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Opherden D, Tepaske MSJ, Bärtl F, Weber M, Turnbull MM, Lancaster T, Blundell SJ, Baenitz M, Wosnitza J, Landee CP, Moessner R, Luitz DJ, Kühne H. Field-Tunable Berezinskii-Kosterlitz-Thouless Correlations in a Heisenberg Magnet. Phys Rev Lett 2023; 130:086704. [PMID: 36898116 DOI: 10.1103/physrevlett.130.086704] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Accepted: 01/18/2023] [Indexed: 06/18/2023]
Abstract
We report the manifestation of field-induced Berezinskii-Kosterlitz-Thouless (BKT) correlations in the weakly coupled spin-1/2 Heisenberg layers of the molecular-based bulk material [Cu(pz)_{2}(2-HOpy)_{2}](PF_{6})_{2}. At zero field, a transition to long-range order occurs at 1.38 K, caused by a weak intrinsic easy-plane anisotropy and an interlayer exchange of J^{'}/k_{B}≈1 mK. Because of the moderate intralayer exchange coupling of J/k_{B}=6.8 K, the application of laboratory magnetic fields induces a substantial XY anisotropy of the spin correlations. Crucially, this provides a significant BKT regime, as the tiny interlayer exchange J^{'} only induces 3D correlations upon close approach to the BKT transition with its exponential growth in the spin-correlation length. We employ nuclear magnetic resonance measurements to probe the spin correlations that determine the critical temperatures of the BKT transition as well as that of the onset of long-range order. Further, we perform stochastic series expansion quantum Monte Carlo simulations based on the experimentally determined model parameters. Finite-size scaling of the in-plane spin stiffness yields excellent agreement of critical temperatures between theory and experiment, providing clear evidence that the nonmonotonic magnetic phase diagram of [Cu(pz)_{2}(2-HOpy)_{2}](PF_{6})_{2} is determined by the field-tuned XY anisotropy and the concomitant BKT physics.
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Affiliation(s)
- D Opherden
- Hochfeld-Magnetlabor Dresden (HLD-EMFL) and Würzburg-Dresden Cluster of Excellence ct.qmat, Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany
| | - M S J Tepaske
- Physikalisches Institut, Universität Bonn, Nussallee 12, 53115 Bonn, Germany
- Max Planck Institute for the Physics of Complex Systems, 01187 Dresden, Germany
| | - F Bärtl
- Hochfeld-Magnetlabor Dresden (HLD-EMFL) and Würzburg-Dresden Cluster of Excellence ct.qmat, Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany
- Institut für Festkörper- und Materialphysik, TU Dresden, 01062 Dresden, Germany
| | - M Weber
- Max Planck Institute for the Physics of Complex Systems, 01187 Dresden, Germany
| | - M M Turnbull
- Carlson School of Chemistry, Clark University, Worcester, Massachusetts 01610, USA
| | - T Lancaster
- Department of Physics, Centre for Materials Physics, Durham University, Durham DH1 3LE, United Kingdom
| | - S J Blundell
- Clarendon Laboratory, Department of Physics, University of Oxford, Park Road, Oxford OX1 3PU, United Kingdom
| | - M Baenitz
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
| | - J Wosnitza
- Hochfeld-Magnetlabor Dresden (HLD-EMFL) and Würzburg-Dresden Cluster of Excellence ct.qmat, Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany
- Institut für Festkörper- und Materialphysik, TU Dresden, 01062 Dresden, Germany
| | - C P Landee
- Department of Physics, Clark University, Worcester, Massachusetts 01610, USA
| | - R Moessner
- Max Planck Institute for the Physics of Complex Systems, 01187 Dresden, Germany
| | - D J Luitz
- Physikalisches Institut, Universität Bonn, Nussallee 12, 53115 Bonn, Germany
- Max Planck Institute for the Physics of Complex Systems, 01187 Dresden, Germany
| | - H Kühne
- Hochfeld-Magnetlabor Dresden (HLD-EMFL) and Würzburg-Dresden Cluster of Excellence ct.qmat, Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany
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2
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Huddart BM, Onuorah IJ, Isah MM, Bonfà P, Blundell SJ, Clark SJ, De Renzi R, Lancaster T. Intrinsic Nature of Spontaneous Magnetic Fields in Superconductors with Time-Reversal Symmetry Breaking. Phys Rev Lett 2021; 127:237002. [PMID: 34936766 DOI: 10.1103/physrevlett.127.237002] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Revised: 08/27/2021] [Accepted: 10/27/2021] [Indexed: 06/14/2023]
Abstract
We present a systematic investigation of muon-stopping states in superconductors that reportedly exhibit spontaneous magnetic fields below their transition temperatures due to time-reversal symmetry breaking. These materials include elemental rhenium, several intermetallic systems, and Sr_{2}RuO_{4}. We demonstrate that the presence of the muon leads to only a limited and relatively localized perturbation to the local crystal structure, while any small changes to the electronic structure occur several electron volts below the Fermi energy, leading to only minimal changes in the charge density on ions close to the muon. Our results imply that the muon-induced perturbation alone is unlikely to lead to the observed spontaneous fields in these materials, whose origin is more likely intrinsic to the time-reversal symmetry-broken superconducting state.
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Affiliation(s)
- B M Huddart
- Department of Physics, Centre for Materials Physics, Durham University, Durham DH1 3LE, United Kingdom
| | - I J Onuorah
- Department of Mathematical, Physical and Computer Sciences, University of Parma, 43124 Parma, Italy
| | - M M Isah
- Department of Mathematical, Physical and Computer Sciences, University of Parma, 43124 Parma, Italy
| | - P Bonfà
- Department of Mathematical, Physical and Computer Sciences, University of Parma, 43124 Parma, Italy
| | - S J Blundell
- Department of Physics, Clarendon Laboratory, Oxford University, Parks Road, Oxford OX1 3PU, United Kingdom
| | - S J Clark
- Department of Physics, Centre for Materials Physics, Durham University, Durham DH1 3LE, United Kingdom
| | - R De Renzi
- Department of Mathematical, Physical and Computer Sciences, University of Parma, 43124 Parma, Italy
| | - T Lancaster
- Department of Physics, Centre for Materials Physics, Durham University, Durham DH1 3LE, United Kingdom
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3
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Wilkinson JM, Blundell SJ. Information and Decoherence in a Muon-Fluorine Coupled System. Phys Rev Lett 2020; 125:087201. [PMID: 32909793 DOI: 10.1103/physrevlett.125.087201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Accepted: 07/21/2020] [Indexed: 06/11/2023]
Abstract
The unitary evolution of a quantum system preserves its coherence, but interactions between the system and its environment result in decoherence, a process in which the quantum information stored in the system becomes degraded. A spin-polarized positively charged muon implanted in a fluoride crystal realizes such a coherent quantum system, and the entanglement of muon and nearest-neighbor fluorine nuclear spins gives rise to an oscillatory time dependence of the muon polarization that can be detected and measured. Here we show that the decohering effect of more distant nuclear spins can be modelled quantitatively, allowing a very detailed description of the decoherence processes coupling the muon-fluorine "system" with its "environment," and allowing us to track the system entropy as the quantum information degrades. These results show how to precisely quantify the spin relaxation of muons implanted into quantum entangled states in fluoride crystals.
