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Weber T, Fobes DM, Waizner J, Steffens P, Tucker GS, Böhm M, Beddrich L, Franz C, Gabold H, Bewley R, Voneshen D, Skoulatos M, Georgii R, Ehlers G, Bauer A, Pfleiderer C, Böni P, Janoschek M, Garst M. Topological magnon band structure of emergent Landau levels in a skyrmion lattice. Science 2022; 375:1025-1030. [PMID: 35239388 DOI: 10.1126/science.abe4441] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The motion of a spin excitation across topologically nontrivial magnetic order exhibits a deflection that is analogous to the effect of the Lorentz force on an electrically charged particle in an orbital magnetic field. We used polarized inelastic neutron scattering to investigate the propagation of magnons (i.e., bosonic collective spin excitations) in a lattice of skyrmion tubes in manganese silicide. For wave vectors perpendicular to the skyrmion tubes, the magnon spectra are consistent with the formation of finely spaced emergent Landau levels that are characteristic of the fictitious magnetic field used to account for the nontrivial topological winding of the skyrmion lattice. This provides evidence of a topological magnon band structure in reciprocal space, which is borne out of the nontrivial real-space topology of a magnetic order.
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Affiliation(s)
- T Weber
- Institut Laue-Langevin, CS 20156, 38042 Grenoble Cedex 9, France
| | - D M Fobes
- Los Alamos National Laboratory, Los Alamos, NM, USA
| | - J Waizner
- Institut für Theoretische Physik, Universität zu Köln, 50937 Köln, Germany
| | - P Steffens
- Institut Laue-Langevin, CS 20156, 38042 Grenoble Cedex 9, France
| | - G S Tucker
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, CH-5232 Villigen, Switzerland.,Laboratory for Quantum Magnetism, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
| | - M Böhm
- Institut Laue-Langevin, CS 20156, 38042 Grenoble Cedex 9, France
| | - L Beddrich
- Physik-Department, Technische Universität München, 85748 Garching, Germany.,MLZ, Technische Universität München, 85748 Garching, Germany
| | - C Franz
- Physik-Department, Technische Universität München, 85748 Garching, Germany.,MLZ, Technische Universität München, 85748 Garching, Germany
| | - H Gabold
- Physik-Department, Technische Universität München, 85748 Garching, Germany.,MLZ, Technische Universität München, 85748 Garching, Germany
| | - R Bewley
- ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot OX11 0QX, UK
| | - D Voneshen
- ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot OX11 0QX, UK.,Department of Physics, Royal Holloway University of London, Egham TW20 0EX, UK
| | - M Skoulatos
- Physik-Department, Technische Universität München, 85748 Garching, Germany.,MLZ, Technische Universität München, 85748 Garching, Germany
| | - R Georgii
- Physik-Department, Technische Universität München, 85748 Garching, Germany.,MLZ, Technische Universität München, 85748 Garching, Germany
| | - G Ehlers
- Neutron Technologies Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - A Bauer
- Physik-Department, Technische Universität München, 85748 Garching, Germany.,Centre for Quantum Engineering (ZQE), Technische Universität München, 85748 Garching, Germany
| | - C Pfleiderer
- Physik-Department, Technische Universität München, 85748 Garching, Germany.,Centre for Quantum Engineering (ZQE), Technische Universität München, 85748 Garching, Germany.,MCQST, Technische Universität München, 85748 Garching, Germany
| | - P Böni
- Physik-Department, Technische Universität München, 85748 Garching, Germany
| | - M Janoschek
- Los Alamos National Laboratory, Los Alamos, NM, USA.,Laboratory for Neutron and Muon Instrumentation (LIN), Paul Scherrer Institute, CH-5232 Villigen, Switzerland.,Physik-Institut, Universität Zürich, CH-8057 Zürich, Switzerland
| | - M Garst
- Institut für Theoretische Physik, Universität zu Köln, 50937 Köln, Germany.,Institut für Theoretische Physik, Technische Universität Dresden, 01062 Dresden, Germany.,Institut für Theoretische Festkörperphysik, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany.,Institute for Quantum Materials and Technology, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
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Podlesnyak A, Nikitin SE, Ehlers G. Low-energy spin dynamics in rare-earth perovskite oxides. J Phys Condens Matter 2021; 33:403001. [PMID: 34252895 DOI: 10.1088/1361-648x/ac1367] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Accepted: 07/12/2021] [Indexed: 06/13/2023]
Abstract
We review recent studies of spin dynamics in rare-earth orthorhombic perovskite oxides of the type RMO3, where R is a rare-earth ion and M is a transition-metal ion, using single-crystal inelastic neutron scattering (INS). After a short introduction to the magnetic INS technique in general, the results of INS experiments on both transition-metal and rare-earth subsystems for four selected compounds (YbFeO3, TmFeO3, YFeO3, YbAlO3) are presented. We show that the spectrum of magnetic excitations consists of two types of collective modes that are well separated in energy: gapped magnons with a typical bandwidth of <70 meV, associated with the antiferromagnetically (AFM) ordered transition-metal subsystem, and AFM fluctuations of <5 meV within the rare-earth subsystem, with no hybridization of those modes. We discuss the high-energy conventional magnon excitations of the 3dsubsystem only briefly, and focus in more detail on the spectacular dynamics of the rare-earth sublattice in these materials. We observe that the nature of the ground state and the low-energy excitation strongly depends on the identity of the rare-earth ion. In the case of non-Kramers ions, the low-symmetry crystal field completely eliminates the degeneracy of the multiplet state, creating a rich magnetic field-temperature phase diagram. In the case of Kramers ions, the resulting ground state is at least a doublet, which can be viewed as an effective quantum spin-1/2. Equally important is the fact that in Yb-based materials the nearest-neighbor exchange interaction dominates in one direction, despite the three-dimensional nature of the orthoperovskite crystal structure. The observation of a fractional spinon continuum and quantum criticality in YbAlO3demonstrates that Kramers rare-earth based magnets can provide realizations of various aspects of quantum low-dimensional physics.
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Affiliation(s)
- A Podlesnyak
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States of America
| | - S E Nikitin
- Paul Scherrer Institute, CH-5232 Villigen, Switzerland
| | - G Ehlers
- Neutron Technologies Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States of America
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3
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Lanigan-Atkins T, Yang S, Niedziela JL, Bansal D, May AF, Puretzky AA, Lin JYY, Pajerowski DM, Hong T, Chi S, Ehlers G, Delaire O. Extended anharmonic collapse of phonon dispersions in SnS and SnSe. Nat Commun 2020; 11:4430. [PMID: 32887880 PMCID: PMC7474096 DOI: 10.1038/s41467-020-18121-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2020] [Accepted: 08/09/2020] [Indexed: 11/12/2022] Open
Abstract
The lattice dynamics and high-temperature structural transition in SnS and SnSe are investigated via inelastic neutron scattering, high-resolution Raman spectroscopy and anharmonic first-principles simulations. We uncover a spectacular, extreme softening and reconstruction of an entire manifold of low-energy acoustic and optic branches across a structural transition, reflecting strong directionality in bonding strength and anharmonicity. Further, our results solve a prior controversy by revealing the soft-mode mechanism of the phase transition that impacts thermal transport and thermoelectric efficiency. Our simulations of anharmonic phonon renormalization go beyond low-order perturbation theory and capture these striking effects, showing that the large phonon shifts directly affect the thermal conductivity by altering both the phonon scattering phase space and the group velocities. These results provide a detailed microscopic understanding of phase stability and thermal transport in technologically important materials, providing further insights on ways to control phonon propagation in thermoelectrics, photovoltaics, and other materials requiring thermal management.
