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Gupta A, Hillier AD, Telling MTF, Srivastava SK. Local magnetic behaviour of highly disordered undoped and Co-doped Bi2Se3 nanoplates: a muon spin relaxation study. Nanotechnology 2022; 33:215701. [PMID: 35130523 DOI: 10.1088/1361-6528/ac5285] [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: 11/19/2021] [Accepted: 02/07/2022] [Indexed: 06/14/2023]
Abstract
Magnetism induced by defects in nominally non-magnetic solids has attracted intense scientific interest in recent years. The local magnetism in highly disordered undoped and Co-doped topological insulator (TI) Bi2Se3nanoplates has been investigated by muon spin relaxation (μSR). UsingμSR spectroscopy, together with other macroscopic characterizations, we find that these nanoplates are composed of a core with both static fields and dynamically fluctuating moments, and a shell with purely dynamically fluctuating moments. The fluctuations in the core die out at low temperatures, while those in the shell continue till 2 K. When Bi2Se3is doped with Co, the static magnetic component increases, whilst keeping the dual (static-plus-dynamic) nature intact. The findings indicate that highly disordered TI's could constitute a new class of promising magnetic materials that can be engineered by magnetic impurity doping.
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Affiliation(s)
- Anu Gupta
- Department of Physics, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
| | - A D Hillier
- ISIS Neutron and Muon Facility, STFC Rutherford Appleton Laboratory, Chilton, Didcot OX11 0QX, United Kingdom
| | - M T F Telling
- ISIS Neutron and Muon Facility, STFC Rutherford Appleton Laboratory, Chilton, Didcot OX11 0QX, United Kingdom
| | - S K Srivastava
- Department of Physics, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
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2
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Shimura Y, Wörl A, Sundermann M, Tsuda S, Adroja DT, Bhattacharyya A, Strydom AM, Hillier AD, Pratt FL, Gloskovskii A, Severing A, Onimaru T, Gegenwart P, Takabatake T. Antiferromagnetic Correlations in Strongly Valence Fluctuating CeIrSn. Phys Rev Lett 2021; 126:217202. [PMID: 34114835 DOI: 10.1103/physrevlett.126.217202] [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: 10/08/2020] [Accepted: 04/29/2021] [Indexed: 06/12/2023]
Abstract
CeIrSn with a quasikagome Ce lattice in the hexagonal basal plane is a strongly valence fluctuating compound, as we confirm by hard x-ray photoelectron spectroscopy and inelastic neutron scattering, with a high Kondo temperature of T_{K}∼480 K. We report a negative in-plane thermal expansion α/T below 2 K, which passes through a broad minimum near 0.75 K. Volume and a-axis magnetostriction for B∥a are markedly negative at low fields and change sign before a sharp metamagnetic anomaly at 6 T. These behaviors are unexpected for Ce-based intermediate valence systems, which should feature positive expansivity. Rather they point towards antiferromagnetic correlations at very low temperatures. This is supported by muon spin relaxation measurements down to 0.1 K, which provide microscopic evidence for a broad distribution of internal magnetic fields. Comparison with isostructural CeRhSn suggests that these antiferromagnetic correlations emerging at T≪T_{K} result from geometrical frustration.
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Affiliation(s)
- Y Shimura
- Graduate School of Advanced Science and Engineering, Hiroshima University, Higashi-Hiroshima 739-8530, Japan
| | - A Wörl
- Experimental Physics VI, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany
| | - M Sundermann
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
- Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg, Germany
| | - S Tsuda
- Graduate School of Advanced Science and Engineering, Hiroshima University, Higashi-Hiroshima 739-8530, Japan
| | - D T Adroja
- ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot Oxon OX11 0QX, United Kingdom
- Highly Correlated Matter Research Group, Physics Department, University of Johannesburg, PO Box 524, Auckland Park 2006, South Africa
| | - A Bhattacharyya
- Department of Physics, Ramakrishna Mission Vivekananda Educational and Research Institute, Belur Math, Howrah 711202, West Bengal, India
| | - A M Strydom
- Highly Correlated Matter Research Group, Physics Department, University of Johannesburg, PO Box 524, Auckland Park 2006, South Africa
| | - A D Hillier
- ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot Oxon OX11 0QX, United Kingdom
| | - F L Pratt
- ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot Oxon OX11 0QX, United Kingdom
| | - A Gloskovskii
- Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg, Germany
| | - A Severing
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
- Institute of Physics II, University of Cologne, 50937 Cologne, Germany
| | - T Onimaru
- Graduate School of Advanced Science and Engineering, Hiroshima University, Higashi-Hiroshima 739-8530, Japan
| | - P Gegenwart
- Experimental Physics VI, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany
| | - T Takabatake
- Graduate School of Advanced Science and Engineering, Hiroshima University, Higashi-Hiroshima 739-8530, Japan
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3
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Biswas PK, Ghosh SK, Zhao JZ, Mayoh DA, Zhigadlo ND, Xu X, Baines C, Hillier AD, Balakrishnan G, Lees MR. Chiral singlet superconductivity in the weakly correlated metal LaPt 3P. Nat Commun 2021; 12:2504. [PMID: 33947862 PMCID: PMC8097077 DOI: 10.1038/s41467-021-22807-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [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: 12/10/2020] [Accepted: 03/30/2021] [Indexed: 11/09/2022] Open
Abstract
Chiral superconductors are novel topological materials with finite angular momentum Cooper pairs circulating around a unique chiral axis, thereby spontaneously breaking time-reversal symmetry. They are rather scarce and usually feature triplet pairing: a canonical example is the chiral p-wave state realized in the A-phase of superfluid He3. Chiral triplet superconductors are, however, topologically fragile with the corresponding gapless boundary modes only weakly protected against symmetry-preserving perturbations in contrast to their singlet counterparts. Using muon spin relaxation measurements, here we report that the weakly correlated pnictide compound LaPt3P has the two key features of a chiral superconductor: spontaneous magnetic fields inside the superconducting state indicating broken time-reversal symmetry and low temperature linear behaviour in the superfluid density indicating line nodes in the order parameter. Using symmetry analysis, first principles band structure calculation and mean-field theory, we unambiguously establish that the superconducting ground state of LaPt3P is a chiral d-wave singlet.
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Affiliation(s)
- P K Biswas
- ISIS Pulsed Neutron and Muon Source, STFC Rutherford Appleton Laboratory, Harwell Campus, Didcot, Oxfordshire, UK.
| | - S K Ghosh
- School of Physical Sciences, University of Kent, Canterbury, UK.