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Affiliation(s)
- J M Wilkinson
- Clarendon Laboratory, University of Oxford Department of Physics, Parks Road, Oxford OX1 3PU, United Kingdom
| | - S J Blundell
- Clarendon Laboratory, University of Oxford Department of Physics, Parks Road, Oxford OX1 3PU, United Kingdom
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Adroja DT, Blundell SJ, Lang F, Luo H, Wang ZC, Cao GH. Observation of a neutron spin resonance in the bilayered superconductor CsCa 2Fe 4As 4F 2. J Phys Condens Matter 2020; 32:435603. [PMID: 32756017 DOI: 10.1088/1361-648x/aba28f] [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: 03/30/2020] [Accepted: 07/03/2020] [Indexed: 06/11/2023]
Abstract
We report inelastic neutron scattering (INS) investigations on the bilayer Fe-based superconductor CsCa2Fe4As4F2above and below its superconducting transition temperatureTc≈ 28.9 K to investigate the presence of a neutron spin resonance. This compound crystallises in a body-centred tetragonal lattice containing asymmetric double layers of Fe2As2separated by insulating CaF2layers and is known to be highly anisotropic. Our INS study clearly reveals the presence of a neutron spin resonance that exhibits higher intensity at lower momentum transfer (Q) at 5 K compared to 54 K, at an energy of 15 meV. The energyERof the observed spin resonance is broadly consistent with the relationshipER= 4.9kBTc, but is slightly enhanced compared to the values observed in other Fe-based superconductors. We discuss the nature of the electron pairing symmetry by comparing the value ofERwith that deduced from the total superconducting gap value integrated over the Fermi surface.
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Affiliation(s)
- D T Adroja
- ISIS Facility, STFC Rutherford Appleton Laboratory, Chilton, Oxfordshire OX11 0QX, United Kingdom
- Highly Correlated Matter Research Group, Physics Department, University of Johannesburg, PO Box 524, Auckland Park 2006, South Africa
| | - S J Blundell
- Department of Physics, Clarendon Laboratory, Oxford University, Parks Road, Oxford OX1 3PU, United Kingdom
| | - F Lang
- ISIS Facility, STFC Rutherford Appleton Laboratory, Chilton, Oxfordshire OX11 0QX, United Kingdom
- Department of Physics, Clarendon Laboratory, Oxford University, Parks Road, Oxford OX1 3PU, United Kingdom
| | - H Luo
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, People's Republic of China
| | - Z-C Wang
- Department of Physics and State Key Lab of Silicon Materials, Zhejiang University, Hangzhou 310027, People's Republic of China
| | - G-H Cao
- Department of Physics and State Key Lab of Silicon Materials, Zhejiang University, Hangzhou 310027, People's Republic of China
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Lancaster T, Huddart BM, Williams RC, Xiao F, Franke KJA, Baker PJ, Pratt FL, Blundell SJ, Schlueter JA, Mills MB, Maahs AC, Preuss KE. Probing magnetic order and disorder in the one-dimensional molecular spin chains CuF 2(pyz) and [Ln(hfac) 3(boaDTDA)] n (Ln = Sm, La) using implanted muons. J Phys Condens Matter 2019; 31:394002. [PMID: 31239417 DOI: 10.1088/1361-648x/ab2cb6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We present the results of muon-spin relaxation ([Formula: see text]SR) measurements on antiferromagnetic and ferromagnetic spin chains. In antiferromagnetic CuF2(pyz) we identify a transition to long range magnetic order taking place at [Formula: see text] K, allowing us to estimate a ratio with the intrachain exchange of [Formula: see text] and the ratio of interchain to intrachain exchange coupling as [Formula: see text]. The ferromagnetic chain [Sm(hfac)3(boaDTDA)] n undergoes an ordering transition at [Formula: see text] K, seen via a broad freezing of dynamic fluctuations on the muon (microsecond) timescale and implying [Formula: see text]. The ordered radical moment continues to fluctuate on this timescale down to 0.3 K, while the Sm moments remain disordered. In contrast, the radical spins in [La(hfac)3(boaDTDA)] n remain magnetically disordered down to T = 0.1 K suggesting [Formula: see text].
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Affiliation(s)
- T Lancaster
- Centre for Materials Physics, Durham University, Durham DH1 3LE, United Kingdom
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6
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Huddart BM, Birch MT, Pratt FL, Blundell SJ, Porter DG, Clark SJ, Wu W, Julian SR, Hatton PD, Lancaster T. Local magnetism, magnetic order and spin freezing in the 'nonmetallic metal' FeCrAs. J Phys Condens Matter 2019; 31:285803. [PMID: 30933932 DOI: 10.1088/1361-648x/ab151f] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We present the results of x-ray scattering and muon-spin relaxation ([Formula: see text]SR) measurements on the iron-pnictide compound FeCrAs. Polarized non-resonant magnetic x-ray scattering results reveal the 120° periodicity expected from the suggested three-fold symmetric, non-collinear antiferromagnetic structure. [Formula: see text]SR measurements indicate a magnetically ordered phase throughout the bulk of the material below [Formula: see text] K. There are signs of fluctuating magnetism in a narrow range of temperatures above [Formula: see text] involving low-energy excitations, while at temperatures well below [Formula: see text] behaviour characteristic of freezing of dynamics is observed, likely reflecting the effect of disorder in our polycrystalline sample. Using density functional theory we propose a distinct muon stopping site in this compound and assess the degree of distortion induced by the implanted muon.
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Affiliation(s)
- B M Huddart
- Centre for Materials Physics, Durham University, Durham DH1 3LE, United Kingdom
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7
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Liu J, Kittaka S, Johnson RD, Lancaster T, Singleton J, Sakakibara T, Kohama Y, van Tol J, Ardavan A, Williams BH, Blundell SJ, Manson ZE, Manson JL, Goddard PA. Unconventional Field-Induced Spin Gap in an S=1/2 Chiral Staggered Chain. Phys Rev Lett 2019; 122:057207. [PMID: 30822013 DOI: 10.1103/physrevlett.122.057207] [Citation(s) in RCA: 2] [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: 08/30/2018] [Indexed: 06/09/2023]
Abstract
We investigate the low-temperature magnetic properties of the molecule-based chiral spin chain [Cu(pym)(H_{2}O)_{4}]SiF_{6}·H_{2}O (pym=pyrimidine). Electron-spin resonance, magnetometry and heat capacity measurements reveal the presence of staggered g tensors, a rich low-temperature excitation spectrum, a staggered susceptibility, and a spin gap that opens on the application of a magnetic field. These phenomena are reminiscent of those previously observed in nonchiral staggered chains, which are explicable within the sine-Gordon quantum-field theory. In the present case, however, although the sine-Gordon model accounts well for the form of the temperature dependence of the heat capacity, the size of the gap and its measured linear field dependence do not fit with the sine-Gordon theory as it stands. We propose that the differences arise due to additional terms in the Hamiltonian resulting from the chiral structure of [Cu(pym)(H_{2}O)_{4}]SiF_{6}·H_{2}O, particularly a uniform Dzyaloshinskii-Moriya coupling and a fourfold periodic staggered field.