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Affiliation(s)
- T Lanigan-Atkins
- Department of Mechanical Engineering and Materials Science, Duke University, Durham, NC, USA
| | - S Yang
- Department of Mechanical Engineering and Materials Science, Duke University, Durham, NC, USA
| | - J L Niedziela
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - D Bansal
- Department of Mechanical Engineering and Materials Science, Duke University, Durham, NC, USA
| | - A F May
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - A A Puretzky
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - J Y Y Lin
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - D M Pajerowski
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - T Hong
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - S Chi
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - G Ehlers
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - O Delaire
- Department of Mechanical Engineering and Materials Science, Duke University, Durham, NC, USA.
- Department of Physics, Duke University, Durham, NC, USA.
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4
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Xu J, Benton O, Islam ATMN, Guidi T, Ehlers G, Lake B. Order out of a Coulomb Phase and Higgs Transition: Frustrated Transverse Interactions of Nd_{2}Zr_{2}O_{7}. Phys Rev Lett 2020; 124:097203. [PMID: 32202891 DOI: 10.1103/physrevlett.124.097203] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Accepted: 02/12/2020] [Indexed: 06/10/2023]
Abstract
The pyrochlore material Nd_{2}Zr_{2}O_{7} with an "all-in-all-out" (AIAO) magnetic order shows novel quantum moment fragmentation with gapped flat dynamical spin ice modes. The parametrized spin Hamiltonian with a dominant frustrated ferromagnetic transverse term reveals a proximity to a U(1) spin liquid. Here we study the magnetic excitations of Nd_{2}Zr_{2}O_{7} above the ordering temperature (T_{N}) using high-energy-resolution inelastic neutron scattering. We find strong spin ice correlations at zero energy with the disappearance of gapped magnon excitations of the AIAO order. It seems that the gap to the dynamical spin ice closes above T_{N} and the system enters a quantum spin ice state competing with and suppressing the AIAO order. Classical Monte Carlo simulations, molecular dynamics, and quantum boson calculations support the existence of a Coulombic phase above T_{N}. Our findings relate the magnetic ordering of Nd_{2}Zr_{2}O_{7} with the Higgs mechanism and provide explanations for several previously reported experimental features.
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Affiliation(s)
- J Xu
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, D-14109 Berlin, Germany
- Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstraße 36, D-10623 Berlin, Germany
| | - Owen Benton
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan
| | - A T M N Islam
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, D-14109 Berlin, Germany
| | - T Guidi
- ISIS facility, Rutherford Appleton Laboratory, Didcot OX11 0QX, United Kingdom
| | - G Ehlers
- Oak Ridge National Laboratory, Oak Ridge, P.O. Box 2008, Tennessee 37831, USA
| | - B Lake
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, D-14109 Berlin, Germany
- Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstraße 36, D-10623 Berlin, Germany
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5
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Wu LS, Nikitin SE, Wang Z, Zhu W, Batista CD, Tsvelik AM, Samarakoon AM, Tennant DA, Brando M, Vasylechko L, Frontzek M, Savici AT, Sala G, Ehlers G, Christianson AD, Lumsden MD, Podlesnyak A. Tomonaga-Luttinger liquid behavior and spinon confinement in YbAlO 3. Nat Commun 2019; 10:698. [PMID: 30741939 PMCID: PMC6370837 DOI: 10.1038/s41467-019-08485-7] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [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: 06/11/2018] [Accepted: 01/14/2019] [Indexed: 11/09/2022] Open
Abstract
Low dimensional quantum magnets are interesting because of the emerging collective behavior arising from strong quantum fluctuations. The one-dimensional (1D) S = 1/2 Heisenberg antiferromagnet is a paradigmatic example, whose low-energy excitations, known as spinons, carry fractional spin S = 1/2. These fractional modes can be reconfined by the application of a staggered magnetic field. Even though considerable progress has been made in the theoretical understanding of such magnets, experimental realizations of this low-dimensional physics are relatively rare. This is particularly true for rare-earth-based magnets because of the large effective spin anisotropy induced by the combination of strong spin-orbit coupling and crystal field splitting. Here, we demonstrate that the rare-earth perovskite YbAlO3 provides a realization of a quantum spin S = 1/2 chain material exhibiting both quantum critical Tomonaga-Luttinger liquid behavior and spinon confinement-deconfinement transitions in different regions of magnetic field-temperature phase diagram.
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Affiliation(s)
- L S Wu
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA.
- Department of Physics, Southern University of Science and Technology, 518055, Shenzhen, China.
| | - S E Nikitin
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187, Dresden, Germany
- Institut für Festkörper- und Materialphysik, Technische Universität Dresden, 01069, Dresden, Germany
| | - Z Wang
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, TN, 37996, USA
| | - W Zhu
- Westlake Institute of Advanced Study, 310024, Hangzhou, P. R. China
- Theoretical Division, T-4 and CNLS, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - C D Batista
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, TN, 37996, USA
- Shull-Wollan Center, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - A M Tsvelik
- Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - A M Samarakoon
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - D A Tennant
- Shull-Wollan Center, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - M Brando
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187, Dresden, Germany
| | - L Vasylechko
- Lviv Polytechnic National University, Lviv, 79013, Ukraine
| | - M Frontzek
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - A T Savici
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - G Sala
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - G Ehlers
- Neutron Technologies Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - A D Christianson
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - M D Lumsden
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - A Podlesnyak
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA.
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6
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Sarte PM, Aczel AA, Ehlers G, Stock C, Gaulin BD, Mauws C, Stone MB, Calder S, Nagler SE, Hollett JW, Zhou HD, Gardner JS, Attfield JP, Wiebe CR. Evidence for the confinement of magnetic monopoles in quantum spin ice. J Phys Condens Matter 2017; 29:45LT01. [PMID: 29049030 DOI: 10.1088/1361-648x/aa8ec2] [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: 06/07/2023]
Abstract
Magnetic monopoles are hypothesised elementary particles connected by Dirac strings that behave like infinitely thin solenoids (Dirac 1931 Proc. R. Soc. A 133 60). Despite decades of searching, free magnetic monopoles and their Dirac strings have eluded experimental detection, although there is substantial evidence for deconfined magnetic monopole quasiparticles in spin ice materials (Castelnovo et al 2008 Nature 326 411). Here we report the detection of a hierarchy of unequally-spaced magnetic excitations via high resolution inelastic neutron spectroscopic measurements on the quantum spin ice candidate [Formula: see text] [Formula: see text] [Formula: see text]. These excitations are well-described by a simple model of monopole pairs bound by a linear potential (Coldea et al Science 327 177) with an effective tension of 0.642(8) K [Formula: see text] at 1.65 K. The success of the linear potential model suggests that these low energy magnetic excitations are direct spectroscopic evidence for the confinement of magnetic monopole quasiparticles in the quantum spin ice candidate [Formula: see text] [Formula: see text] [Formula: see text].
