excitation. Magnetic and phononlike branches with identical dispersion relations can be identified, and the hybridization vanishes in the paramagnetic state. We suggest that Tb2Ti2O7 is aptly named a "magnetoelastic spin liquid" and that the hybridization of the excitations suppresses both magnetic ordering and the structural distortion. The spin liquid phase of Tb2Ti2O7 can now be regarded as a Coulomb phase with propagating bosonic spin excitations.
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Affiliation(s)
- T Fennell
- Laboratory for Neutron Scattering, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
| | - M Kenzelmann
- Laboratory for Developments and Methods, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
| | - B Roessli
- Laboratory for Neutron Scattering, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
| | - H Mutka
- Institut Laue Langevin, BP 156, 6, rue Jules Horowitz, 38042 Grenoble Cedex 9, France
| | - J Ollivier
- Institut Laue Langevin, BP 156, 6, rue Jules Horowitz, 38042 Grenoble Cedex 9, France
| | - M Ruminy
- Laboratory for Neutron Scattering, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
| | - U Stuhr
- Laboratory for Neutron Scattering, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
| | - O Zaharko
- Laboratory for Neutron Scattering, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
| | - L Bovo
- London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, 17-19 Gordon Street, London WC1H 0AH, United Kingdom
| | - A Cervellino
- Swiss Light Source, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
| | - M K Haas
- Department of Chemistry, Princeton University, Princeton, New Jersey 08540, USA
| | - R J Cava
- Department of Chemistry, Princeton University, Princeton, New Jersey 08540, USA
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9
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Guitteny S, Robert J, Bonville P, Ollivier J, Decorse C, Steffens P, Boehm M, Mutka H, Mirebeau I, Petit S. Anisotropic propagating excitations and quadrupolar effects in Tb2Ti2O7. Phys Rev Lett 2013; 111:087201. [PMID: 24010468 DOI: 10.1103/physrevlett.111.087201] [Citation(s) in RCA: 4] [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: 05/02/2013] [Revised: 07/05/2013] [Indexed: 06/02/2023]
Abstract
The dynamical magnetic correlations in Tb2Ti2O7 have been investigated using polarized inelastic neutron scattering. Dispersive excitations are observed, emerging from pinch points in reciprocal space and characterized by an anisotropic spectral weight. Anomalies in the crystal field and phonon excitation spectrum at Brillouin zone centers are also reported. These findings suggest that Coulomb phases, although they present a disordered ground state with dipolar correlations, allow the propagation of collective excitations. They also point out a strong spin-lattice coupling, which likely drives effective interactions between the 4f quadrupolar moments.
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Affiliation(s)
- Solène Guitteny
- Laboratoire Léon Brillouin, CEA Saclay, Bâtiment 563, 91191 Gif-sur-Yvette Cedex, France
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