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Affiliation(s)
- J Liu
- Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
| | - S Kittaka
- Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - R D Johnson
- Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
| | - T Lancaster
- Centre for Materials Physics, Durham University, South Road, Durham DH1 3LE, United Kingdom
| | - J Singleton
- National High Magnetic Field Laboratory, Los Alamos National Laboratory, MS-E536, Los Alamos, New Mexico 87545, USA
| | - T Sakakibara
- Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Y Kohama
- Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - J van Tol
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, USA
| | - A Ardavan
- Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
| | - B H Williams
- Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
| | - S J Blundell
- Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
| | - Z E Manson
- Department of Chemistry and Biochemistry, Eastern Washington University, Cheney, Washington 99004, USA
| | - J L Manson
- Department of Chemistry and Biochemistry, Eastern Washington University, Cheney, Washington 99004, USA
| | - P A Goddard
- Department of Physics, University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, United Kingdom
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Abstract
The experimental technique of a.c. susceptibility can be used as a probe of magnetic dynamics in a wide variety of systems. Its use is restricted to the low-frequency regime and thus is sensitive to relatively slow processes. Rather than measuring the dynamics of single spins, a.c. susceptibility can be used to probe the dynamics of collective objects, such as domain walls in ferromagnets or vortex matter in superconductors. In some frustrated systems, such as spin glasses, the complex interactions lead to substantial spectral weight of fluctuations in the low-frequency regime, and thus a.c. susceptibility can play a unique role. We review the theory underlying the technique and magnetic dynamics more generally and give applications of a.c. susceptibility to a wide variety of experimental situations.
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9
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Williams RC, Xiao F, Thomas IO, Clark SJ, Lancaster T, Cornish GA, Blundell SJ, Hayes W, Paul AK, Felser C, Jansen M. Muon-spin relaxation study of the double perovskite insulators Sr2 BOsO6 (B = Fe, Y, ln). J Phys Condens Matter 2016; 28:076001. [PMID: 26807612 DOI: 10.1088/0953-8984/28/7/076001] [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: 06/05/2023]
Abstract
We present the results of zero-field muon-spin relaxation measurements made on the double perovskite insulators Sr2 BOsO6 (B = Fe,Y, In). Spontaneous muon-spin precession indicative of quasistatic long range magnetic ordering is observed in Sr2FeOsO6 within the AF1 antiferromagnetic phase for temperatures below [Formula: see text] K. Upon cooling below T2≈67 K the oscillations cease to be resolvable owing to the coexistence of the AF1 and AF2 phases, which leads to a broader range of internal magnetic fields. Using density functional calculations we identify a candidate muon stopping site within the unit cell, which dipole field simulations show to be consistent with the proposed magnetic structure. The possibility of incommensurate magnetic ordering is discussed for temperatures below TN = 53 K and 25 K for Sr2YOsO6 and Sr2InOsO6, respectively.
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Affiliation(s)
- R C Williams
- Department of Physics, Durham University, South Road, Durham, DH1 3LE, UK
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10
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Foronda FR, Lang F, Möller JS, Lancaster T, Boothroyd AT, Pratt FL, Giblin SR, Prabhakaran D, Blundell SJ. Anisotropic local modification of crystal field levels in Pr-based pyrochlores: a muon-induced effect modeled using density functional theory. Phys Rev Lett 2015; 114:017602. [PMID: 25615502 DOI: 10.1103/physrevlett.114.017602] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2014] [Indexed: 06/04/2023]
Abstract
Although muon spin relaxation is commonly used to probe local magnetic order, spin freezing, and spin dynamics, we identify an experimental situation in which the measured response is dominated by an effect resulting from the muon-induced local distortion rather than the intrinsic behavior of the host compound. We demonstrate this effect in some quantum spin ice candidate materials Pr(2)B(2)O(7) (B=Sn, Zr, Hf), where we detect a static distribution of magnetic moments that appears to grow on cooling. Using density functional theory we show how this effect can be explained via a hyperfine enhancement arising from a splitting of the non-Kramers doublet ground states on Pr ions close to the muon, which itself causes a highly anisotropic distortion field. We provide a quantitative relationship between this effect and the measured temperature dependence of the muon relaxation and discuss the relevance of these observations to muon experiments in other magnetic materials.
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Affiliation(s)
- F R Foronda
- Oxford University Department of Physics, Clarendon Laboratory, Parks Road, Oxford OX1 3PU, United Kingdom
| | - F Lang
- Oxford University Department of Physics, Clarendon Laboratory, Parks Road, Oxford OX1 3PU, United Kingdom
| | - J S Möller
- Oxford University Department of Physics, Clarendon Laboratory, Parks Road, Oxford OX1 3PU, United Kingdom
| | - T Lancaster
- Durham University, Centre for Materials Physics, South Road, Durham DH1 3LE, United Kingdom
| | - A T Boothroyd
- Oxford University Department of Physics, Clarendon Laboratory, Parks Road, Oxford OX1 3PU, United Kingdom
| | - F L Pratt
- ISIS Facility, Rutherford Appleton Laboratory, Chilton, Oxfordshire OX11 0QX, United Kingdom
| | - S R Giblin
- School of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA, United Kingdom
| | - D Prabhakaran
- Oxford University Department of Physics, Clarendon Laboratory, Parks Road, Oxford OX1 3PU, United Kingdom
| | - S J Blundell
- Oxford University Department of Physics, Clarendon Laboratory, Parks Road, Oxford OX1 3PU, United Kingdom
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Pratt FL, Lancaster T, Blundell SJ, Baines C. Low-field superconducting phase of (TMTSF)2ClO4. Phys Rev Lett 2013; 110:107005. [PMID: 23521285 DOI: 10.1103/physrevlett.110.107005] [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] [Received: 10/04/2012] [Revised: 01/04/2013] [Indexed: 06/01/2023]
Abstract
The low-field phase of the organic superconductor (TMTSF)(2)ClO(4) is studied by muon-spin rotation. The zero temperature limit of the magnetic penetration depth within the TMTSF layers is obtained to be λ(ab)(0) = 0.86(2) μm. Temperature dependence of the muon-spin relaxation shows no indication of gap nodes on the Fermi surface nor of any spontaneous fields due to time-reversal-symmetry breaking. The weight of evidence suggests that the symmetry of this low-field phase is odd-frequency p-wave singlet, a novel example of odd-frequency pairing in a bulk superconductor.