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Affiliation(s)
- P M Sarte
- School of Chemistry, University of Edinburgh, Edinburgh EH9 3FJ, United Kingdom. Centre for Science at Extreme Conditions, University of Edinburgh, Edinburgh EH9 3FD, United Kingdom
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7
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Ehlers G, Podlesnyak AA, Kolesnikov AI. The cold neutron chopper spectrometer at the Spallation Neutron Source-A review of the first 8 years of operation. Rev Sci Instrum 2016; 87:093902. [PMID: 27782573 DOI: 10.1063/1.4962024] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Accepted: 08/20/2016] [Indexed: 06/06/2023]
Abstract
The first eight years of operation of the Cold Neutron Chopper Spectrometer (CNCS) at the Spallation Neutron Source in Oak Ridge is being reviewed. The instrument has been part of the facility user program since 2009, and more than 250 individual user experiments have been performed to date. CNCS is an extremely powerful and versatile instrument and offers leading edge performance in terms of beam intensity, energy resolution, and flexibility to trade one for another. Experiments are being routinely performed with the sample at extreme conditions: T ≲ 0.05 K, p ≳ 2 GPa, and B = 8 T can be achieved individually or in combination. In particular, CNCS is in a position to advance the state of the art with inelastic neutron scattering under pressure, and some of the recent accomplishments in this area will be presented in more detail.
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Affiliation(s)
- G Ehlers
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - A A Podlesnyak
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - A I Kolesnikov
- Chemical and Engineering Materials Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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Wu LS, Gannon WJ, Zaliznyak IA, Tsvelik AM, Brockmann M, Caux JS, Kim MS, Qiu Y, Copley JRD, Ehlers G, Podlesnyak A, Aronson MC. Orbital-exchange and fractional quantum number excitations in an f-electron metal, Yb2Pt2Pb. Science 2016; 352:1206-10. [DOI: 10.1126/science.aaf0981] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Accepted: 04/29/2016] [Indexed: 11/02/2022]
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Ma J, Kamiya Y, Hong T, Cao HB, Ehlers G, Tian W, Batista CD, Dun ZL, Zhou HD, Matsuda M. Static and Dynamical Properties of the Spin-1/2 Equilateral Triangular-Lattice Antiferromagnet Ba_{3}CoSb_{2}O_{9}. Phys Rev Lett 2016; 116:087201. [PMID: 26967439 DOI: 10.1103/physrevlett.116.087201] [Citation(s) in RCA: 8] [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: 07/18/2015] [Indexed: 06/05/2023]
Abstract
We present single-crystal neutron scattering measurements of the spin-1/2 equilateral triangular-lattice antiferromagnet Ba_{3}CoSb_{2}O_{9}. Besides confirming that the Co^{2+} magnetic moments lie in the ab plane for zero magnetic field and then determining all the exchange parameters of the minimal quasi-2D spin Hamiltonian, we provide conclusive experimental evidence of magnon decay through observation of intrinsic line broadening. Through detailed comparisons with the linear and nonlinear spin-wave theories, we also point out that the large-S approximation, which is conventionally employed to predict magnon decay in noncollinear magnets, is inadequate to explain our experimental observation. Thus, our results call for a new theoretical framework for describing excitation spectra in low-dimensional frustrated magnets under strong quantum effects.
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Affiliation(s)
- J Ma
- Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Y Kamiya
- iTHES Research Group and Condensed Matter Theory Laboratory, RIKEN, Wako, Saitama 351-0198, Japan
| | - Tao Hong
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - H B Cao
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - G Ehlers
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - W Tian
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - C D Batista
- Theoretical Division, T-4 and CNLS, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Z L Dun
- Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA
| | - H D Zhou
- Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310-3706, USA
| | - M Matsuda
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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10
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Ehlers G, Podlesnyak AA, Frontzek MD, Pushkarev AV, Shiryaev SV, Barilo S. Damped spin waves in the intermediate ordered phases in Ni3V2O8. J Phys Condens Matter 2015; 27:256003. [PMID: 26058062 DOI: 10.1088/0953-8984/27/25/256003] [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: 06/04/2023]
Abstract
Spin dynamics in the intermediate ordered phases (between 4 and 9 K) in Ni3V2O8 have been studied with inelastic neutron scattering. It is found that the spin waves are very diffuse, indicative of short lived correlations and the coexistence of paramagnetic moments with the long-range ordered state.
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Affiliation(s)
- G Ehlers
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6475, USA.
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12
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Wang CH, Poudel L, Taylor AE, Lawrence JM, Christianson AD, Chang S, Rodriguez-Rivera JA, Lynn JW, Podlesnyak AA, Ehlers G, Baumbach RE, Bauer ED, Gofryk K, Ronning F, McClellan KJ, Thompson JD. Quantum critical fluctuations in the heavy fermion compound Ce(Ni0.935Pd0.065)₂Ge₂. J Phys Condens Matter 2015; 27:015602. [PMID: 25469766 DOI: 10.1088/0953-8984/27/1/015602] [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: 06/04/2023]
Abstract
Electric resistivity, specific heat, magnetic susceptibility, and inelastic neutron scattering experiments were performed on a single crystal of the heavy fermion compound Ce(Ni0.935Pd0.065)2Ge2 in order to study the spin fluctuations near an antiferromagnetic (AF) quantum critical point (QCP). The resistivity and the specific heat coefficient for T ⩽ 1 K exhibit the power law behavior expected for a 3D itinerant AF QCP (ρ(T) ∼ T(3/2) and γ(T) ∼ γ0 - bT(1/2)). However, for 2 ⩽ T ⩽ 10 K, the susceptibility and specific heat vary as log T and the resistivity varies linearly with temperature. Furthermore, despite the fact that the resistivity and specific heat exhibit the non-Fermi liquid behavior expected at a QCP, the correlation length, correlation time, and staggered susceptibility of the spin fluctuations remain finite at low temperature. We suggest that these deviations from the divergent behavior expected for a QCP may result from alloy disorder.
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Affiliation(s)
- C H Wang
- Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA. University of California, Irvine, CA 92697, USA
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13
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Perticaroli S, Russo D, Paolantoni M, Gonzalez MA, Sassi P, Nickels JD, Ehlers G, Comez L, Pellegrini E, Fioretto D, Morresi A. Painting biological low-frequency vibrational modes from small peptides to proteins. Phys Chem Chem Phys 2015; 17:11423-31. [DOI: 10.1039/c4cp05388e] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
We use experiments and simulation to investigate the validity of different model systems used to study the low-frequency vibrations of proteins.