| | - J Z Zhao
- Co-Innovation Center for New Energetic Materials, Southwest University of Science and Technology, Mianyang, China
| | - D A Mayoh
- Physics Department, University of Warwick, Coventry, UK
| | - N D Zhigadlo
- Laboratory for Solid State Physics, ETH Zurich, Zurich, Switzerland.,CrystMat Company, Zurich, Switzerland
| | - Xiaofeng Xu
- Department of Applied Physics, Zhejiang University of Technology, Hangzhou, China
| | - C Baines
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, Villigen PSI, Switzerland
| | - A D Hillier
- ISIS Pulsed Neutron and Muon Source, STFC Rutherford Appleton Laboratory, Harwell Campus, Didcot, Oxfordshire, UK
| | | | - M R Lees
- Physics Department, University of Warwick, Coventry, UK
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4
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Tula T, Möller G, Quintanilla J, Giblin SR, Hillier AD, McCabe EE, Ramos S, Barker DS, Gibson S. Machine learning approach to muon spectroscopy analysis. J Phys Condens Matter 2021; 33:194002. [PMID: 33545697 DOI: 10.1088/1361-648x/abe39e] [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: 11/20/2020] [Accepted: 02/05/2021] [Indexed: 06/12/2023]
Abstract
In recent years, artificial intelligence techniques have proved to be very successful when applied to problems in physical sciences. Here we apply an unsupervised machine learning (ML) algorithm called principal component analysis (PCA) as a tool to analyse the data from muon spectroscopy experiments. Specifically, we apply the ML technique to detect phase transitions in various materials. The measured quantity in muon spectroscopy is an asymmetry function, which may hold information about the distribution of the intrinsic magnetic field in combination with the dynamics of the sample. Sharp changes of shape of asymmetry functions-measured at different temperatures-might indicate a phase transition. Existing methods of processing the muon spectroscopy data are based on regression analysis, but choosing the right fitting function requires knowledge about the underlying physics of the probed material. Conversely, PCA focuses on small differences in the asymmetry curves and works without any prior assumptions about the studied samples. We discovered that the PCA method works well in detecting phase transitions in muon spectroscopy experiments and can serve as an alternative to current analysis, especially if the physics of the studied material are not entirely known. Additionally, we found out that our ML technique seems to work best with large numbers of measurements, regardless of whether the algorithm takes data only for a single material or whether the analysis is performed simultaneously for many materials with different physical properties.
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Affiliation(s)
- T Tula
- School of Physical Sciences, University of Kent, Park Wood Rd, Canterbury CT2 7NH, United Kingdom
| | - G Möller
- School of Physical Sciences, University of Kent, Park Wood Rd, Canterbury CT2 7NH, United Kingdom
| | - J Quintanilla
- School of Physical Sciences, University of Kent, Park Wood Rd, Canterbury CT2 7NH, United Kingdom
| | - S R Giblin
- School of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA, United Kingdom
| | - A D Hillier
- ISIS Facility, STFC Rutherford Appleton Laboratory, Chilton, Didcot Oxon, OX11 0QX, United Kingdom
| | - E E McCabe
- School of Physical Sciences, University of Kent, Park Wood Rd, Canterbury CT2 7NH, United Kingdom
| | - S Ramos
- School of Physical Sciences, University of Kent, Park Wood Rd, Canterbury CT2 7NH, United Kingdom
| | - D S Barker
- School of Physical Sciences, University of Kent, Park Wood Rd, Canterbury CT2 7NH, United Kingdom
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, United Kingdom
| | - S Gibson
- School of Physical Sciences, University of Kent, Park Wood Rd, Canterbury CT2 7NH, United Kingdom
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Bhattacharyya A, Panda K, Adroja DT, Kase N, Biswas PK, Saha S, Das T, Lees MR, Hillier AD. Investigation of superconducting gap structure in HfIrSi using muon spin relaxation/rotation. J Phys Condens Matter 2020; 32:085601. [PMID: 31689696 DOI: 10.1088/1361-648x/ab549e] [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: 06/10/2023]
Abstract
We have investigated the superconducting state of HfIrSi using magnetization, specific heat, muon spin rotation and relaxation ([Formula: see text]SR) measurements. Superconductivity was observed at [Formula: see text] K in both specific heat and magnetization measurements. From an analysis of the transverse-field [Formula: see text]SR data, it is clear that the temperature variation of superfluid density is well fitted by an isotropic Bardeen-Cooper-Schrieffer (BCS) type s-wave gap structure. The superconducting carrier density [Formula: see text] m-3, the magnetic penetration depth, [Formula: see text] nm, and the effective mass, [Formula: see text], were calculated from the TF-[Formula: see text]SR data. Zero-field [Formula: see text]SR data for HfIrSi reveal the absence of any spontaneous magnetic moments below [Formula: see text], indicating that time-reversal symmetry (TRS) is preserved in the superconducting state of HfIrSi. Theoretical investigations suggest that the Hf and Ir atoms hybridize strongly along the c-axis, and that this is responsible for the strong three-dimensionality of this system which screens the Coulomb interaction. As a result, despite the presence of d-electrons in HfIrSi, these correlation effects are weakened, making the electron-phonon coupling more important.
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Affiliation(s)
- A Bhattacharyya
- Department of Physics, Ramakrishna Mission Vivekananda Educational and Research Institute, Howrah 711202, West Bengal, India
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6
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Bhattacharyya A, Adroja DT, Biswas PK, Sato YJ, Lees MR, Aoki D, Hillier AD. Ir 5d-band derived superconductivity in LaIr 3. J Phys Condens Matter 2020; 32:065602. [PMID: 31509814 DOI: 10.1088/1361-648x/ab4389] [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: 06/10/2023]
Abstract
The superconducting properties of rhombohedral LaIr3 were examined using susceptibility, resistivity, heat capacity, and zero-field (ZF) and transverse-field (TF) muon spin relaxation and rotation ([Formula: see text]SR) measurements. The susceptibility and resistivity measurements confirm a superconducting transition below [Formula: see text] K. Two successive transitions are observed in the heat capacity data, one at [Formula: see text] K and a second at 1.2 K below [Formula: see text]. The heat capacity jump is [Formula: see text], which is lower than 1.43 expected for Bardeen-Cooper-Schrieffer (BCS) weak-coupling limit. TF-[Formula: see text]SR measurements reveal a fully gapped s-wave superconductivity with [Formula: see text], which is small compared to the BCS value of 3.56, suggesting weak-coupling superconductivity. The magnetic penetration depth, [Formula: see text], estimated from TF-[Formula: see text]SR gives [Formula: see text] nm, a superconducting carrier density [Formula: see text] carriers m-3 and a carrier effective-mass enhancement factor [Formula: see text]. ZF-[Formula: see text]SR data show no evidence for any spontaneous magnetic fields below [Formula: see text], which demonstrates that time-reversal symmetry is preserved in the superconducting state of LaIr3.
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Affiliation(s)
- A Bhattacharyya
- Department of Physics, Ramakrishna Mission Vivekananda Educational and Research Institute, Belur Math, Howrah 711202, West Bengal, India
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7
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Singh D, Sajilesh KP, Marik S, Biswas PK, Hillier AD, Singh RP. Nodeless s-wave superconductivity in the [Formula: see text]-Mn structure type noncentrosymmetric superconductor TaOs: a [Formula: see text]SR study. J Phys Condens Matter 2020; 32:015602. [PMID: 31509816 DOI: 10.1088/1361-648x/ab43a4] [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: 06/10/2023]
Abstract
Noncentrosymmetric superconductors can lead to a variety of exotic properties in the superconducting state such as line nodes, multigap behavior, and time-reversal symmetry breaking. In this paper, we report the properties of a new noncentrosymmetric superconductor TaOs, using muon spin relaxation and rotation measurements. It is shown using the zero-field muon experiment that TaOs preserve the time-reversal symmetry in the superconducting state. From the transverse field muon measurements, we extract the temperature dependence of [Formula: see text], which is proportional to the superfluid density. This data can be fit with a fully gapped s-wave model for [Formula: see text] = 2.01 [Formula: see text] 0.02. Furthermore, the value of magnetic penetration depth is found to be 5919 [Formula: see text] 45 [Formula: see text], which is consistent with the value obtained from the bulk measurements.