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Affiliation(s)
- F L Pratt
- ISIS Facility, STFC Rutherford Appleton Laboratory, Chilton, Oxfordshire OX11 0QX, United Kingdom
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12
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Choi SK, Coldea R, Kolmogorov AN, Lancaster T, Mazin II, Blundell SJ, Radaelli PG, Singh Y, Gegenwart P, Choi KR, Cheong SW, Baker PJ, Stock C, Taylor J. Spin waves and revised crystal structure of honeycomb iridate Na2IrO3. Phys Rev Lett 2012; 108:127204. [PMID: 22540621 DOI: 10.1103/physrevlett.108.127204] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2011] [Indexed: 05/31/2023]
Abstract
We report inelastic neutron scattering measurements on Na2IrO3, a candidate for the Kitaev spin model on the honeycomb lattice. We observe spin-wave excitations below 5 meV with a dispersion that can be accounted for by including substantial further-neighbor exchanges that stabilize zigzag magnetic order. The onset of long-range magnetic order below T(N)=15.3 K is confirmed via the observation of oscillations in zero-field muon-spin rotation experiments. Combining single-crystal diffraction and density functional calculations we propose a revised crystal structure model with significant departures from the ideal 90° Ir-O-Ir bonds required for dominant Kitaev exchange.
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Affiliation(s)
- S K Choi
- Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
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13
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Wedge CJ, Timco GA, Spielberg ET, George RE, Tuna F, Rigby S, McInnes EJL, Winpenny REP, Blundell SJ, Ardavan A. Chemical engineering of molecular qubits. Phys Rev Lett 2012; 108:107204. [PMID: 22463450 DOI: 10.1103/physrevlett.108.107204] [Citation(s) in RCA: 153] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2011] [Indexed: 05/05/2023]
Abstract
We show that the electron spin phase memory time, the most important property of a molecular nanomagnet from the perspective of quantum information processing, can be improved dramatically by chemically engineering the molecular structure to optimize the environment of the spin. We vary systematically each structural component of the class of antiferromagnetic Cr(7)Ni rings to identify the sources of decoherence. The optimal structure exhibits a phase memory time exceeding 15 μs.
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Affiliation(s)
- C J Wedge
- Centre for Advanced Electron Spin Resonance, Clarendon Laboratory, Department of Physics, University of Oxford, OX1 3PU, United Kingdom
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14
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Lord JS, McKenzie I, Baker PJ, Blundell SJ, Cottrell SP, Giblin SR, Good J, Hillier AD, Holsman BH, King PJC, Lancaster T, Mitchell R, Nightingale JB, Owczarkowski M, Poli S, Pratt FL, Rhodes NJ, Scheuermann R, Salman Z. Design and commissioning of a high magnetic field muon spin relaxation spectrometer at the ISIS pulsed neutron and muon source. Rev Sci Instrum 2011; 82:073904. [PMID: 21806196 DOI: 10.1063/1.3608114] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The high magnetic field (HiFi) muon instrument at the ISIS pulsed neutron and muon source is a state-of-the-art spectrometer designed to provide applied magnetic fields up to 5 T for muon studies of condensed matter and molecular systems. The spectrometer is optimised for time-differential muon spin relaxation studies at a pulsed muon source. We describe the challenges involved in its design and construction, detailing, in particular, the magnet and detector performance. Commissioning experiments have been conducted and the results are presented to demonstrate the scientific capabilities of the new instrument.
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Affiliation(s)
- J S Lord
- ISIS Facility, STFC Rutherford Appleton Laboratory, Chilton, Oxon OX11 0QX, United Kingdom
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15
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Lancaster T, Möller JS, Blundell SJ, Pratt FL, Baker PJ, Guidi T, Timco GA, Winpenny REP. Observation of a level crossing in a molecular nanomagnet using implanted muons. J Phys Condens Matter 2011; 23:242201. [PMID: 21628784 DOI: 10.1088/0953-8984/23/24/242201] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We have observed an electronic energy level crossing in a molecular nanomagnet (MNM) using muon spin relaxation. This effect, not observed previously despite several muon studies of MNM systems, provides further evidence that the spin relaxation of the implanted muon is sensitive to the dynamics of the electronic spin. Our measurements on a broken ring MNM [H(2)N(t)Bu(is)Pr][Cr(8)CdF(9)(O(2)CC(CH(3))(3))(18)], which contains eight Cr ions, show clear evidence for the S = 0 --> S = 1 transition that takes place at B(c) = 2.3 T. The crossing is observed as a resonance-like dip in the average positron asymmetry and also in the muon spin relaxation rate, which shows a sharp increase in magnitude at the transition and a peak centred within the S = 1 regime.
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Affiliation(s)
- T Lancaster
- Clarendon Laboratory, Oxford University Department of Physics, Oxford, UK.
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Lancaster T, Pratt FL, Blundell SJ, McKenzie I, Assender HE. Muon-fluorine entanglement in fluoropolymers. J Phys Condens Matter 2009; 21:346004. [PMID: 21715794 DOI: 10.1088/0953-8984/21/34/346004] [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 the results of muon spin relaxation measurements on the fluoropolymers polytetrafluoroethylene (PTFE), poly(vinylidene fluoride) (PVDF) and poly(vinyl fluoride) (PVF). Entanglement between the muon spin and the spins of the fluorine nuclei in the polymers allows us to identify the different muon stopping states that occur in each of these materials and provides a method of probing the local environment of the muon and the dynamics of the polymer chains.
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Affiliation(s)
- T Lancaster
- Department of Physics, Clarendon Laboratory, Oxford University, Parks Road, Oxford OX1 3PU, UK
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Drew AJ, Niedermayer C, Baker PJ, Pratt FL, Blundell SJ, Lancaster T, Liu RH, Wu G, Chen XH, Watanabe I, Malik VK, Dubroka A, Rössle M, Kim KW, Baines C, Bernhard C. Coexistence of static magnetism and superconductivity in SmFeAsO(1-x)F(x) as revealed by muon spin rotation. Nat Mater 2009; 8:310-314. [PMID: 19234446 DOI: 10.1038/nmat2396] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2008] [Accepted: 01/20/2009] [Indexed: 05/27/2023]
Abstract
The recent observation of superconductivity with critical temperatures (Tc) up to 55 K in the pnictide RFeAsO(1-x)F(x), where R is a lanthanide, marks the first discovery of a non-copper-oxide-based layered high-Tc superconductor. It has raised the suspicion that these new materials share a similar pairing mechanism to the cuprate superconductors, as both families exhibit superconductivity following charge doping of a magnetic parent material. In this context, it is important to follow the evolution of the microscopic magnetic properties of the pnictides with doping and hence to determine whether magnetic correlations coexist with superconductivity. Here, we present a muon spin rotation study on SmFeAsO(1-x)F(x), with x=0-0.30 that shows that, as in the cuprates, static magnetism persists well into the superconducting regime. This analogy is quite surprising as the parent compounds of the two families have rather different magnetic ground states: itinerant spin density wave for the pnictides contrasted with the Mott-Hubbard insulator in the cuprates. Our findings therefore suggest that the proximity to magnetic order and associated soft magnetic fluctuations, rather than strong electronic correlations in the vicinity of a Mott-Hubbard transition, may be the key ingredients of high-Tc superconductors.