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Affiliation(s)
- S. Perticaroli
- Joint Institute for Neutron Sciences
- Oak Ridge National Laboratory
- Oak Ridge
- USA
- Chemical and Materials Sciences Division
| | - D. Russo
- CNR-IOM
- Italy c/o Institut Laue Langevin
- France
- Institut Lumière Matière
- Université de Lyon 1
| | - M. Paolantoni
- Dipartimento di Chimica
- Biologia e Biotecnologie
- Università di Perugia
- I-06123 Perugia
- Italy
| | | | - P. Sassi
- Dipartimento di Chimica
- Biologia e Biotecnologie
- Università di Perugia
- I-06123 Perugia
- Italy
| | - J. D. Nickels
- Joint Institute for Neutron Sciences
- Oak Ridge National Laboratory
- Oak Ridge
- USA
- Department of Chemistry
| | - G. Ehlers
- Quantum Condensed Matter Division
- Oak Ridge National Laboratory
- Oak Ridge
- USA
| | - L. Comez
- IOM-CNR c/o Dipartimento di Fisica e Geologia
- Università di Perugia
- I-06123 Perugia
- Italy
- Dipartimento di Fisica e Geologia
| | | | - D. Fioretto
- Dipartimento di Fisica e Geologia
- Università di Perugia
- I-06123 Perugia
- Italy
- Centro di Eccellenza sui Materiali Innovativi Nanostrutturati (CEMIN)
| | - A. Morresi
- Dipartimento di Chimica
- Biologia e Biotecnologie
- Università di Perugia
- I-06123 Perugia
- Italy
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14
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Das P, Lin SZ, Ghimire NJ, Huang K, Ronning F, Bauer ED, Thompson JD, Batista CD, Ehlers G, Janoschek M. Magnitude of the magnetic exchange interaction in the heavy-fermion antiferromagnet CeRhIn₅. Phys Rev Lett 2014; 113:246403. [PMID: 25541784 DOI: 10.1103/physrevlett.113.246403] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Indexed: 06/04/2023]
Abstract
We have used high-resolution neutron spectroscopy experiments to determine the complete spin wave spectrum of the heavy-fermion antiferromagnet CeRhIn₅. The spin wave dispersion can be quantitatively reproduced with a simple frustrated J₁-J₂ model that also naturally explains the magnetic spin-spiral ground state of CeRhIn₅ and yields a dominant in-plane nearest-neighbor magnetic exchange constant J₀=0.74(3) meV. Our results pave the way to a quantitative understanding of the rich low-temperature phase diagram of the prominent CeTIn₅ (T=Co, Rh, Ir) class of heavy-fermion materials.
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Affiliation(s)
- Pinaki Das
- Condensed Matter and Magnet Science, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - S-Z Lin
- T-4, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - N J Ghimire
- Condensed Matter and Magnet Science, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - K Huang
- Condensed Matter and Magnet Science, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA and Department of Physics, University of California, San Diego, La Jolla, California 92093, USA
| | - F Ronning
- Condensed Matter and Magnet Science, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - E D Bauer
- Condensed Matter and Magnet Science, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - J D Thompson
- Condensed Matter and Magnet Science, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - C D Batista
- T-4, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - G Ehlers
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6475, USA
| | - M Janoschek
- Condensed Matter and Magnet Science, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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15
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Clark L, Nilsen GJ, Kermarrec E, Ehlers G, Knight KS, Harrison A, Attfield JP, Gaulin BD. From spin glass to quantum spin liquid ground states in molybdate pyrochlores. Phys Rev Lett 2014; 113:117201. [PMID: 25260001 DOI: 10.1103/physrevlett.113.117201] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2014] [Indexed: 06/03/2023]
Abstract
We present new magnetic heat capacity and neutron scattering results for two magnetically frustrated molybdate pyrochlores: S=1 oxide Lu_{2}Mo_{2}O_{7} and S=1/2 oxynitride Lu_{2}Mo_{2}O_{5}N_{2}. Lu_{2}Mo_{2}O_{7} undergoes a transition to an unconventional spin glass ground state at T_{f}∼16 K. However, the preparation of the corresponding oxynitride tunes the nature of the ground state from spin glass to quantum spin liquid. The comparison of the static and dynamic spin correlations within the oxide and oxynitride phases presented here reveals the crucial role played by quantum fluctuations in the selection of a ground state. Furthermore, we estimate an upper limit for a gap in the spin excitation spectrum of the quantum spin liquid state of the oxynitride of Δ∼0.05 meV or Δ/|θ|∼0.004, in units of its antiferromagnetic Weiss constant θ∼-121 K.
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Affiliation(s)
- L Clark
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4M1, Canada
| | - G J Nilsen
- Institute Laue-Langevin, 6 Rue Jules Horowitz, 38042 Grenoble, France
| | - E Kermarrec
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4M1, Canada
| | - G Ehlers
- Neutron Scattering Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - K S Knight
- ISIS Facility, Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0QX, United Kingdom
| | - A Harrison
- CSEC and School of Chemistry, University of Edinburgh, Mayfield Road, Edinburgh EH9 3JZ, United Kingdom and Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0QX, United Kingdom
| | - J P Attfield
- CSEC and School of Chemistry, University of Edinburgh, Mayfield Road, Edinburgh EH9 3JZ, United Kingdom
| | - B D Gaulin
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4M1, Canada and Brockhouse Institute for Materials Research, Hamilton, Ontario L8S 4M1, Canada and Canadian Institute for Advanced Research, 180 Dundas Street West, Toronto, Ontario M5G 1Z8, Canada
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Cherkashyna N, Kanaki K, Kittelmann T, Filges U, Deen P, Herwig K, Ehlers G, Greene G, Carpenter J, Connatser R, Hall-Wilton R, Bentley PM. High energy particle background at neutron spallation sources and possible solutions. ACTA ACUST UNITED AC 2014. [DOI: 10.1088/1742-6596/528/1/012013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Li CW, Hellman O, Ma J, May AF, Cao HB, Chen X, Christianson AD, Ehlers G, Singh DJ, Sales BC, Delaire O. Phonon self-energy and origin of anomalous neutron scattering spectra in SnTe and PbTe thermoelectrics. Phys Rev Lett 2014; 112:175501. [PMID: 24836255 DOI: 10.1103/physrevlett.112.175501] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Indexed: 05/02/2023]
Abstract
The anharmonic lattice dynamics of rock-salt thermoelectric compounds SnTe and PbTe are investigated with inelastic neutron scattering (INS) and first-principles calculations. The experiments show that, surprisingly, although SnTe is closer to the ferroelectric instability, phonon spectra in PbTe exhibit a more anharmonic character. This behavior is reproduced in first-principles calculations of the temperature-dependent phonon self-energy. Our simulations reveal how the nesting of phonon dispersions induces prominent features in the self-energy, which account for the measured INS spectra and their temperature dependence. We establish that the phase space for three-phonon scattering processes, combined with the proximity to the lattice instability, is the mechanism determining the complex spectrum of the transverse-optic ferroelectric mode.
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Affiliation(s)
- C W Li
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - O Hellman
- Department of Physics, Chemistry and Biology, Linköping University, Linköping SE-581 83, Sweden
| | - J Ma
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - A F May
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - H B Cao
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - X Chen
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - A D Christianson
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - G Ehlers
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - D J Singh
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - B C Sales
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - O Delaire
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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18
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Stone MB, Niedziela JL, Abernathy DL, DeBeer-Schmitt L, Ehlers G, Garlea O, Granroth GE, Graves-Brook M, Kolesnikov AI, Podlesnyak A, Winn B. A comparison of four direct geometry time-of-flight spectrometers at the Spallation Neutron Source. Rev Sci Instrum 2014; 85:045113. [PMID: 24784665 DOI: 10.1063/1.4870050] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The Spallation Neutron Source at Oak Ridge National Laboratory now hosts four direct geometry time-of-flight chopper spectrometers. These instruments cover a range of wave-vector and energy transfer space with varying degrees of neutron flux and resolution. The regions of reciprocal and energy space available to measure at these instruments are not exclusive and overlap significantly. We present a direct comparison of the capabilities of this instrumentation, conducted by data mining the instrument usage histories, and specific scanning regimes. In addition, one of the common science missions for these instruments is the study of magnetic excitations in condensed matter systems. We have measured the powder averaged spin wave spectra in one particular sample using each of these instruments, and use these data in our comparisons.