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Affiliation(s)
- D Singh
- Indian Institute of Science Education and Research Bhopal, Bhopal, 462066, India
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8
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Mayoh DA, Pearce MJ, Götze K, Hillier AD, Balakrishnan G, Lees MR. Superconductivity and the upper critical field in the chiral noncentrosymmetric superconductor NbRh 2B 2. J Phys Condens Matter 2019; 31:465601. [PMID: 31425149 DOI: 10.1088/1361-648x/ab348b] [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: 06/10/2023]
Abstract
NbRh2B2 crystallises in a chiral noncentrosymmetric structure and exhibits bulk type-II superconductivity below [Formula: see text] K. Here we show that the temperature dependence of the upper critical field deviates from the behaviour expected for both Werthamer-Helfand-Hohenberg and the Ginzburg-Landau models and that [Formula: see text] T exceeds the Pauli paramagnetic limit, [Formula: see text] T. We explore the reasons for this enhancement. Transverse-field muon spectroscopy measurements suggest that the superconducting gap is either s-wave or [Formula: see text]-wave, and the pressure dependence of [Formula: see text] reveals the superconducting gap is primarily s-wave in character. The magnetic penetration depth [Formula: see text] nm. Heat capacity measurements reveal the presence of a multigap [Formula: see text]-wave superconducting order parameter and moderate electron-phonon coupling.
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Affiliation(s)
- D A Mayoh
- Physics Department, University of Warwick, Coventry, CV4 7AL, United Kingdom
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9
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Bhattacharyya A, Adroja DT, Panda K, Saha S, Das T, Machado AJS, Cigarroa OV, Grant TW, Fisk Z, Hillier AD, Manfrinetti P. Evidence of a Nodal Line in the Superconducting Gap Symmetry of Noncentrosymmetric ThCoC_{2}. Phys Rev Lett 2019; 122:147001. [PMID: 31050469 DOI: 10.1103/physrevlett.122.147001] [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: 10/14/2018] [Revised: 01/14/2019] [Indexed: 06/09/2023]
Abstract
The newly discovered noncentrosymmetric superconductor ThCoC_{2} exhibits numerous types of unconventional behavior in the field dependent heat capacity data. Here we present the first measurement of the gap symmetry of ThCoC_{2} by muon spin rotation and relaxation (μSR) measurements. The temperature dependence of the magnetic penetration depth measured using the transverse field μSR experiment reveals the evidence of a nodal pairing symmetry. To understand this finding, we carry out calculations of the superconducting pairing eigenvalue and eigenfunction (pairing symmetry) due to the spin-fluctuation mechanism by directly implementing the ab initio band structures. We find that the system possesses a single Fermi surface with considerable three dimensionality and a strong nesting along the k_{z} direction. Such nesting promotes a superconducting state with a cosk_{z}-like pairing symmetry with a prominent nodal line on the k_{z}=±π/2 plane. The result agrees well with the experimental data.
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Affiliation(s)
- A Bhattacharyya
- Department of Physics, Ramakrishna Mission Vivekananda Educational and Research Institute, Belur Math, Howrah 711202, West Bengal, India
- ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot Oxon, OX11 0QX, United Kingdom
- Highly Correlated Matter Research Group, Physics Department, University of Johannesburg, P. O. Box 524, Auckland Park 2006, South Africa
| | - D T Adroja
- ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot Oxon, OX11 0QX, United Kingdom
- Highly Correlated Matter Research Group, Physics Department, University of Johannesburg, P. O. Box 524, Auckland Park 2006, South Africa
| | - K Panda
- Department of Physics, Ramakrishna Mission Vivekananda Educational and Research Institute, Belur Math, Howrah 711202, West Bengal, India
| | - Surabhi Saha
- Department of Physics, Indian Institute of Science, Bangalore 560012, India
| | - Tanmoy Das
- Department of Physics, Indian Institute of Science, Bangalore 560012, India
| | - A J S Machado
- Escola de Engenharia de Lorena, Universidade de São Paulo, P. O. Box 116, Lorena, São Paulo, 12602810
| | - O V Cigarroa
- Escola de Engenharia de Lorena, Universidade de São Paulo, P. O. Box 116, Lorena, São Paulo, 12602810
- Department of Physics and Astronomy, University of California-Irvine, Irvine, California 92697, USA
| | - T W Grant
- Escola de Engenharia de Lorena, Universidade de São Paulo, P. O. Box 116, Lorena, São Paulo, 12602810
- Department of Physics and Astronomy, University of California-Irvine, Irvine, California 92697, USA
| | - Z Fisk
- Department of Physics and Astronomy, University of California-Irvine, Irvine, California 92697, USA
| | - A D Hillier
- ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot Oxon, OX11 0QX, United Kingdom
| | - P Manfrinetti
- Department of Chemistry, University of Genova, 16146 Genova, Italy
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10
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Shang T, Smidman M, Ghosh SK, Baines C, Chang LJ, Gawryluk DJ, Barker JAT, Singh RP, Paul DM, Balakrishnan G, Pomjakushina E, Shi M, Medarde M, Hillier AD, Yuan HQ, Quintanilla J, Mesot J, Shiroka T. Time-Reversal Symmetry Breaking in Re-Based Superconductors. Phys Rev Lett 2018; 121:257002. [PMID: 30608781 DOI: 10.1103/physrevlett.121.257002] [Citation(s) in RCA: 2] [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: 03/11/2018] [Revised: 07/30/2018] [Indexed: 06/09/2023]
Abstract
To trace the origin of time-reversal symmetry breaking (TRSB) in Re-based superconductors, we performed comparative muon-spin rotation and relaxation (μSR) studies of superconducting noncentrosymmetric Re_{0.82}Nb_{0.18} (T_{c}=8.8 K) and centrosymmetric Re (T_{c}=2.7 K). In Re_{0.82}Nb_{0.18}, the low-temperature superfluid density and the electronic specific heat evidence a fully gapped superconducting state, whose enhanced gap magnitude and specific-heat discontinuity suggest a moderately strong electron-phonon coupling. In both Re_{0.82}Nb_{0.18} and pure Re, the spontaneous magnetic fields revealed by zero-field μSR below T_{c} indicate time-reversal symmetry breaking and thus unconventional superconductivity. The concomitant occurrence of TRSB in centrosymmetric Re and noncentrosymmetric ReT (T=transition metal), yet its preservation in the isostructural noncentrosymmetric superconductors Mg_{10}Ir_{19}B_{16} and Nb_{0.5}Os_{0.5}, strongly suggests that the local electronic structure of Re is crucial for understanding the TRSB superconducting state in Re and ReT. We discuss the superconducting order parameter symmetries that are compatible with the experimental observations.