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Affiliation(s)
- A J Drew
- University of Fribourg, Department of Physics and Fribourg Centre for Nanomaterials, Chemin du Musée 3, CH-1700 Fribourg, Switzerland.
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Baker PJ, Lancaster T, Blundell SJ, Pratt FL, Brooks ML, Kwon SJ. Tuning the interlayer spacing of high-T_{c} Bi-based superconductors by intercalation: measuring the penetration depth and the two-dimensional superfluid density. Phys Rev Lett 2009; 102:087002. [PMID: 19257777 DOI: 10.1103/physrevlett.102.087002] [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] [Received: 07/03/2008] [Indexed: 05/27/2023]
Abstract
Substantial control of the interlayer spacing in Bi-based high temperature superconductors has been achieved through the intercalation of guest molecules between the superconducting layers. Measurements using implanted muons reveal that the penetration depth increases with increasing layer separation while T_{c} does not vary appreciably, demonstrating that the bulk superfluid density is not the determining factor controlling T_{c}. Our results strongly suggest that for Bi-based high temperature superconductors the superfluid density appearing in the Uemura scaling relation rho_{s} proportional, variantT_{c} should be interpreted as the two-dimensional density within the superconducting layers, which we find to be constant for each class of system investigated.
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Affiliation(s)
- P J Baker
- Department of Physics, Oxford University, Clarendon Laboratory, Parks Road, Oxford, OX1 3PU, United Kingdom
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Baker PJ, Lancaster T, Blundell SJ, Hayes W, Pratt FL, Itoh M, Kuroiwa S, Akimitsu J. Muon spin relaxation study of LaTiO(3) and YTiO(3). J Phys Condens Matter 2008; 20:465203. [PMID: 21693843 DOI: 10.1088/0953-8984/20/46/465203] [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: 05/30/2023]
Abstract
We report muon spin relaxation (μSR) measurements on two Ti(3+) containing perovskites, LaTiO(3) and YTiO(3), which display long-range magnetic order at low temperature. For both materials, oscillations in the time dependence of the muon polarization are observed which are consistent with three-dimensional magnetic order. From our data we identify two magnetically inequivalent muon stopping sites. The μSR results are compared with the magnetic structures of these compounds previously derived from neutron diffraction and μSR studies on structurally similar compounds.
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Affiliation(s)
- P J Baker
- Department of Physics, Oxford University, Parks Road, Oxford OX1 3PU, UK
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Drew AJ, Pratt FL, Lancaster T, Blundell SJ, Baker PJ, Liu RH, Wu G, Chen XH, Watanabe I, Malik VK, Dubroka A, Kim KW, Rössle M, Bernhard C. Coexistence of magnetic fluctuations and superconductivity in the pnictide high temperature superconductor SmFeAsO1-xFx measured by muon spin rotation. Phys Rev Lett 2008; 101:097010. [PMID: 18851648 DOI: 10.1103/physrevlett.101.097010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2008] [Indexed: 05/26/2023]
Abstract
Muon spin rotation experiments were performed on the pnictide high temperature superconductor SmFeAsO1-xFx with x=0.18 and 0.3. We observed an unusual enhancement of slow spin fluctuations in the vicinity of the superconducting transition which suggests that the spin fluctuations contribute to the formation of an unconventional superconducting state. An estimate of the in-plane penetration depth lambda ab(0)=190(5) nm was obtained, which confirms that the pnictide superconductors obey an Uemura-style relationship between Tc and lambda ab(0);(-2).
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Affiliation(s)
- A J Drew
- Department of Physics and Fribourg Center for Nanomaterials, University of Fribourg, Chemin du Musee 3, CH-1700 Fribourg, Switzerland
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Lancaster T, Blundell SJ, Baker PJ, Brooks ML, Hayes W, Pratt FL, Coldea R, Sörgel T, Jansen M. Anomalous temperature evolution of the internal magnetic field distribution in the charge-ordered triangular antiferromagnet AgNiO2. Phys Rev Lett 2008; 100:017206. [PMID: 18232815 DOI: 10.1103/physrevlett.100.017206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2007] [Indexed: 05/25/2023]
Abstract
Zero-field muon-spin relaxation measurements of the frustrated triangular quantum magnet AgNiO2 are consistent with a model of charge disproportionation that has been advanced to explain the structural and magnetic properties of this compound. Below an ordering temperature of TN=19.9(2) K we observe six distinct muon precession frequencies, due to the magnetic order, which can be accounted for with a model describing the probable muon sites. The precession frequencies show an unusual temperature evolution which is suggestive of the separate evolution of two opposing magnetic sublattices.
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Affiliation(s)
- T Lancaster
- Clarendon Laboratory, Oxford University Department of Physics, Parks Road, Oxford OX1 3PU, United Kingdom.
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Lancaster T, Blundell SJ, Baker PJ, Brooks ML, Hayes W, Pratt FL, Manson JL, Conner MM, Schlueter JA. Muon-fluorine entangled states in molecular magnets. Phys Rev Lett 2007; 99:267601. [PMID: 18233603 DOI: 10.1103/physrevlett.99.267601] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2007] [Indexed: 05/25/2023]
Abstract
The information accessible from a muon-spin relaxation experiment can be limited due to a lack of knowledge of the precise muon stopping site. We demonstrate here the possibility of localizing a spin polarized muon in a known stopping state in a molecular material containing fluorine. The muon-spin precession that results from the entangled nature of the muon spin and surrounding nuclear spins is sensitive to the nature of the stopping site. We use this property to identify three classes of sites that occur in molecular magnets and describe the extent to which the muon distorts its surroundings.
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Affiliation(s)
- T Lancaster
- Clarendon Laboratory, Department of Physics, Oxford University, Parks Road, Oxford, OX1 3PU, United Kingdom.