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Affiliation(s)
- M B Stone
- Quantum Condensed Matter Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - J L Niedziela
- Instrument and Source Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - D L Abernathy
- Quantum Condensed Matter Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - L DeBeer-Schmitt
- Instrument and Source Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - G Ehlers
- Quantum Condensed Matter Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - O Garlea
- Quantum Condensed Matter Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - G E Granroth
- Neutron Data Analysis and Visualization Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - M Graves-Brook
- Instrument and Source Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - A I Kolesnikov
- Chemical and Engineering Materials Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - A Podlesnyak
- Quantum Condensed Matter Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - B Winn
- Quantum Condensed Matter Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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Ehlers G, Podlesnyak AA, Frontzek M, Freitas RS, Ghivelder L, Gardner JS, Shiryaev SV, Barilo S. A detailed study of the magnetic phase transition in CuCrO2. J Phys Condens Matter 2013; 25:496009. [PMID: 24214902 DOI: 10.1088/0953-8984/25/49/496009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The phase transition in CuCrO2 to an ordered magnetic state is studied with bulk measurements and elastic and inelastic neutron scattering techniques. The reported onset of spontaneous electric polarization at T = 23.5 K coincides with the appearance, on cooling, of elastic magnetic scattering. At higher temperatures long range magnetic correlations gradually develop but they are dynamic. The ground state is characterized by three-dimensional long range magnetic ordering but along the c direction the correlation length remains limited to ∼200 Å.
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Affiliation(s)
- G Ehlers
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831-6475, USA
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22
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Ehlers G, Stewart JR, Wildes AR, Deen PP, Andersen KH. Generalization of the classical xyz-polarization analysis technique to out-of-plane and inelastic scattering. Rev Sci Instrum 2013; 84:093901. [PMID: 24089835 DOI: 10.1063/1.4819739] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The technique of longitudinal ("xyz") polarization analysis has been used successfully for many years to study disordered magnetic materials in thermal and cold neutron diffraction experiments. The technique allows the simultaneous and unambiguous separation of the nuclear, magnetic, and nuclear spin-incoherent contributions to the scattering. The technical advances seen in recent years, such as the availability of polarized (3)He analyzer cells to cover a large detector solid angle, the ability to detect out-of-plane scattering in a multi-detector, and a significant increase of the usable beam divergence, call for a generalization of the method. A general treatment of the formalism for carrying out neutron polarization analysis will be given in this paper, which describes a possible method of usage at a future, modern diffractometer or inelastic spectrometer with large area multi-detector coverage.
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Affiliation(s)
- G Ehlers
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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Ma J, Delaire O, May AF, Carlton CE, McGuire MA, VanBebber LH, Abernathy DL, Ehlers G, Hong T, Huq A, Tian W, Keppens VM, Shao-Horn Y, Sales BC. Glass-like phonon scattering from a spontaneous nanostructure in AgSbTe2. Nat Nanotechnol 2013; 8:445-451. [PMID: 23728075 DOI: 10.1038/nnano.2013.95] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2012] [Accepted: 04/25/2013] [Indexed: 06/02/2023]
Abstract
Materials with very low thermal conductivity are of great interest for both thermoelectric and optical phase-change applications. Synthetic nanostructuring is most promising for suppressing thermal conductivity through phonon scattering, but challenges remain in producing bulk samples. In crystalline AgSbTe2 we show that a spontaneously forming nanostructure leads to a suppression of thermal conductivity to a glass-like level. Our mapping of the phonon mean free paths provides a novel bottom-up microscopic account of thermal conductivity and also reveals intrinsic anisotropies associated with the nanostructure. Ground-state degeneracy in AgSbTe2 leads to the natural formation of nanoscale domains with different orderings on the cation sublattice, and correlated atomic displacements, which efficiently scatter phonons. This mechanism is general and suggests a new avenue for the nanoscale engineering of materials to achieve low thermal conductivities for efficient thermoelectric converters and phase-change memory devices.
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Affiliation(s)
- J Ma
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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24
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Ehlers G, Huq A, Diallo SO, Adriano C, Rule KC, Cornelius AL, Fouquet P, Pagliuso PG, Gardner JS. Low energy spin dynamics in the spin ice Ho2Sn2O7. J Phys Condens Matter 2012; 24:076005. [PMID: 22293128 DOI: 10.1088/0953-8984/24/7/076005] [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: 05/31/2023]
Abstract
The magnetic properties of Ho(2)Sn(2)O(7) have been investigated and compared to other spin ice compounds. Although the lattice has expanded by 3% relative to the better studied Ho(2)Ti(2)O(7) spin ice, no significant changes were observed in the high temperature properties, T is more or approximately equal to 20 K. As the temperature is lowered and correlations develop, Ho(2)Sn(2)O(7) enters its quantum phase at a slightly higher temperature than Ho(2)Ti(2)O(7) and is more antiferromagnetic in character. Below 80 K a weak inelastic mode associated with the holmium nuclear spin system has been measured. The hyperfine field at the holmium nucleus was found to be ≈700 T.
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Affiliation(s)
- G Ehlers
- Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6475, USA.
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25
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Frontzek M, Ehlers G, Podlesnyak A, Cao H, Matsuda M, Zaharko O, Aliouane N, Barilo S, Shiryaev SV. Magnetic structure of CuCrO₂: a single crystal neutron diffraction study. J Phys Condens Matter 2012; 24:016004. [PMID: 22155990 DOI: 10.1088/0953-8984/24/1/016004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
This paper presents results of a recent study of multiferroic CuCrO(2) by means of single crystal neutron diffraction. This system has two close magnetic phase transitions at T(N) = 24.2 K and T(mf) = 23.6 K. The low temperature magnetic structure below T(mf) is unambiguously determined to be a fully three-dimensional proper screw. Between T(N) and T(mf) antiferromagnetic order is found that is essentially two-dimensional. In this narrow temperature range, magnetic near neighbor correlations are still long range in the (H,K) plane, whereas nearest neighbors along the L direction are uncorrelated. Thus, the multiferroic state is realized only in the low temperature three-dimensional state and not in the two-dimensional state.
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Affiliation(s)
- M Frontzek
- Neutron Scattering Science Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
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26
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Stone MB, Podlesnyak A, Ehlers G, Huq A, Samulon EC, Shapiro MC, Fisher IR. Persistence of magnons in a site-diluted dimerized frustrated antiferromagnet. J Phys Condens Matter 2011; 23:416003. [PMID: 21952109 DOI: 10.1088/0953-8984/23/41/416003] [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: 05/31/2023]
Abstract
We present inelastic neutron scattering and thermodynamic measurements characterizing the magnetic excitations in a disordered spin-liquid antiferromagnet with non-magnetic substitution. The parent compound Ba(3)Mn(2)O(8) is a dimerized, quasi-two-dimensional geometrically frustrated quantum disordered antiferromagnet. We substitute this compound with non-magnetic V(5+) for the S=1 Mn(5+) ions, Ba(3)(Mn(1-x)V (x))(2)O(8), and find that the singlet-triplet excitations which dominate the spectrum of the parent compound persist for the full range of substitution examined, up to x=0.3. We also observe additional low-energy magnetic fluctuations which are enhanced at the greatest substitution values.
