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Giles-Donovan N, Hillier AD, Ishida K, Hampshire BV, Giblin SR, Roessli B, Gehring PM, Xu G, Li X, Luo H, Cochran S, Stock C. Magnetic skin effect in Pb(Fe _{1/2}$Nb _{1/2}$)O 3. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2024; 36:435802. [PMID: 39025119 DOI: 10.1088/1361-648x/ad6523] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2024] [Accepted: 07/18/2024] [Indexed: 07/20/2024]
Abstract
Relaxor-ferroelectrics display exceptional dielectric properties resulting from the underlying random dipolar fields induced by strong chemical inhomogeneity. An unusual structural aspect of relaxors is a skin-effect where the near-surface region in single crystals exhibit structures and critical phenomena that differ from the bulk. Relaxors are unique in that this skin effect extends over a macroscopic lengthscale of ∼100 μmwhereas usual surface layers only extend over a few unit cells (or ∼nm). We present a muon spectroscopy study of Pb(Fe_{1/2}Nb_{1/2})O3(PFN) which displays ferroelectric order, including many relaxor-like dielectric properties such as a frequency broadened dielectric response, and antiferromagnetism with spatially short-range polar correlations and hence can be termed a multiferroic. In terms of the magnetic behavior determined by the Fe3+(S=5/2,L ≈ 0) ions, PFN has been characterized as a unique example of a 'cluster spin-glass'. We use variable momentum muon spectroscopy to study the depth dependence of the slow magnetic relaxations in a large 1 cm3crystal of PFN. Zero-fieldpositivemuon spin relaxation is parameterized using a stretched exponential, indicative of a distribution of relaxation rates of the Fe3+spins. This bandwidth of frequencies changes as a function of muon momentum, indicative of a change in the Fe3+relaxation rates as a function of muon implantation depth in our single crystal. Usingnegativemuon elemental analysis, we find small-to-no measurable change in the Fe3+/Nb5+concentration with depth implying that chemical concentration alone cannot account for the change in the relaxational dynamics. PFN displays an analogous magnetic skin effect reported to exist in the structural properties of relaxor-ferroelectrics.
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Affiliation(s)
- N Giles-Donovan
- Centre for Medical and Industrial Ultrasonics, James Watt School of Engineering, University of Glasgow, Glasgow G12 8QQ, United Kingdom
| | - A D Hillier
- ISIS Facility, Rutherford Appleton Laboratory, Harwell, Didcot, United Kingdom
| | - K Ishida
- ISIS Facility, Rutherford Appleton Laboratory, Harwell, Didcot, United Kingdom
- RIKEN Nishina Center, RIKEN, Wako, Saitama, Japan
| | - B V Hampshire
- ISIS Facility, Rutherford Appleton Laboratory, Harwell, Didcot, United Kingdom
- Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - S R Giblin
- School of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA, United Kingdom
| | - B Roessli
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut (PSI), 5232 Villigen PSI, Switzerland
| | - P M Gehring
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899-6100, United States of America
| | - G Xu
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899-6100, United States of America
| | - X Li
- Chinese Academy of Sciences, Shanghai Institute of Ceramics, Shanghai, People's Republic of China
| | - H Luo
- Chinese Academy of Sciences, Shanghai Institute of Ceramics, Shanghai, People's Republic of China
| | - S Cochran
- Centre for Medical and Industrial Ultrasonics, James Watt School of Engineering, University of Glasgow, Glasgow G12 8QQ, United Kingdom
| | - C Stock
- School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom
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Hiraka H, Lee J, Jeon B, Seong BS, Cho S. Commissioning of neutron triple-axis spectrometers at HANARO. NUCLEAR ENGINEERING AND TECHNOLOGY 2020. [DOI: 10.1016/j.net.2020.03.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Stock C, Songvilay M, Gehring PM, Xu G, Roessli B. Broadband critical dynamics in disordered lead-based perovskites. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:374012. [PMID: 32252031 DOI: 10.1088/1361-648x/ab86ee] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Accepted: 04/06/2020] [Indexed: 06/11/2023]
Abstract
Materials based on the cubic perovskite unit cell continue to provide the basis for technologically important materials with two notable recent examples being lead-based relaxor piezoelectrics and lead-based organic-inorganic halide photovoltaics. These materials carry considerable disorder, arising from site substitution in relaxors and molecular vibrations in the organic-inorganics, yet much of our understanding of these systems derives from the initial classic work of Prof. Roger A Cowley, who applied both theory and neutron scattering methods while at Chalk River Laboratories to the study of lattice vibrations in SrTiO3. Neutron scattering continues to play a vital role in characterizing lattice vibrations in perovskites owing to the simple cross section and the wide range of energy resolutions achievable with current neutron instrumentation. We discuss the dynamics that drive the phase transitions in the relaxors and organic-inorganic lead-halides in terms of neutron scattering and compare them to those in phase transitions associated with a 'central peak' and also a soft mode. We review some of the past experimental work on these materials and present new data from high-resolution time-of-flight backscattering spectroscopy taken on organic-inorganic perovskites. We will show that the structural transitions in disordered lead-based perovskites are driven by a broad frequency band of excitations.