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Affiliation(s)
- T Shang
- Laboratory for Multiscale Materials Experiments, Paul Scherrer Institut, Villigen CH-5232, Switzerland
- Swiss Light Source, Paul Scherrer Institut, Villigen CH-5232, Switzerland
- Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne CH-1015, Switzerland
| | - M Smidman
- Center for Correlated Matter and Department of Physics, Zhejiang University, Hangzhou 310058, China
| | - S K Ghosh
- School of Physical Sciences, University of Kent, Canterbury CT2 7NH, United Kingdom
| | - C Baines
- Laboratory for Muon-Spin Spectroscopy, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - L J Chang
- Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan
| | - D J Gawryluk
- Laboratory for Multiscale Materials Experiments, Paul Scherrer Institut, Villigen CH-5232, Switzerland
| | - J A T Barker
- Laboratory for Muon-Spin Spectroscopy, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - R P Singh
- Indian Institute of Science Education and Research Bhopal, Bhopal, 462066, India
| | - D McK Paul
- Physics Department, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - G Balakrishnan
- Physics Department, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - E Pomjakushina
- Laboratory for Multiscale Materials Experiments, Paul Scherrer Institut, Villigen CH-5232, Switzerland
| | - M Shi
- Swiss Light Source, Paul Scherrer Institut, Villigen CH-5232, Switzerland
| | - M Medarde
- Laboratory for Multiscale Materials Experiments, Paul Scherrer Institut, Villigen CH-5232, Switzerland
| | - A D Hillier
- ISIS Facility, STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Oxfordshire, OX11 0QX, United Kingdom
| | - H Q Yuan
- Center for Correlated Matter and Department of Physics, Zhejiang University, Hangzhou 310058, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing Univeristy, Nanjing 210093, China
| | - J Quintanilla
- School of Physical Sciences, University of Kent, Canterbury CT2 7NH, United Kingdom
| | - J Mesot
- Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne CH-1015, Switzerland
- Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
- Laboratorium für Festkörperphysik, ETH Zürich, CH-8093 Zurich, Switzerland
| | - T Shiroka
- Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
- Laboratorium für Festkörperphysik, ETH Zürich, CH-8093 Zurich, Switzerland
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Abstract
For the last 30 years, muon experiments at ISIS pulsed neutron and muon facility at the Rutherford Appleton Laboratory, Oxfordshire have been making a significant contribution to a number of scientific fields. The muon facilities at ISIS consist of eight experimental areas. The European Commission Muon facility consists of three experimental areas with a fixed momentum (28 MeV c-1). The RIKEN-RAL facility has a variable momentum (17-90 MeV c-1) and a choice of negative or positive muons delivering muons to four experimental areas. There is also an area recently used for a muon ionization cooling experiment. In this paper, the ISIS pulsed muon facilities are reviewed, including the beam characteristics that could be useful for muography experiments.This article is part of the Theo Murphy meeting issue 'Cosmic-ray muography'.
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Affiliation(s)
- A D Hillier
- ISIS Pulsed Neutron and Muon Source, STFC Rutherford Appleton Laboratory, Didcot OX11 0QX, UK
| | - J S Lord
- ISIS Pulsed Neutron and Muon Source, STFC Rutherford Appleton Laboratory, Didcot OX11 0QX, UK
| | - K Ishida
- RIKEN Nishina Center, RIKEN, Wako, Saitama, Japan
| | - C Rogers
- ISIS Pulsed Neutron and Muon Source, STFC Rutherford Appleton Laboratory, Didcot OX11 0QX, UK
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12
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Brown KL, Stockdale CPJ, Luo H, Zhao X, Li JF, Viehland D, Xu G, Gehring PM, Ishida K, Hillier AD, Stock C. Depth dependant element analysis of PbMg 1/3Nb 2/3O 3 using muonic x-rays. J Phys Condens Matter 2018; 30:125703. [PMID: 29488465 DOI: 10.1088/1361-648x/aaade3] [Citation(s) in RCA: 1] [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] [Indexed: 06/08/2023]
Abstract
The relaxor PbMg1/3Nb2/3O3 (PMN) has received attention due to its potential applications as a piezoelectric when doped with PbTiO3 (PT). Previous results have found that there are two phases existing in the system, one linked to the near-surface regions of the sample, the other in the bulk. However, the exact origin of these two phases is unclear. In this paper, depth dependant analysis results from negative muon implantation experiments are presented. It is shown that the Pb content is constant throughout all depths probed in the sample, but the Mg and Nb content changes in the near-surface region below 100 μm. At an implantation depth of 60 μm, it is found that there is a 25% increase in Mg content, with a simultaneous 5% decrease in Nb content in order to maintain charge neutrality. These results show that the previously observed skin effects in PMN are due to a change in concentration and unit cell.
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Affiliation(s)
- K L Brown
- School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom
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Singh D, Barker JAT, Thamizhavel A, Hillier AD, Paul DM, Singh RP. Superconducting properties and μSR study of the noncentrosymmetric superconductor Nb 0.5Os 0.5. J Phys Condens Matter 2018; 30:075601. [PMID: 29355110 DOI: 10.1088/1361-648x/aaa376] [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
The properties of the noncentrosymmetric superconductor (α-[Formula: see text] structure) Nb0.5Os0.5 have been investigated using resistivity, magnetization, specific heat, and muon spin relaxation and rotation (μSR) measurements. These measurements suggest that Nb0.5Os0.5 is a weakly coupled ([Formula: see text]) type-II superconductor ([Formula: see text]), having a bulk superconducting transition temperature T c = 3.07 K. The specific heat data fits well with the single-gap BCS model indicating nodeless s-wave superconductivity in Nb0.5Os0.5. The μSR measurements also confirm [Formula: see text]-wave superconductivity with the preserved time-reversal symmetry.
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Affiliation(s)
- D Singh
- Indian Institute of Science Education and Research Bhopal, Bhopal, 462066, India
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14
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Bhattacharyya A, Adroja DT, Hillier AD, Jha R, Awana VPS, Strydom AM. Superconducting gap structure in the electron doped BiS 2-based superconductor. J Phys Condens Matter 2017; 29:265602. [PMID: 28555613 DOI: 10.1088/1361-648x/aa7189] [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
The influence of electron doping on semimetallic SrFBiS2 has been investigated by means of resistivity, zero and transverse - field (ZF/TF) muon spin relaxation/rotation (μSR) experiments. SrFBiS2 is semimetallic in its normal state and small amounts of La doping results in bulk superconductivity at 2.8 K, at ambient pressure. The temperature dependence of the superfluid density as determined by TF-μSR can be best modelled by an isotropic s - wave type superconducting gap. We have estimated the magnetic penetration depth [Formula: see text] nm, superconducting carrier density [Formula: see text] carriers m-3 and effective-mass enhancement m * = 1.558 m e. Additionally, there is no clear sign of the occurrence of spontaneous internal magnetic fields below [Formula: see text], which implies that the superconducting state in this material can not be categorized by the broken time-reversal symmetry which is in agreement with the previous theoretical prediction.
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Affiliation(s)
- A Bhattacharyya
- ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot Oxon, OX11 0QX, United Kingdom. Highly Correlated Matter Research Group, Physics Department, University of Johannesburg, PO Box 524, Auckland Park 2006, South Africa. Department of Physics, Ramakrishna Mission Vivekananda University, Belur Math, Howrah 711202, West Bengal, India
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15
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Yokoyama K, Lord JS, Murahari P, Wang K, Dunstan DJ, Waller SP, McPhail DJ, Hillier AD, Henson J, Harper MR, Heathcote P, Drew AJ. The new high field photoexcitation muon spectrometer at the ISIS pulsed neutron and muon source. Rev Sci Instrum 2016; 87:125111. [PMID: 28040964 DOI: 10.1063/1.4972827] [Citation(s) in RCA: 3] [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: 06/06/2023]
Abstract
A high power pulsed laser system has been installed on the high magnetic field muon spectrometer (HiFi) at the International Science Information Service pulsed neutron and muon source, situated at the STFC Rutherford Appleton Laboratory in the UK. The upgrade enables one to perform light-pump muon-probe experiments under a high magnetic field, which opens new applications of muon spin spectroscopy. In this report we give an overview of the principle of the HiFi laser system and describe the newly developed techniques and devices that enable precisely controlled photoexcitation of samples in the muon instrument. A demonstration experiment illustrates the potential of this unique combination of the photoexcited system and avoided level crossing technique.