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Affiliation(s)
- M B Stone
- Neutron Scattering Science Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
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Ehlers G, Podlesnyak AA, Niedziela JL, Iverson EB, Sokol PE. The new cold neutron chopper spectrometer at the Spallation Neutron Source: design and performance. Rev Sci Instrum 2011; 82:085108. [PMID: 21895276 DOI: 10.1063/1.3626935] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.0] [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
The design and performance of the new cold neutron chopper spectrometer (CNCS) at the Spallation Neutron Source in Oak Ridge are described. CNCS is a direct-geometry inelastic time-of-flight spectrometer, designed essentially to cover the same energy and momentum transfer ranges as IN5 at ILL, LET at ISIS, DCS at NIST, TOFTOF at FRM-II, AMATERAS at J-PARC, PHAROS at LANSCE, and NEAT at HZB, at similar energy resolution. Measured values of key figures such as neutron flux at sample position and energy resolution are compared between measurements and ray tracing Monte Carlo simulations, and good agreement (better than 20% of absolute numbers) has been achieved. The instrument performs very well in the cold and thermal neutron energy ranges, and promises to become a workhorse for the neutron scattering community for quasielastic and inelastic scattering experiments.
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Affiliation(s)
- G Ehlers
- Neutron Scattering Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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Delaire O, Ma J, Marty K, May AF, McGuire MA, Du MH, Singh DJ, Podlesnyak A, Ehlers G, Lumsden MD, Sales BC. Giant anharmonic phonon scattering in PbTe. Nat Mater 2011; 10:614-9. [PMID: 21642983 DOI: 10.1038/nmat3035] [Citation(s) in RCA: 174] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2011] [Accepted: 04/22/2011] [Indexed: 05/24/2023]
Abstract
Understanding the microscopic processes affecting the bulk thermal conductivity is crucial to develop more efficient thermoelectric materials. PbTe is currently one of the leading thermoelectric materials, largely thanks to its low thermal conductivity. However, the origin of this low thermal conductivity in a simple rocksalt structure has so far been elusive. Using a combination of inelastic neutron scattering measurements and first-principles computations of the phonons, we identify a strong anharmonic coupling between the ferroelectric transverse optic mode and the longitudinal acoustic modes in PbTe. This interaction extends over a large portion of reciprocal space, and directly affects the heat-carrying longitudinal acoustic phonons. The longitudinal acoustic-transverse optic anharmonic coupling is likely to play a central role in explaining the low thermal conductivity of PbTe. The present results provide a microscopic picture of why many good thermoelectric materials are found near a lattice instability of the ferroelectric type.
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Affiliation(s)
- O Delaire
- Neutron Scattering Science Division, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, Tennessee 37831, USA.
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Gardner JS, Ehlers G, Fouquet P, Farago B, Stewart JR. Slow and static spin correlations in Dy(2 + x)Ti(2 - x)O(7 - δ). J Phys Condens Matter 2011; 23:164220. [PMID: 21471620 DOI: 10.1088/0953-8984/23/16/164220] [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: 05/30/2023]
Abstract
The static and dynamic spin correlations in the spin ices Dy(2.3)Ti(1.7)O(6.85) and Dy(2)Ti(2)O(7) have been studied in polarized neutron diffraction and neutron spin echo experiments. The measurements reveal that, below 100 mK, the magnetic scattering broadens and shifts to higher |Q| upon stuffing the pyrochlore lattice with additional Dy(3+) ions. These observations can be related, by means of reverse Monte Carlo simulation, to the modified distribution of near-neighbour distances and an overall more antiferromagnetic character of the near-neighbour couplings. The dynamic measurements show that the spin correlations are slower in the stuffed system. These results will be discussed and compared to the holmium analogues.
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Affiliation(s)
- J S Gardner
- Physics Department, Indiana University, Bloomington, IN 47408, USA.
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Rule KC, Ehlers G, Gardner JS, Qiu Y, Moskvin E, Kiefer K, Gerischer S. Neutron scattering investigations of the partially ordered pyrochlore Tb(2)Sn(2)O(7). J Phys Condens Matter 2009; 21:486005. [PMID: 21832537 DOI: 10.1088/0953-8984/21/48/486005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Neutron scattering measurements have been performed on polycrystalline Tb(2)Sn(2)O(7) at temperatures above and below that of the phase transition, T(N) = 0.87 K, to investigate further the spin dynamics in the magnetically ordered state. In particular, new neutron spin echo results are presented showing a dependence on Q in the dynamics. We show evidence of the coexistence of static ferromagnetism and dynamically fluctuating spins down to 30 mK and we make a comparison of this partially ordered system to the spin liquid Tb(2)Ti(2)O(7).
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Affiliation(s)
- K C Rule
- Helmholtz Zentrum Berlin, 14109 Berlin, Germany
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Abstract
The magnetic pyrochlore Er(2)Ru(2)O(7) has been studied with neutron scattering and susceptibility measurements down to a base temperature of 270 mK. For the low temperature phase in which the Er sublattice orders, new magnetic Bragg peaks are reported which can be indexed with integer (hkl) for a face centered cubic cell. Inelastic measurements reveal a wealth of crystal field levels of the Er ion and a copious amount of magnetic scattering below 15 meV. The three lowest groups of crystal field levels are at 6.7, 9.1 and 18.5 meV.
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Affiliation(s)
- J S Gardner
- Department of Physics, Indiana University, Bloomington, IN 47408, USA. NCNR, NIST, Gaithersburg, MD 20899-6102, USA
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Huth K, Ehlers G, Knoth W, Kunze K, Löffler H, Mähr G, Petzoldt D. Lichen myxoedematosus bei Makroglobulinämie Waldenström mit Polyneuropathie und Carpaltunnel-Syndrom. Dtsch Med Wochenschr 2009. [DOI: 10.1055/s-0028-1107317] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Ehlers G, Mamontov E, Zamponi M, Kam KC, Gardner JS. Direct observation of a nuclear spin excitation in Ho2Ti2O7. Phys Rev Lett 2009; 102:016405. [PMID: 19257221 DOI: 10.1103/physrevlett.102.016405] [Citation(s) in RCA: 3] [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: 10/17/2008] [Indexed: 05/27/2023]
Abstract
A single nondispersive excitation is observed by means of neutron backscattering, at E_{0}=26.3 microeV in the spin ice Ho2Ti2O7 but not in the isotopically enriched 162Dy2Ti2O7 analogue. The intensity of this excitation is rather small, less, similar0.2% of the elastic intensity. It is clearly observed below 80 K but resolution limited only below approximately 65 K. The application of a magnetic field up to micro_{0}H=4.5 T, at 1.6 K, has no measurable effect on the energy or intensity. This nuclear excitation is believed to perturb the electronic, Ising spin system resulting in the persistent spin dynamics observed in spin ice compounds.
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Affiliation(s)
- G Ehlers
- Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6475, USA
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Bermejo FJ, Cabrillo C, Bychkov E, Fouquet P, Ehlers G, Häussler W, Price DL, Saboungi ML. Tracking the effects of rigidity percolation down to the liquid state: relaxational dynamics of binary chalcogen melts. Phys Rev Lett 2008; 100:245902. [PMID: 18643601 DOI: 10.1103/physrevlett.100.245902] [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: 01/29/2008] [Indexed: 05/26/2023]
Abstract
The stochastic dynamics of binary liquids with formula AxB1-x, x=0-0.4 is investigated by neutron spin-echo spectroscopy. These compositions comprise samples of varying chemical connectivity, ranging from twofold-coordinated liquid Se to higher average coordinated As2S3. The parameters giving the temperature dependence of the relaxation patterns show a quasilinear dependence on the average coordination number. The results thus extend the validity of the rigidity concept into the normal liquid state and emphasize the role played by the fine details of atomic bonding on the dynamics at 10 ps-1 ns scales.