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Affiliation(s)
- C Stock
- School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3FD, United Kingdom
| | - M Songvilay
- School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3FD, United Kingdom
| | - P M Gehring
- NIST Center for Neutron Research, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland, 20899, United States of America
| | - Guangyong Xu
- NIST Center for Neutron Research, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland, 20899, United States of America
| | - B Roessli
- Laboratory for Neutron Scattering and Imaging (LNS), Paul Scherrer Institute (PSI), 5232 Villigen PSI, Switzerland
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Matsuura M, Sasaki T, Iguchi S, Gati E, Müller J, Stockert O, Piovano A, Böhm M, Park JT, Biswas S, Winter SM, Valentí R, Nakao A, Lang M. Lattice Dynamics Coupled to Charge and Spin Degrees of Freedom in the Molecular Dimer-Mott Insulator κ-(BEDT-TTF)_{2}Cu[N(CN)_{2}]Cl. PHYSICAL REVIEW LETTERS 2019; 123:027601. [PMID: 31386497 DOI: 10.1103/physrevlett.123.027601] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2018] [Revised: 05/24/2019] [Indexed: 06/10/2023]
Abstract
Inelastic neutron scattering measurements on the molecular dimer-Mott insulator κ-(BEDT-TTF)_{2}Cu[N(CN)_{2}]Cl reveal a phonon anomaly in a wide temperature range. Starting from T_{ins}∼50-60 K where the charge gap opens, the low-lying optical phonon modes become overdamped upon cooling towards the antiferromagnetic ordering temperature T_{N}=27 K, where also a ferroelectric ordering at T_{FE}≈T_{N} occurs. Conversely, the phonon damping becomes small again when spins and charges are ordered below T_{N}, while no change of the lattice symmetry is observed across T_{N} in neutron diffraction measurements. We assign the phonon anomalies to structural fluctuations coupled to charge and spin degrees of freedom in the BEDT-TTF molecules.