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Affiliation(s)
- K Yokoyama
- School of Physics and Astronomy, Queen Mary University of London, Mile End, London E1 4NS, United Kingdom
| | - J S Lord
- ISIS, STFC Rutherford Appleton Laboratory, Didcot OX11 0QX, United Kingdom
| | - P Murahari
- School of Physics and Astronomy, Queen Mary University of London, Mile End, London E1 4NS, United Kingdom
| | - K Wang
- School of Physics and Astronomy, Queen Mary University of London, Mile End, London E1 4NS, United Kingdom
| | - D J Dunstan
- School of Physics and Astronomy, Queen Mary University of London, Mile End, London E1 4NS, United Kingdom
| | - S P Waller
- ISIS, STFC Rutherford Appleton Laboratory, Didcot OX11 0QX, United Kingdom
| | - D J McPhail
- ISIS, STFC Rutherford Appleton Laboratory, Didcot OX11 0QX, United Kingdom
| | - A D Hillier
- ISIS, STFC Rutherford Appleton Laboratory, Didcot OX11 0QX, United Kingdom
| | - J Henson
- Litron Lasers Ltd., Rugby CV21 1PB, United Kingdom
| | - M R Harper
- Litron Lasers Ltd., Rugby CV21 1PB, United Kingdom
| | - P Heathcote
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End, London E1 4NS, United Kingdom
| | - A J Drew
- School of Physics and Astronomy, Queen Mary University of London, Mile End, London E1 4NS, United Kingdom
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Barker JAT, Singh D, Thamizhavel A, Hillier AD, Lees MR, Balakrishnan G, Paul DM, Singh RP. Unconventional Superconductivity in La(7)Ir(3) Revealed by Muon Spin Relaxation: Introducing a New Family of Noncentrosymmetric Superconductor That Breaks Time-Reversal Symmetry. Phys Rev Lett 2015; 115:267001. [PMID: 26765016 DOI: 10.1103/physrevlett.115.267001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Indexed: 06/05/2023]
Abstract
The superconductivity of the noncentrosymmetric compound La(7)Ir(3) is investigated using muon spin rotation and relaxation. Zero-field measurements reveal the presence of spontaneous static or quasistatic magnetic fields below the superconducting transition temperature T(c)=2.25 K-a clear indication that the superconducting state breaks time-reversal symmetry. Furthermore, transverse-field rotation measurements suggest that the superconducting gap is isotropic and that the pairing symmetry of the superconducting electrons is predominantly s wave with an enhanced binding strength. The results indicate that the superconductivity in La(7)Ir(3) may be unconventional and paves the way for further studies of this family of materials.
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Affiliation(s)
- J A T Barker
- Physics Department, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - D Singh
- Department of Physics, Indian Institute of Science Education and Research Bhopal, Bhopal 462066, India
| | - A Thamizhavel
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Mumbai 400005, India
| | - A D Hillier
- ISIS facility, STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Oxfordshire OX11 0QX, United Kingdom
| | - M R Lees
- Physics Department, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - G Balakrishnan
- Physics Department, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - D McK Paul
- Physics Department, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - R P Singh
- Department of Physics, Indian Institute of Science Education and Research Bhopal, Bhopal 462066, India
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Das D, Bhattacharyya A, Anand VK, Hillier AD, Taylor JW, Gruner T, Geibel C, Adroja DT, Hossain Z. Muon spin relaxation study on itinerant ferromagnet CeCrGe₃ and the effect of Ti substitution on magnetism of CeCrGe₃. J Phys Condens Matter 2015; 27:016004. [PMID: 25493957 DOI: 10.1088/0953-8984/27/1/016004] [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
A Muon spin relaxation (µSR) study has been performed on the Kondo lattice heavy fermion itinerant ferromagnet CeCrGe3. Recent investigations of bulk properties have revealed a long-range ordering of Cr moments at Tc = 70 K in this compound. Our µSR investigation between 1.2 K and 125 K confirm the bulk magnetic order which is marked by a loss in initial asymmetry below 70 K accompanied with a sharp increase in the muon depolarization rate. Field dependent µSR spectra show that the internal field at the muon site is higher than 0.25 T apparently due to the ferromagnetic nature of ordering. The effect of Ti substitution on the magnetism in CeCrGe3 is presented. A systematic study has been made on polycrystalline CeCr(1-x)Ti(x)Ge3 (0 ⩽ x ⩽ 1) using magnetic susceptibility χ(T), isothermal magnetization M(H), specific heat C(T) and electrical resistivity ρ(T) measurements which clearly reveal that the substitution of Ti for Cr in CeCrGe3 strongly influences the exchange interaction and ferromagnetic ordering of Cr moments. The Cr moment ordering temperature is suppressed gradually with increasing Ti concentration up to x = 0.50 showing Tc = 7 K beyond which Ce moment ordering starts to dominate and a crossover between Cr and Ce moment ordering is observed with a Ce moment ordering Tc = 14 K for x = 1.0. The Kondo lattice behavior is evident from temperature dependence of ρ(T) in all CeCr(1-x)Ti(x)Ge3 samples.
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Affiliation(s)
- Debarchan Das
- Department of Physics, Indian Institute of Technology, Kanpur 208016, India
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18
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Anand VK, Adroja DT, Bhattacharyya A, Hillier AD, Taylor JW, Strydom AM. Investigations of the singlet ground state system: PrIrSi3. J Phys Condens Matter 2014; 26:306001. [PMID: 24994692 DOI: 10.1088/0953-8984/26/30/306001] [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: 06/03/2023]
Abstract
We report our comprehensive study of physical properties of a ternary intermetallic compound PrIrSi3 investigated by dc magnetic susceptibility χ(T), isothermal magnetization M(H), thermo-remnant magnetization M(t), ac magnetic susceptibility χac(T), specific heat Cp(T), electrical resistivity ρ(T), muon spin relaxation (µSR) and inelastic neutron scattering (INS) measurements. A magnetic phase transition is marked by a sharp anomaly at Ttr = 12.2 K in χ(T) measured at low applied fields which is also reflected in the Cp(T) data through a weak anomaly at 12 K. An irreversibility between the zero field cooled and field cooled χ(T) data below 12.2 K and a very large relaxation time of M(t) indicates the presence of ferromagnetic correlation. The magnetic part of specific heat shows a broad Schottky-type anomaly near 40 K due to the crystal electric field (CEF) effect. An extremely small value of magnetic entropy below 12 K suggests a CEF-split singlet ground state which is confirmed from our analysis of INS data. The INS spectra show two prominent inelastic excitations at 8.5 meV and 18.5 meV that could be well accounted by a CEF model. The CEF splitting energy between the ground state singlet and the first excited doublet is found to be 92 K. Our µSR data reveal a possible magnetic ordering below 30 K, which is much higher than that found from the specific heat and magnetic susceptibility measurements. This could be due to the presence of short range correlations well above the long range magnetic ordering or due to the electronic changes induced by muons. The induced moment magnetism in the singlet ground state system PrIrSi3 with such a large splitting energy of 92 K is quite surprising.