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Affiliation(s)
- F J Bermejo
- Instituto de Estructura de la Materia, CSIC, and Department Electricidad y Electrónica-Unidad Asociada CSIC, Facultad de Ciencia y Tecnología, Universidad del País Vasco/EHU, P. Box 644, E-48080-Bilbao, Spain
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Ehlers G, Mamontov E, Zamponi M, Faraone A, Qiu Y, Cornelius AL, Booth CH, Kam KC, Toquin RL, Cheetham AK, Gardner JS. Frustrated spin correlations in diluted spin ice Ho(2-x)La(x)Ti(2)O(7). J Phys Condens Matter 2008; 20:235206. [PMID: 21694297 DOI: 10.1088/0953-8984/20/23/235206] [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] [Indexed: 05/30/2023]
Abstract
We have studied the evolution of the structural properties as well as the static and dynamic spin correlations of spin ice Ho(2)Ti(2)O(7), where Ho was partially replaced by non-magnetic La. The crystal structure of diluted samples Ho(2-x)La(x)Ti(2)O(7) was characterized by x-ray and neutron diffraction and by Ho L(III)-edge and Ti K-edge extended x-ray absorption fine structure (EXAFS) measurements. It is found that the pyrochlore structure remains intact until about x = 0.3, but a systematic increase in local disorder with increasing La concentration is observed in the EXAFS data, especially from the Ti K edge. Quasi-elastic neutron scattering and ac susceptibility measurements show that, in x≤0.4 samples at temperatures above macroscopic freezing, the spin-spin correlations are short ranged and dynamic in nature. The main difference with pure spin ice in the dynamics is the appearance of a second, faster, relaxation process.
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Affiliation(s)
- G Ehlers
- Spallation Neutron Source, Oak Ridge National Laboratory, Building 8600, Oak Ridge, TN 37831-6475, USA
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36
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Mutka H, Ehlers G, Payen C, Bono D, Stewart JR, Fouquet P, Mendels P, Mevellec JY, Blanchard N, Collin G. Neutron spin-echo investigation of slow spin dynamics in kagomé-bilayer frustrated magnets as evidence for phonon assisted relaxation in SrCr9xGa12-9xO19. Phys Rev Lett 2006; 97:047203. [PMID: 16907610 DOI: 10.1103/physrevlett.97.047203] [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: 03/20/2006] [Indexed: 05/11/2023]
Abstract
A neutron spin-echo investigation of the low temperature spin dynamics in two well-characterized kagomé bilayer compounds SrCr9xGa12-9xO19 (x=0.95, SCGO) and Ba2Sn2ZnCr7xGa10-7xO22 (x=0.97, BSZCGO) reveals two novel features. One is the slowing down of the relaxation rate without critical behavior at Tg, where a macroscopic spin-glass-like freezing occurs. The second is, in SCGO at 4 K (approximately Tg)<T<7 K, the relaxation rate activation energy Ea=7+/-0.4 meV, equal to the energy of a phonon mode, pointing out the role of spin-lattice coupling.
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Affiliation(s)
- H Mutka
- Institut Laue-Langevin, Boîte Postale 156X, F-38042 Grenoble Cedex 9, France.
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Keren A, Gardner JS, Ehlers G, Fukaya A, Segal E, Uemura YJ. Dynamic properties of a diluted pyrochlore cooperative paramagnet (Tb(p)Y(1-p))2Ti2O7. Phys Rev Lett 2004; 92:107204. [PMID: 15089239 DOI: 10.1103/physrevlett.92.107204] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2003] [Indexed: 05/24/2023]
Abstract
Investigations of the spin dynamics of the geometrically frustrated pyrochlore (Tb(p)Y(1-p))2Ti2O7, using muon spin relaxation and neutron spin echo, as a function of magnetic coverage p, have been carried out. Our major finding is that paramagnetic fluctuations prevail as T-->0 for all values of p, and that they are sensitive to dilution, indicating a cooperative spin motion. However, the percolation threshold pc is not a critical point for the fluctuations. We also find that the low temperature spectral density has a 1/f behavior, and that dilution slows down the spin fluctuations.
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Affiliation(s)
- A Keren
- Department of Physics, Technion-Israel Institute of Technology, Haifa 32000, Israel
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Heffner RH, Sonier JE, MacLaughlin DE, Nieuwenhuys GJ, Ehlers G, Mezei F, Cheong SW, Gardner JS, Röder H. Observation of two time scales in the ferromagnetic manganite La1-xCaxMnO3, x approximately 0.3. Phys Rev Lett 2000; 85:3285-3288. [PMID: 11019322 DOI: 10.1103/physrevlett.85.3285] [Citation(s) in RCA: 3] [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: 08/23/1999] [Indexed: 05/23/2023]
Abstract
We report new zero-field muon spin relaxation and neutron spin echo measurements in ferromagnetic (FM) (La,Ca)MnO3 which suggest at least two spatially separated regions possessing very different Mn-ion spin dynamics. One region displays diffusive relaxation, "critical slowing down" near T(C) and an increasing volume fraction below T(C), suggesting overdamped FM spin waves below T(C). The second region possesses more slowly fluctuating spins, a linewidth independent of q, and a decreasing volume fraction below T(C). The estimated length scale for the inhomogeneity is <or=30 A.
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Affiliation(s)
- R H Heffner
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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Plowman SA, Dustman K, Walicek H, Corless C, Ehlers G. The effects of ENDUROX on the physiological responses to stair-stepping exercise. Res Q Exerc Sport 1999; 70:385-388. [PMID: 10797896 DOI: 10.1080/02701367.1999.10608058] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Affiliation(s)
- S A Plowman
- Department of Kinesiology and Physical Education, Northern Illinois University, USA.
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Ehlers G, Mezei F. Laue diffractometer at a long pulse spallation source. GNER 1997. [DOI: 10.1080/10238169708200106] [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: 10/23/2022]
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Bratzke B, Orfanos CE, Stavermann T, Ehlers G. [Chronic erosive, therapy-resistant perianal herpes (type II) with herpes proctitis in AIDS]. Hautarzt 1991; 42:96-100. [PMID: 1828066] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
In an AIDS patient who had repeated successful treatment with acyclovir in his history, erosive herpes perianalis with herpes proctitis appeared, which persisted over several weeks. High-dose intravenous administration on of acyclovir (500-750 mg, 3 x daily, over 7 weeks) did not reveal any beneficial effects: However, almost complete clearing of the lesions occurred within 3 weeks of intravenous administration of Foscarnet (50 mg/kg body wt., 3 x daily). No relapse was seen in a follow-up period of 4 months. HSV type II was isolated by culture from the erosive lesions before treatment, but no virus was found 1 week after application of Foscarnet. The unusual chronic refractory course of a severe HSV type II infection in AIDS suggests the presence of an acyclovir-resistant HSV strain in this case. This is the first observation indicating acyclovir-resistance in the Federal Republic of Germany and a warning against the unlimited use of acyclovir in AIDS patients. Foscarnet may be beneficial in some of these cases.