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Singleton J, Goddard PA, Ardavan A, Coldea AI, Blundell SJ, McDonald RD, Tozer S, Schlueter JA. Persistence to high temperatures of interlayer coherence in an organic superconductor. Phys Rev Lett 2007; 99:027004. [PMID: 17678248 DOI: 10.1103/physrevlett.99.027004] [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: 10/11/2006] [Indexed: 05/16/2023]
Abstract
The interlayer magnetoresistance rho(zz) of the organic metal kappa-(BEDT-TTF)(2)Cu(NCS)(2) is studied in fields of up to 45 T and at temperatures T from 0.5 to 30 K. The peak in rho(zz) seen in in-plane fields, a definitive signature of interlayer coherence, remains to Ts exceeding the Anderson criterion for incoherent transport by a factor approximately 30. Angle-dependent magnetoresistance oscillations are modeled using an approach based on field-induced quasiparticle paths on a 3D Fermi surface, to yield the T dependence of the scattering rate tau(-1). The results suggest that tau(-1) does not vary strongly over the Fermi surface, and that it has a T(2) dependence due to electron-electron scattering.
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Affiliation(s)
- John Singleton
- National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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Pratt FL, Baker PJ, Blundell SJ, Lancaster T, Green MA, Kurmoo M. Chiral-like critical behavior in the antiferromagnet cobalt glycerolate. Phys Rev Lett 2007; 99:017202. [PMID: 17678186 DOI: 10.1103/physrevlett.99.017202] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2007] [Indexed: 05/16/2023]
Abstract
Critical exponents closely matching those of the N=2 chiral universality class have been obtained for the layered magnetic system cobalt glycerolate using muon spin relaxation. This class was originally introduced to represent geometrically frustrated triangular stacked-layer XY magnets with chiral noncollinear spin structures. Since the present magnetic system is a canted XY system without geometrical frustration or chiral degeneracy, the results indicate that the order parameter for canting in this system plays a similar role to the chiral order parameter in the geometrically frustrated systems, strongly suggesting that both types of noncollinear system share the same universality class.
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Affiliation(s)
- F L Pratt
- ISIS Facility, Rutherford Appleton Laboratory, Chilton, Oxfordshire, United Kingdom
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Lancaster T, Blundell SJ, Andreica D, Janoschek M, Roessli B, Gvasaliya SN, Conder K, Pomjakushina E, Brooks ML, Baker PJ, Prabhakaran D, Hayes W, Pratt FL. Magnetism in geometrically frustrated YMnO3 under hydrostatic pressure studied with muon spin relaxation. Phys Rev Lett 2007; 98:197203. [PMID: 17677657 DOI: 10.1103/physrevlett.98.197203] [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: 10/17/2006] [Indexed: 05/16/2023]
Abstract
The ferroelectromagnet YMnO3 consists of weakly coupled triangular layers of S=2 spins. Below T(N) approximately equal to 70 K muon-spin relaxation data show two oscillatory relaxing signals due to magnetic order, with no purely relaxing signals resolvable (which would require different coexisting spin distributions). The transition temperature T(N) increases with applied hydrostatic pressure, even though the ordered moment decreases. These results suggest that pressure increases both the exchange coupling between the layers and the frustration within the layers.
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Affiliation(s)
- T Lancaster
- Clarendon Laboratory, Department of Physics, Oxford University, Parks Road, Oxford, OX1 3PU, United Kingdom.
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Manson JL, Lancaster T, Schlueter JA, Blundell SJ, Brooks ML, Pratt FL, Nygren CL, Koo HJ, Dai D, Whangbo MH. Characterization of the Crystal and Magnetic Structures of the Mixed-Anion Coordination Polymer Cu(HCO2)(NO3)(pyz) {pyz = Pyrazine} by X-ray Diffraction, ac Magnetic Susceptibility, dc Magnetization, Muon-Spin Relaxation, and Spin Dimer Analysis. Inorg Chem 2006; 46:213-20. [PMID: 17198430 DOI: 10.1021/ic061590q] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The mixed-anion coordination polymer Cu(HCO2)(NO3)(pyz) was synthesized, its crystal structure was determined by X-ray diffraction, and its magnetic structure was characterized by ac susceptibility, dc magnetization, muon-spin relaxation, and spin dimer analysis. The crystal structure consists of five-coordinate Cu2+ ions that are connected through syn-anti bridging mu-HCO2- and mu-pyz ligands to form a highly corrugated two-dimensional layered network. Bulk magnetic measurements show a broad maximum in chi(T) at 6.6 K. The HCO2- and pyz ligands mediate ferromagnetic and antiferromagnetic spin exchange interactions between adjacent Cu2+ ions with the spin exchange parameters J/kB = 8.17 and -5.4 K, respectively (H = -JSigmaSi x Sj). The muon-spin relaxation data show a transition to a long-range magnetic ordering below TN = 3.66(3) K. For T < TN, the M(H) and chi'ac measurements provide evidence for a field-induced spin-flop transition at 15.2 kOe. That Cu(HCO2)(NO3)(pyz) undergoes a long-range magnetic ordering is an unexpected result because the one-dimensional Cu(NO3)2(pyz) and three-dimensional Cu(HCO2)2(pyz) compounds display linear chain antiferromagnetism with no long-range magnetic ordering down to 2 K.
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Affiliation(s)
- J L Manson
- Condensed Matter Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA. jmanson@ ewu.edu
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Pratt FL, Blundell SJ, Lancaster T, Baines C, Takagi S. Low-temperature spin diffusion in a highly ideal S=1/2 Heisenberg antiferromagnetic chain studied by muon spin relaxation. Phys Rev Lett 2006; 96:247203. [PMID: 16907276 DOI: 10.1103/physrevlett.96.247203] [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: 03/22/2006] [Indexed: 05/11/2023]
Abstract
The organic radical-ion salt DEOCC-TCNQF4 contains linear chains of stacked molecules with significant Heisenberg antiferromagnet interactions along the chain and extremely weak interactions between the chains. Zero-field muSR has confirmed the absence of long-range magnetic order down to 20 mK and field-dependent muSR is found to be consistent with diffusive motion of the spin excitations. The anisotropic spin dynamics and the upper boundary for magnetic ordering temperature both indicate interchain magnetic coupling /J'/<7 mK. As the intrachain coupling J is 110 K, /J'/J/ is significantly less than 10(-4). This system therefore provides one of the most ideal examples of the one-dimensional S=1/2 Heisenberg antiferromagnet yet discovered.
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Affiliation(s)
- F L Pratt
- ISIS Facility, Rutherford Appleton Laboratory, Chilton, Oxfordshire OX11 0QX, United Kingdom
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Abstract
Scaling relations between the superconducting transition temperature T(c), the superfluid stiffness rho(s), and the normal state conductivity sigma(0)(T(c)) are identified within the class of molecular superconductors. These new scaling properties hold as T(c) varies over 2 orders of magnitude for materials with differing dimensionality and contrasting molecular structure and are dramatically different from the equivalent scaling properties observed for cuprate superconductors. These scaling relations place strong constraints on theories for molecular superconductivity.