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Affiliation(s)
- V K Anand
- ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, OX11 0QX, UK. Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner Platz 1, D-14109 Berlin, Germany
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19
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Singh RP, Hillier AD, Mazidian B, Quintanilla J, Annett JF, Paul DM, Balakrishnan G, Lees MR. Detection of time-reversal symmetry breaking in the noncentrosymmetric superconductor Re6Zr using muon-spin spectroscopy. Phys Rev Lett 2014; 112:107002. [PMID: 24679322 DOI: 10.1103/physrevlett.112.107002] [Citation(s) in RCA: 7] [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: 07/03/2013] [Indexed: 06/03/2023]
Abstract
We have investigated the superconducting state of the noncentrosymmetric compound Re6Zr using magnetization, heat capacity, and muon-spin relaxation or rotation (μSR) measurements. Re6Zr has a superconducting transition temperature, Tc=6.75±0.05 K. Transverse-field μSR experiments, used to probe the superfluid density, suggest an s-wave character for the superconducting gap. However, zero and longitudinal-field μSR data reveal the presence of spontaneous static magnetic fields below Tc indicating that time-reversal symmetry is broken in the superconducting state and an unconventional pairing mechanism. An analysis of the pairing symmetries identifies the ground states compatible with time-reversal symmetry breaking.
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Affiliation(s)
- R P Singh
- Physics Department, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - A D Hillier
- ISIS facility, STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Oxfordshire OX11 0QX, United Kingdom
| | - B Mazidian
- ISIS facility, STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Oxfordshire OX11 0QX, United Kingdom and H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, United Kingdom
| | - J Quintanilla
- ISIS facility, STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Oxfordshire OX11 0QX, United Kingdom and SEPnet and Hubbard Theory Consortium, School of Physical Sciences, University of Kent, Canterbury CT2 7NH, United Kingdom
| | - J F Annett
- H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, United Kingdom
| | - D McK Paul
- Physics Department, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - G Balakrishnan
- Physics Department, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - M R Lees
- Physics Department, University of Warwick, Coventry CV4 7AL, United Kingdom
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20
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Anand VK, Adroja DT, Hillier AD. Magnetic and transport properties of PrRhSi3. J Phys Condens Matter 2013; 25:196003. [PMID: 23604428 DOI: 10.1088/0953-8984/25/19/196003] [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] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We have investigated the magnetic and transport properties of a noncentrosymmetric compound PrRhSi3 by dc magnetic susceptibility χ(T), isothermal magnetization M(H), thermoremanent magnetization M(t), specific heat Cp(T), electrical resistivity ρ(T,H) and muon spin relaxation (μSR) measurements. At low fields χ(T) shows two anomalies near 15 and 7 K with an irreversibility between ZFC and FC data below 15 K. In contrast, no anomaly is observed in Cp(T) or ρ(T) data. M(H) data at 2 K exhibit very sharp increase below 0.5 T and a weak hysteresis. M(t) exhibits very slow relaxation, typical for a spin-glass system. Even though the absence of any anomaly in Cp(T) is consistent with the spin-glass type behavior, there is no obvious origin of spin-glass behavior in this structurally well ordered compound. The crystal electric field (CEF) analysis of Cp(T) data indicates a CEF-split singlet ground state lying below a doublet at 81(1) K and a quasi-triplet at 152(2) K. The ρ(T) data indicate a metallic behavior, and ρ(H) exhibits a very high positive magnetoresistance, as high as ~300% in 9 T at 2 K. No long range magnetic order or spin-glass behavior was detected in a μSR experiment down to 1.2 K.
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Affiliation(s)
- V K Anand
- ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, UK.
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Pregelj M, Zorko A, Zaharko O, Arčon D, Komelj M, Hillier AD, Berger H. Persistent spin dynamics intrinsic to amplitude-modulated long-range magnetic order. Phys Rev Lett 2012; 109:227202. [PMID: 23368156 DOI: 10.1103/physrevlett.109.227202] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2012] [Indexed: 06/01/2023]
Abstract
An incommensurate elliptical helical magnetic structure in the frustrated coupled-spin-chain system FeTe(2)O(5)Br is surprisingly found to persist down to 53(3) mK (T/T(N)~1/200), according to neutron scattering and muon spin relaxation. In this state, finite spin fluctuations at T→0 are evidenced by muon depolarization, which is in agreement with specific-heat data indicating the presence of both gapless and gapped excitations. We thus show that the amplitude-modulated magnetic order intrinsically accommodates contradictory persistent spin dynamics and long-range order and can serve as a model structure to investigate their coexistence.
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Affiliation(s)
- M Pregelj
- Jožef Stefan Institute, Jamova cesta 39, 1000 Ljubljana, Slovenia
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22
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Hillier AD, Quintanilla J, Mazidian B, Annett JF, Cywinski R. Nonunitary triplet pairing in the centrosymmetric superconductor LaNiGa2. Phys Rev Lett 2012; 109:097001. [PMID: 23002872 DOI: 10.1103/physrevlett.109.097001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2012] [Indexed: 06/01/2023]
Abstract
Muon spin rotation and relaxation experiments on the centrosymmetric intermetallic superconductor LaNiGa2 are reported. The appearance of spontaneous magnetic fields coincides with the onset of superconductivity, implying that the superconducting state breaks time reversal symmetry, similarly to noncentrosymmetric LaNiC2. Only four triplet states are compatible with this observation, all of which are nonunitary triplets. This suggests that LaNiGa2 is the centrosymmetric analogue of LaNiC2. We argue that these materials are representatives of a new family of paramagnetic nonunitary superconductors.
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Affiliation(s)
- A D Hillier
- ISIS Facility, STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Oxfordshire, United Kingdom
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Fåk B, Kermarrec E, Messio L, Bernu B, Lhuillier C, Bert F, Mendels P, Koteswararao B, Bouquet F, Ollivier J, Hillier AD, Amato A, Colman RH, Wills AS. Kapellasite: a kagome quantum spin liquid with competing interactions. Phys Rev Lett 2012; 109:037208. [PMID: 22861895 DOI: 10.1103/physrevlett.109.037208] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2012] [Revised: 05/09/2012] [Indexed: 06/01/2023]
Abstract
Magnetic susceptibility, NMR, muon spin relaxation, and inelastic neutron scattering measurements show that kapellasite, Cu3Zn(OH)6Cl2, a geometrically frustrated spin-1/2 kagome antiferromagnet polymorphic with herbertsmithite, is a gapless spin liquid showing unusual dynamic short-range correlations of noncoplanar cuboc2 type which persist down to 20 mK. The Hamiltonian is determined from a fit of a high-temperature series expansion to bulk susceptibility data and possesses competing exchange interactions. The magnetic specific heat calculated from these exchange couplings is in good agreement with experiment. The temperature dependence of the magnetic structure factor and the muon relaxation rate are calculated in a Schwinger-boson approach and compared to experimental results.