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Affiliation(s)
- B Bratzke
- Universitäts-Hautklinik und Poliklinik, Klinikum Steglitz, Freien Universität Berlin
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Schaart FM, Bratzke B, Ruszczak Z, Stadler R, Ehlers G, Orfanos CE. Long-term therapy of HIV-associated Kaposi's sarcoma with recombinant interferon alpha-2a. Br J Dermatol 1991; 124:62-8. [PMID: 1825174 DOI: 10.1111/j.1365-2133.1991.tb03283.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Five young male patients with HIV-associated Kaposi's sarcoma (KS) were treated with recombinant interferon alpha 2a (rIFN-alpha-2a) over a period of 2-2.5 years. An IFN dose of 18 x 10(6) IU was given subcutaneously every day during the first 3 months of treatment and then on alternate days. Additional treatment with radiotherapy and laser therapy was given and, in some cases, isolated skin nodules were excised. Within 7 months of initiation of therapy one patient had a complete remission of his tumours, however, tumour progression recurred after the patient discontinued treatment. In another patient the tumour cleared within 9 months of rIFN therapy, and after 52 months he is still free of KS. The condition of a third patient tended to become stabilized during the first 6 months of therapy, but after 60 months there has been a slow progression. The fourth and fifth patients died 25 and 28 months, respectively, after the histological diagnosis of KS and the initiation of treatment. While on therapy with rIFN-alpha-2a, no life-threatening opportunistic infections occurred. The side-effects were mostly well tolerated, and no severe changes in haematological parameters were caused by the therapy.
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Affiliation(s)
- F M Schaart
- Department of Dermatology, University Medical Center Steglitz, Free University of Berlin, Germany
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Bratzke B, Eichhorn R, Höffken G, Bratzke C, Stadler R, Ehlers G, Orfanos CE. [Acute primary phase as an indicator of HIV-1 infection. The general symptoms and polymorphic exanthema with mouth mucosal involvement 2 to 6 weeks before seroconversion]. Dtsch Med Wochenschr 1988; 113:1312-6. [PMID: 3165756 DOI: 10.1055/s-2008-1067812] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The initial symptoms of an HIV-1 infection were observed in four patients. The following were characteristic for the acute primary phase: (a) initial maculopapular exanthema, especially of the trunk, with occasional transition into a papulovesical appearance; (b) involvement of the oral mucosa, often of aphthous character; and (c) general malaise with fever and lymphadenopathy. The observed cutaneous changes had, on one hand, features of a Coxsackie or mononucleosis exanthema, on the other of secondary syphilis. In three patients seroconversion occurred within 2-6 weeks, the fourth failed to return for follow-up. The listed acute primary symptoms can be used as the earliest indicators of an HIV-1 infection having occurred.
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Affiliation(s)
- B Bratzke
- Universitäts-Hautklinik und Poliklinik, Klinikum Steglitz, Freie Universität Berlin
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Mayerhausen W, Ehlers G. [Congenital telangiectatic erythema (Bloom syndrome)]. Hautarzt 1988; 39:363-7. [PMID: 3042705] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
"Congenital telangiectatic erythema" (Bloom's syndrome) is very rare; it is linked to a group of hereditary diseases and a common feature is cellular hypersensitivity to a variety of physical or chemical agents. The mode of transmission is autosomal-recessive. Characteristic criteria for Bloom syndrome are: consanguinity of the parents; androtropia; low birth weight, short stature (proportional); and persistent telangiectatic erythema in sun-exposed areas, sometimes with blistering. The syndrome is also associated with a facultative lack of antibodies. Of great importance is the high leukaemia morbidity among individuals with this syndrome; chromosomal aberrations and breakages play a significant role. Histological changes comprise an increase in dilated vessels in the upper dermis and damage and loss of elastic fibers. We give a review of Bloom's syndrome and present a case report.
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Affiliation(s)
- W Mayerhausen
- Dermatologische Klinik und Poliklinik, Technische Universität München
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Bratzke B, Stadler R, Eichhorn R, Ehlers G, Orfanos CE. [Disseminated mucocutaneous Kaposi sarcoma in AIDS. Clinical and therapeutic experiences in 13 patients]. Hautarzt 1987; 38:286-94. [PMID: 3610636] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Since 1980 a new epidemic form of disseminated mucocutaneous Kaposi's sarcoma (KS) with a progressive clinical course has been observed in populations at risk. Since 1982, 13 cases of AIDS-associated KS have been seen in our department; all of them were in young homosexual males with circulating HIV antibodies and a reduction in the ratio of T-helper to T-suppressor lymphocytes (0.05-1.3). Following systemic treatment with recombinant alpha A-interferon (rIFN-alpha A) over a period of 6 months (18 million IU/day for 3 months; later 18 million IU/3 X weekly) together with other concomitant measures (superficial X-ray radiation, argon laser radiation, surgical excision of isolated lesions) we registered complete remission of the remaining lesions in 2 cases, progression of the disease in 4 cases, and at least temporary stabilization of the disease in 7 cases. In 4 patients opportunistic infections occurred during rIFN treatment: Pneumocystis carinii pneumonia (PCP) with lethal outcome in 2 cases, atypical mycobacteriosis in 2 cases, and Legionella pneumoniae infection in 1 case. Two additional deaths were registered due to PCP appearing during the post-treatment period. Life-threatening virus infections were not observed during rIFN treatment. Out of 9 patients receiving prophylactic trimethoprim/sulfamethoxazole medication, only 1 developed allergic exanthema as a result of this drug combination. Occasionally, rIFN-induced leukopenia was seen and pronounced thrombocytopenia appeared in 1 patient during treatment. Overall, systemic rIFN therapy was well tolerated; its long-term administration in patients with AIDS-associated mucocutaneous KS seems to be well justified according to these preliminary observations.(ABSTRACT TRUNCATED AT 250 WORDS)
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Mayerhausen W, Ehlers G. [Pseudolymphoma following cosmetic tattooing]. Hautarzt 1986; 37:622-4. [PMID: 3542903] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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Ehlers G. [Chronic urticaria in the dermatology clinic]. Z Hautkr 1983; 58:1576-82. [PMID: 6659637] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
In order to clarify the genesis of different forms of urticaria, particular experiences of the Practicing dermatologist are required regarding allergology as well as the equipment of his practice which is of considerable importance. Certain examination methods should, however, be carried out under clinical conditions, as far as special technical instruments, comparison and reproduction of results and allergy exposition are concerned. Special regard has to be paid to the phenomenon of intolerance. Corresponding reactions are being dealt with increasingly. Even clinical treatment only produced few discoveries of allergens. Therefore, steps have to be taken to set up more effective examination techniques.
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Abstract
This paper reports a prospective randomized multicenter trial of two fractionation schemes in the supervoltage radiotherapy of locally inoperable epidermoid lung cancer. This study was stimulated by the need to provide improved and more acceptable treatment methods for patients with this condition, the most common cell type of lung cancer. The majority of such patients are not suitable for resection because of metastasis or because of extensive local disease, even though exploratory thoracotomy may be performed. It was therefore considered important to identify preferred methods of irradiation in this situation which is found in a large proportion of patients with lung cancer.
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