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Affiliation(s)
- F L Pratt
- ISIS Facility, Rutherford Appleton Laboratory, Chilton, Oxfordshire OX11 0QX, United Kingdom.
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Manson JL, Lancaster T, Chapon LC, Blundell SJ, Schlueter JA, Brooks ML, Pratt FL, Nygren CL, Qualls JS. Cu(HCO2)2(pym) (pym = pyrimidine): Low-Dimensional Magnetic Behavior and Long-Range Ordering in a Quantum-Spin Lattice. Inorg Chem 2005; 44:989-95. [PMID: 15859278 DOI: 10.1021/ic048723x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We synthesized and structurally and magnetically characterized the novel 3D coordination polymer Cu(HCO2)2(pym) (pym = pyrimidine). The compound crystallizes in the monoclinic space group C2/c with a = 14.4639(8) A, b = 7.7209(4) A, c = 8.5172(5) A, beta = 126.076(2) degrees, and V= 768.76(7) A3. In the structure buckled layers of Cu(HCO2)2 are interconnected by pym ligands to afford 1D Cu-pym-Cu chains. Bulk magnetic susceptibility measurements show a broad maximum at 25 K that is indicative of short-range magnetic ordering. Between 12 and 300 K a least-squares fit of the chi(T) data to a mean-field-corrected antiferromagnetic chain model yielded excellent agreement for g = 2.224(3), J/kB = -26.9(2) K, and zJ'/kB = -1.1(3) K. Below approximately 3 K a transition to long-range magnetic ordering is observed, as suggested by a sharp and sudden decrease in chi(T). This result is corroborated by muon spin relaxation measurements that show oscillations in the muon asymmetry below T(N) = 2.802(1) K and rapidly fluctuating moments above T(N).
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Affiliation(s)
- J L Manson
- Department of Chemistry and Biochemistry, Eastern Washington University, Cheney, Washington 99004, USA.
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Blundell SJ, Lancaster T, Pratt FL, Steer CA, Brooks ML, Letard JF. Dynamic and static muon-spin relaxation observed above and below the spin-crossover in Fe(II) complexes. ACTA ACUST UNITED AC 2004. [DOI: 10.1051/jp4:2004114143] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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Coldea AI, Blundell SJ, Steer CA, Mitchell JF, Pratt FL. Spin freezing and magnetic inhomogeneities in bilayer manganites. Phys Rev Lett 2002; 89:277601. [PMID: 12513240 DOI: 10.1103/physrevlett.89.277601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2002] [Indexed: 05/24/2023]
Abstract
We have performed a muon spin rotation study on polycrystalline samples of electron-doped layered manganites, La2-2xSr1+2xMn2O7 (0.4< or =x<1), in order to investigate the local magnetic structure and spin dynamics. Our results provide evidence for phase separation into A-type antiferromagnetic and charge-ordered phases for x=0.52 and spin freezing at low temperatures (T<100 K) for 0.52< or =x<0.75. A new phase diagram which includes this spin-freezing region is proposed.
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Affiliation(s)
- A I Coldea
- Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
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Hayward MA, Cussen EJ, Claridge JB, Bieringer M, Rosseinsky MJ, Kiely CJ, Blundell SJ, Marshall IM, Pratt FL. The hydride anion in an extended transition metal oxide array: LaSrCoO3H0.7. Science 2002; 295:1882-4. [PMID: 11884751 DOI: 10.1126/science.1068321] [Citation(s) in RCA: 228] [Impact Index Per Article: 10.4] [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
We present the synthesis and structural characterization of a transition metal oxide hydride, LaSrCoO3H0.7, which adopts an unprecedented structure in which oxide chains are bridged by hydride anions to form a two-dimensional extended network. The metal centers are strongly coupled by their bonding with both oxide and hydride ligands to produce magnetic ordering at temperatures up to at least 350 kelvin. The synthetic route is sufficiently general to allow the prediction of a new class of transition metal--containing electronic and magnetic materials.
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Affiliation(s)
- M A Hayward
- Department of Chemistry, University of Liverpool, Liverpool L69 7ZD, UK
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Singleton J, Goddard PA, Ardavan A, Harrison N, Blundell SJ, Schlueter JA, Kini AM. Test for interlayer coherence in a quasi-two-dimensional superconductor. Phys Rev Lett 2002; 88:037001. [PMID: 11801081 DOI: 10.1103/physrevlett.88.037001] [Citation(s) in RCA: 11] [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: 04/30/2001] [Indexed: 05/23/2023]
Abstract
Peaks in the magnetoresistivity of the layered superconductor kappa - (BEDT-TTF)2Cu(NCS)(2), measured in fields < or =45 T applied within the layers, show that the Fermi surface is extended in the interlayer direction and enable the interlayer transfer integral (t( perpendicular) approximately 0.04 meV) to be deduced. However, the quasiparticle scattering rate tau(-1) is such that Planck's over 2pi/tau approximately 6t( perpendicular), implying that kappa - (BEDT-TTF)2Cu(NCS)(2) meets the criterion used to identify interlayer incoherence. The applicability of this criterion to anisotropic materials is thus shown to be questionable.
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Affiliation(s)
- John Singleton
- National High Magnetic Field Laboratory, LANL, MS-E536, Los Alamos, New Mexico 87545, USA
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Battle PD, Bell AM, Blundell SJ, Coldea AI, Cussen EJ, Hardy GC, Marshall IM, Rosseinsky MJ, Steer CA. Chemically induced magnetism and magnetoresistance in La(0.8)Sr(1.2)Mn(0.6)Rh(0.4)O(4). J Am Chem Soc 2001; 123:7610-5. [PMID: 11480982 DOI: 10.1021/ja010958+] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
It is shown by magnetometry and microSR spectroscopy that short-range magnetic interactions between the Mn cations in the nonmetallic K(2)NiF(4)-like phase La(0.8)Sr(1.2)Mn(0.6)Rh(0.4)O(4) become significant below approximately 200 K. Negative magnetoresistance (rho/rho(0) approximately 0.5 in 14 T at 108 K) is apparent below this temperature. Neutron diffraction has shown that an applied magnetic field of 5 T is sufficient to induce saturated (3.38(7)mu(B) per Mn) long-range ferromagnetic ordering of the atomic moments at 2 K, and that the induced ordering persists up to a temperature of 50 K in 5 T. Spin glass behavior is observed below 20 K in the absence of an applied field. The induced magnetic ordering is attributed to the subtle changes in band structure brought about by the external field, and to the controlling influence of Rh(3+) over the relative strength of competing magnetic exchange interactions.