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Affiliation(s)
- B Fåk
- SPSMS, UMR-E CEA/UJF-Grenoble-1, INAC, F-38054 Grenoble Cedex 9, France
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Adroja DT, del Moral A, de la Fuente C, Fraile A, Goremychkin EA, Taylor JW, Hillier AD, Fernandez-Alonso F. Vibron quasibound state in the noncentrosymmetric tetragonal heavy-fermion compound CeCuAl3. Phys Rev Lett 2012; 108:216402. [PMID: 23003286 DOI: 10.1103/physrevlett.108.216402] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2012] [Indexed: 06/01/2023]
Abstract
We have investigated the noncentrosymmetric tetragonal heavy-fermion antiferromagnetic compound CeCuAl3 (T(N)=2.5 K) using inelastic neutron scattering (INS). Our INS results unequivocally reveal the presence of three magnetic excitations centered at 1.3, 9.8, and 20.5 meV. These spectral features cannot be explained within the framework of crystal-electric-field models and recourse to Kramers' theorem for a 4f(1) Ce(3+) ion. To overcome these interpretational difficulties, we have generalized the vibron model of Thalmeier and Fulde for cubic CeAl(2) to tetragonal point-group symmetry with the theoretically calculated vibron form-factor. This extension provides a satisfactory explanation for the position and intensity of the three observed magnetic excitations in CeCuAl3, as well as their dependence on momentum transfer and temperature. On the basis of our analysis, we attribute the observed series of magnetic excitations to the existence of a vibron quasibound state.
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Affiliation(s)
- D T Adroja
- ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, United Kingdom.
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McLaughlin AC, Attfield JP, Van Duijn J, Hillier AD. A μSR study of the magnetoresistive ruthenocuprates RuSr2Nd(1.8-x)Y0.2Ce(x)Cu2O(10-δ) (x = 0.95 and 0.80). J Phys Condens Matter 2011; 23:365704. [PMID: 21865639 DOI: 10.1088/0953-8984/23/36/365704] [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
Zero field muon spin relaxation (ZF-μSR) has been used to study the magnetic properties of the underdoped giant magnetoresistive ruthenocuprates RuSr(2)Nd(1.8-x)Y (0.2)Ce(x)Cu(2)O(10-δ) (x = 0.95, 0.80). The magnetoresistance (MR) is defined so that MR = ((ρ(H)-ρ(0))/ρ(0)) and the giant magnetoresistive ruthenocuprates RuSr(2)Nd(1.8-x)Y(0.2)Ce(x)Cu(2)O(10-δ) exhibit a large reduction in electronic resistivity upon application of a magnetic field. The ZF-μSR results show a gradual loss of initial asymmetry A(0) at the ruthenium spin transition temperature, T(Ru). At the same time the electronic relaxation rate, λ, shows a gradual increase with decreasing temperature below T(Ru). These results have been interpreted as evidence for Cu spin cluster formation below T(Ru). These magnetically ordered clusters grow as the temperature is decreased thus causing the initial asymmetry to decrease slowly. Giant magnetoresistance is observed over a wide temperature range in the materials studied and the magnitude increases as the temperature is reduced from T(Ru) to 4 K which suggests a relation between Cu spin cluster size and |-MR|.
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Affiliation(s)
- A C McLaughlin
- Department of Chemistry, University of Aberdeen, Meston Walk, Aberdeen, UK.
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Anand VK, Adroja DT, Hillier AD, Kockelmann W, Fraile A, Strydom AM. Complex magnetic behavior in the novel Kondo lattice compound CeRhSn₃. J Phys Condens Matter 2011; 23:276001. [PMID: 21673393 DOI: 10.1088/0953-8984/23/27/276001] [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: 05/30/2023]
Abstract
We report the magnetic and transport properties of a new ternary intermetallic compound, CeRhSn₃, using magnetic susceptibility, magnetization, specific heat, electrical resistivity, muon-spin relaxation (μSR) and neutron diffraction investigations. The dc magnetic susceptibility data reveal two magnetic phase transitions at 0.9 and 4 K. The overall behavior of dc susceptibility and magnetization indicates a ferrimagnetic-type phase transition near 4 K. The specific heat data also exhibit sharp λ-type anomalies at 1 and 4 K. The behavior of the specific heat anomaly under the application of a magnetic field suggests that the 1 K transition is probably related to a transition from a ferri- to a ferromagnetic state. The low temperature specific heat exhibits an enhanced Sommerfeld coefficient γ (~100 mJ mol⁻¹ K⁻²) due to the formation of a moderate heavy fermion state. The resistivity of CeRhSn₃ demonstrates an interplay between the RKKY and Kondo interactions which is further modified by the presence of the crystal electric field. Interestingly, the resistivity of the nonmagnetic reference compound, LaRhSn₃, is found to increase with decreasing temperature. Further, the onset of long-range magnetic order below 1 K is confirmed from our μSR study on CeRhSn₃. However, the 4 K transition is not detected in the μSR and low temperature neutron diffraction data. Analysis of the dc magnetic susceptibility data within the framework of a two-sublattice model of ferrimagnetism supports the ferrimagnetic-type transition at 4 K in CeRhSn₃. We have observed an unusual frequency dependence of the peak near 4 K in the ac susceptibility, which shows that the transition temperature shifts toward the lower temperature side with increasing frequency.
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Affiliation(s)
- V K Anand
- ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX, UK.
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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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Miliyanchuk K, Kneidinger F, Blaas-Schenner C, Reith D, Podloucky R, Rogl P, Khan T, Salamakha L, Hilscher G, Michor H, Bauer E, Hillier AD. Platinum metal silicides and germanides: superconductivity in non-centrosymmetric intermetallics. ACTA ACUST UNITED AC 2011. [DOI: 10.1088/1742-6596/273/1/012078] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Tran VH, Hillier AD, Adroja DT, Kaczorowski D. Muon spin rotation and relaxation studies of the filled skutterudite superconductor ThPt4Ge12. J Phys Condens Matter 2010; 22:505701. [PMID: 21406804 DOI: 10.1088/0953-8984/22/50/505701] [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
Longitudinal and transverse field muon spin rotation/relaxation measurements have been carried out on a polycrystalline sample of ThPt(4)Ge(12). The zero-field measurements in the longitudinal geometry do not reveal any signature of a spontaneous internal magnetic field below the superconducting transition temperature, indicating the preservation of time-reversal symmetry in the superconducting state of ThPt(4)Ge(12). From the transverse field data, the zero field magnetic penetration depth, λ(0), was estimated to be 110(15) nm, and then we have estimated the effective mass of the quasiparticles, m*≈4.5m(e), and the superfluid carrier density, n(s)≈1.06 × 10(28) carriers m(-3). We found a marked difference between the zero-field cooling and field-cooled vortex state muon spin relaxation rates, σ(s)(T), below the irreversibility temperature, T(ir) ∼ 2.5 K. A linear field dependence of σ(s)(H) and power law behaviour of σ(s)(T) exhibit a significant deviation from those expected for isotropic BCS-superconductors. The analysis of correlation between the superconducting transition temperature and the effective Fermi temperature within the Uemura classification scheme reveals that the condensation energy in ThPt(4)Ge(12) is comparable to those of exotic superconductors.