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Affiliation(s)
- P D Battle
- Inorganic Chemistry Laboratory, Chemistry Department, University of Oxford, South Parks Road, Oxford OX1 3QR, UK
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Cussen EJ, Rosseinsky MJ, Battle PD, Burley JC, Spring LE, Vente JF, Blundell SJ, Coldea AI, Singleton J. Control of magnetic ordering by Jahn--Teller distortions in Nd(2)GaMnO(6) and La(2)GaMnO(6). J Am Chem Soc 2001; 123:1111-22. [PMID: 11456664 DOI: 10.1021/ja003139i] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The substitution of Ga(3+) into the Jahn--Teller distorted, antiferromagnetic perovskites LaMnO(3) and NdMnO(3) strongly affects both the crystal structures and resulting magnetic ordering. In both compounds the Ga(3+) and Mn(3+) cations are disordered over the six coordinate sites. La(2)GaMnO(6) is a ferromagnetic insulator (T(c) = 70 K); a moment per Mn cation of 2.08(5) mu(B) has been determined by neutron powder diffraction at 5 K. Bond length and displacement parameter data suggest Jahn--Teller distortions which are both coherent and incoherent with the Pnma space group symmetry of the perovskite structure (a = 5.51122(4) A, b = 7.80515(6) A, c = 5.52947(4) A) at room temperature. The coherent distortion is strongly suppressed in comparison with the parent LaMnO(3) phase, but the displacement ellipsoids suggest that incoherent distortions are significant and arise from local Jahn--Teller distortions. The preparation of the new phase Nd(2)GaMnO(6) has been found to depend on sample cooling rates, with detailed characterization necessary to ensure phase separation has been avoided. This compound also adopts the GdFeO(3)-type orthorhombically distorted perovskite structure (space group Pnma, a = 5.64876(1) A, b = 7.65212(2) A, c = 5.41943(1) A at room temperature). However, the B site substitution has a totally different effect on the Jahn--Teller distortion at the Mn(3+) centers. This phase exhibits a Q(2) mode Jahn--Teller distortion similar to that observed in LaMnO(3), although reduced in magnitude as a result of the introduction of Ga(3+) onto the B site. There is no evidence of a dynamic Jahn-Teller distortion. At 5 K a ferromagnetically ordered Nd(3+) moment of 1.06(6) mu(B) is aligned along the y-axis and a moment of 2.8(1) mu(B) per Mn(3+) is ordered in the xy plane making an angle of 29(2) degrees with the y-axis. The Mn(3+) moments couple ferromagnetically in the xz plane. However, along the y-axis the moments couple ferromagnetically while the x components are coupled antiferromagnetically. This results in a canted antiferromagnetic arrangement in which the dominant exchange is ferromagnetic. Nd(2)GaMnO(6) is paramagnetic above 40(5) K, with a paramagnetic moment and Weiss constant of 6.70(2) mu(B) and 45.9(4) K, respectively. An ordered moment of 6.08(3) mu(B) per Nd(2)GaMnO(6) formula unit was measured by magnetometry at 5 K in an applied magnetic field of 5 T.
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Affiliation(s)
- E J Cussen
- Department of Chemistry, University of Liverpool, Liverpool L69 7ZD, UK
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Harrison N, Bogaerts R, Reinders PH, Singleton J, Blundell SJ, Herlach F. Numerical model of quantum oscillations in quasi-two-dimensional organic metals in high magnetic fields. Phys Rev B Condens Matter 1996; 54:9977-9987. [PMID: 9984734 DOI: 10.1103/physrevb.54.9977] [Citation(s) in RCA: 110] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Chow KH, Pattenden PA, Blundell SJ, Hayes W, Pratt FL, Jestädt T, Green MA, Millburn JE, Rosseinsky MJ, Hitti B, Dunsiger SR, Kiefl RF, Chen C, Chowdhury AJ. Muon-spin-relaxation studies of magnetic order in heavily doped La2-xSrxNiO4+ delta. Phys Rev B Condens Matter 1996; 53:R14725-R14728. [PMID: 9983340 DOI: 10.1103/physrevb.53.r14725] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Demishev SV, Semeno AV, Sluchanko NE, Samarin NA, Voskoboinikov IB, Glushkov VV, Singleton J, Blundell SJ, Hill SO, Hayes W, Kartsovnik MV, Kovalev AE, Kurmoo M, Day P, Kushch ND. Resonant magnetoabsorption of millimeter-wave radiation in the quasi-two-dimensional organic metals alpha -(BEDT-TTF)2MHg(SCN)4 (M=K,Tl). Phys Rev B Condens Matter 1996; 53:12794-12803. [PMID: 9982951 DOI: 10.1103/physrevb.53.12794] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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House AA, Harrison N, Blundell SJ, Deckers I, Singleton J, Herlach F, Hayes W, Perenboom JA, Kurmoo M, Day P. Oscillatory magnetoresistance in the charge-transfer salt beta "-(BEDT-TTF)2AuBr2 in magnetic fields up to 60 T: Evidence for field-induced Fermi-surface reconstruction. Phys Rev B Condens Matter 1996; 53:9127-9136. [PMID: 9982414 DOI: 10.1103/physrevb.53.9127] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Blundell SJ, Singleton J. Semiclassical description of angle-dependent magnetoresistance oscillations in quasi-one-dimensional metals. Phys Rev B Condens Matter 1996; 53:5609-5619. [PMID: 9984169 DOI: 10.1103/physrevb.53.5609] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Cooke DW, Smith JL, Blundell SJ, Chow KH, Pattenden PA, Pratt FL, Cox SF, Brown SR, Morrobel-Sosa A, Lichti RL, Gupta LC, Nagarajan R, Hossain Z, Mazumdar C, Godart C. Competition between magnetism and superconductivity in TmNi2B2C observed by muon-spin rotation. Phys Rev B Condens Matter 1995; 52:R3864-R3867. [PMID: 9981613 DOI: 10.1103/physrevb.52.r3864] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Caulfield J, Blundell SJ, Hendriks PT, Singleton J, Doporto M, Pratt FL, House A, Perenboom JA, Hayes W, Kurmoo M, Day P. High-field magnetoresistance oscillations in alpha -. Phys Rev B Condens Matter 1995; 51:8325-8336. [PMID: 9977442 DOI: 10.1103/physrevb.51.8325] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Blundell SJ, Gester M, Bland JA, Lauter HJ, Pasyuk VV, Petrenko AV. Spin-orientation dependence in neutron reflection from a single magnetic film. Phys Rev B Condens Matter 1995; 51:9395-9398. [PMID: 9977597 DOI: 10.1103/physrevb.51.9395] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Blundell SJ, Bland JA. Polarized neutron reflection as a probe of magnetic films and multilayers. Phys Rev B Condens Matter 1992; 46:3391-3400. [PMID: 10004054 DOI: 10.1103/physrevb.46.3391] [Citation(s) in RCA: 77] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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