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Affiliation(s)
- V H Tran
- Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Wrocław, Poland
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MacLaughlin DE, Hillier AD, Mackie JM, Shu L, Aoki Y, Kikuchi D, Sato H, Tunashima Y, Sugawara H. Comment on "Pronounced enhancement of the lower critical field and critical current deep in the superconducting state of PrOs4Sb12". Phys Rev Lett 2010; 105:019701-019702. [PMID: 20867492 DOI: 10.1103/physrevlett.105.019701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2009] [Indexed: 05/29/2023]
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Tran VH, Hillier AD, Adroja DT, Bukowski Z, Miiller W. Evidence for a spin pseudogap in the normal state of superconducting Mo(3)Sb(7). J Phys Condens Matter 2009; 21:485701. [PMID: 21832528 DOI: 10.1088/0953-8984/21/48/485701] [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
Using muon spin relaxation (μSR) and inelastic neutron scattering (INS) we have investigated the normal state of the superconductor Mo(3)Sb(7) and the reference compound Ru(3)Sn(7). The μSR experiments on Ru(3)Sn(7) reveal static and relatively slow dynamic relaxations, which are ascribed to a random static nuclear dipole field and thermally activated muon motion, respectively. INS experiments on Ru(3)Sn(7), on the other hand, reveal three phononic excitations at 11, 18 and 23 meV, substantiating the assertion of Einstein and Debye oscillations derived from the specific heat and electrical resistivity data. The distinct difference in the μSR as well as INS spectra between Ru(3)Sn(7) and Mo(3)Sb(7) provides strong evidence for a magnetic/electronic nature of the phase transition at T(*) = 50 K in the Mo-based compound. On the basis of the μSR and INS data, the energy spin pseudogap of 150(10) K was estimated. The observed weak magnetism in the dynamic susceptibility χ('')(Q,ω) and residual longitudinal field relaxation at 5 K imply a static ordering or quantum fluctuations.
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Affiliation(s)
- V H Tran
- Institute of Low Temperature and Structure Research, Polish Academy of Sciences, PO Box 1410, 50-950 Wrocław, Poland
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Hillier AD, Quintanilla J, Cywinski R. Evidence for time-reversal symmetry breaking in the noncentrosymmetric superconductor LaNiC2. Phys Rev Lett 2009; 102:117007. [PMID: 19392234 DOI: 10.1103/physrevlett.102.117007] [Citation(s) in RCA: 15] [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: 10/21/2008] [Indexed: 05/27/2023]
Abstract
Muon spin relaxation experiments on the noncentrosymmetric intermetallic superconductor LaNiC2 are reported. We find that the onset of superconductivity coincides with the appearance of spontaneous magnetic fields, implying that in the superconducting state time-reversal symmetry is broken. An analysis of the possible pairing symmetries suggests only four triplet states compatible with this observation, all of them nonunitary. They include the intriguing possibility of triplet pairing with the full point group symmetry of the crystal, which is possible only in a noncentrosymmetric superconductor.
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Affiliation(s)
- A D Hillier
- ISIS facility, STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Oxfordshire, OX11 0QX, United Kingdom
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Bert F, Mendels P, Olariu A, Blanchard N, Collin G, Amato A, Baines C, Hillier AD. Direct evidence for a dynamical ground state in the highly frustrated Tb(2)Sn(2)O(7) pyrochlore. Phys Rev Lett 2006; 97:117203. [PMID: 17025926 DOI: 10.1103/physrevlett.97.117203] [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: 03/07/2006] [Indexed: 05/12/2023]
Abstract
mSR experiments have been performed on a powder sample of the "ordered spin ice" Tb(2)Sn(2)O(7) pyrochlore. At base temperature (T=35 mK), the muon relaxation is found to be of dynamical nature, which demonstrates that strong fluctuations persist below the ferromagnetic transition (T(C)=0.87 K). Hints of long-range ordering appear as oscillations of the muon polarization when an external field is applied and also as a hysteretic behavior below T(C). We propose that dynamics results from fluctuations of clusters of correlated spins with the ordered spin ice structure.
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Affiliation(s)
- F Bert
- Laboratoire de Physique des Solides, UMR 8502, Université Paris-Sud, 91405 Orsay, France
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Mendels P, Bono D, Bobroff J, Collin G, Colson D, Blanchard N, Alloul H, Mukhamedshin I, Bert F, Amato A, Hillier AD. Cascade of bulk magnetic phase transitions in NaxCoO2 as studied by muon spin rotation. Phys Rev Lett 2005; 94:136403. [PMID: 15904009 DOI: 10.1103/physrevlett.94.136403] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2004] [Revised: 12/29/2004] [Indexed: 05/02/2023]
Abstract
Using muon spin rotation, well-defined bulk approximately 100% magnetic phases in NaxCoO2 are revealed. A novel magnetic phase is detected for x=0.85 with the highest transition temperature ever observed for x>or=0.75. This stresses the diversity of x>or=0.75 magnetic phases and the link between magnetic and structural degrees of freedom. For the charge-ordered x=0.50 compound, a cascade of transitions is observed below 85 K. From a detailed analysis of our data, we conclude that the ordered moment varies continuously with temperature and suggest that the two secondary transitions at 48 and 29 K correspond to a moderate reorientation of antiferromagnetically coupled moments.
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Affiliation(s)
- P Mendels
- Laboratoire de Physique des Solides, UMR 8502, Université Paris-Sud, 91405 Orsay, France
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Sanna S, Allodi G, Concas G, Hillier AD, De Renzi R. Nanoscopic coexistence of magnetism and superconductivity in YBa2Cu3O6+x detected by muon spin rotation. Phys Rev Lett 2004; 93:207001. [PMID: 15600957 DOI: 10.1103/physrevlett.93.207001] [Citation(s) in RCA: 4] [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: 03/25/2004] [Indexed: 05/24/2023]
Abstract
We performed zero and transverse field muon spin rotation experiments on a large number of YBa2Cu3O6+x samples. We detect the coexistence of antiferromagnetic (AF) short range magnetism with superconductivity below T(f) < or = 10 K in compositions 0.37 < or = x < or = 0.39. Most muons experience local AF fields, even when a SQUID detects a full superconducting volume fraction, which points to a local minimal interference organization of short AF stripes embedded in the superconductor. A detailed phase diagram is produced and the consequences of the minimal interference are discussed.
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Affiliation(s)
- S Sanna
- Dipartimento di Fisica e Unità INFM di Cagliari, I 09042 Monserrato (Ca), Italy
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Bono D, Mendels P, Collin G, Blanchard N, Bert F, Amato A, Baines C, Hillier AD. muSR study of the quantum dynamics in the frustrated S=3/2 kagomé bilayers. Phys Rev Lett 2004; 93:187201. [PMID: 15525201 DOI: 10.1103/physrevlett.93.187201] [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: 05/21/2004] [Indexed: 05/24/2023]
Abstract
We present muSR experiments in the S=3/2 kagomé bilayer compound Ba(2)Sn(2)ZnGa(10-7p)Cr(7p)O22 [BSZCGO(p)] and compare it to the isostructural SrCr(9p)Ga(12-9p)O19 [SCGO(p)], including for the latter new results for p > or =0.89. Quantum-dynamical low energy magnetic excitations are evidenced in this novel compound. We study the evolution of the muon relaxation rate with p, T, and field. A phenomenological model for the muon relaxation based on sporadic dynamics due to spin excitations in a singlet sea proposed by Uemura et al. is extended to all fields and T range. Its connection to the RVB picture is discussed, and we argue that such coherent states might mediate the interactions between "impurities" which induce the spin glass freezing.
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Affiliation(s)
- D Bono
- Laboratoire de Physique des Solides, UMR 8502, Université Paris-Sud, 91405 Orsay, France
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