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Affiliation(s)
- Masato Matsuura
- Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society (CROSS), Tokai, Ibaraki 319-1106, Japan
| | - Takahiko Sasaki
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - Satoshi Iguchi
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - Elena Gati
- Institute of Physics, Goethe-University Frankfurt, 60438 Frankfurt (M), Germany
| | - Jens Müller
- Institute of Physics, Goethe-University Frankfurt, 60438 Frankfurt (M), Germany
| | - Oliver Stockert
- Max-Planck-Institut für Chemische Physik fester Stoffe, D-01187 Dresden, Germany
| | - Andrea Piovano
- Institut Laue-Langevin, 71 avenue des Martyrs, 38042 Grenoble Cedex 9, France
| | - Martin Böhm
- Institut Laue-Langevin, 71 avenue des Martyrs, 38042 Grenoble Cedex 9, France
| | - Jitae T Park
- Heinz Maier-Leibnitz Zentrum (MLZ), Technische Universität München, Lichtenbergstr. 1, 85748 Garching, Germany
| | - Sananda Biswas
- Institute for Theoretical Physics, Goethe-University Frankfurt, 60438 Frankfurt (M), Germany
| | - Stephen M Winter
- Institute for Theoretical Physics, Goethe-University Frankfurt, 60438 Frankfurt (M), Germany
| | - Roser Valentí
- Institute for Theoretical Physics, Goethe-University Frankfurt, 60438 Frankfurt (M), Germany
| | - Akiko Nakao
- Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society (CROSS), Tokai, Ibaraki 319-1106, Japan
| | - Michael Lang
- Institute of Physics, Goethe-University Frankfurt, 60438 Frankfurt (M), Germany
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Takenaka H, Grinberg I, Liu S, Rappe AM. Slush-like polar structures in single-crystal relaxors. Nature 2017; 546:391-395. [DOI: 10.1038/nature22068] [Citation(s) in RCA: 148] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2016] [Accepted: 03/09/2017] [Indexed: 12/27/2022]
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Overy AR, Cairns AB, Cliffe MJ, Simonov A, Tucker MG, Goodwin AL. Design of crystal-like aperiodic solids with selective disorder-phonon coupling. Nat Commun 2016; 7:10445. [PMID: 26842772 PMCID: PMC4742854 DOI: 10.1038/ncomms10445] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Accepted: 12/11/2015] [Indexed: 11/09/2022] Open
Abstract
Functional materials design normally focuses on structurally ordered systems because disorder is considered detrimental to many functional properties. Here we challenge this paradigm by showing that particular types of strongly correlated disorder can give rise to useful characteristics that are inaccessible to ordered states. A judicious combination of low-symmetry building unit and high-symmetry topological template leads to aperiodic ‘procrystalline' solids that harbour this type of disorder. We identify key classes of procrystalline states together with their characteristic diffraction behaviour, and establish mappings onto known and target materials. The strongly correlated disorder found in these systems is associated with specific sets of modulation periodicities distributed throughout the Brillouin zone. Lattice dynamical calculations reveal selective disorder-driven phonon broadening that resembles the poorly understood ‘waterfall' effect observed in relaxor ferroelectrics. This property of procrystalline solids suggests a mechanism by which strongly correlated topological disorder might allow independently optimized thermal and electronic transport behaviour, such as required for high-performance thermoelectrics. Conventional crystallography focuses on structurally-ordered systems, where interesting physics or novel material functions emerge. Here, Overy et al. propose an approach of designing functional materials with strongly correlated disorder, which can couple with phonons to affect lattice dynamics.
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Affiliation(s)
- Alistair R Overy
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford OX1 3QR, UK.,Diamond Light Source, Chilton, Oxfordshire, OX11 0DE, UK
| | - Andrew B Cairns
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford OX1 3QR, UK.,European Synchrotron Radiation Facility, 71 avenue des Martyrs, 38043 Grenoble, France
| | - Matthew J Cliffe
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford OX1 3QR, UK.,Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK
| | - Arkadiy Simonov
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford OX1 3QR, UK
| | - Matthew G Tucker
- Diamond Light Source, Chilton, Oxfordshire, OX11 0DE, UK.,ISIS Facility, Rutherford Appleton Laboratory, Harwell Oxford, Didcot, Oxfordshire OX11 0QX, UK
| | - Andrew L Goodwin
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford OX1 3QR, UK
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8
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Phonon localization drives polar nanoregions in a relaxor ferroelectric. Nat Commun 2014; 5:3683. [PMID: 24718289 DOI: 10.1038/ncomms4683] [Citation(s) in RCA: 86] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2013] [Accepted: 03/18/2014] [Indexed: 11/08/2022] Open
Abstract
Relaxor ferroelectrics exemplify a class of functional materials where interplay between disorder and phase instability results in inhomogeneous nanoregions. Although known for about 30 years, there is no definitive explanation for polar nanoregions (PNRs). Here we show that ferroelectric phonon localization drives PNRs in relaxor ferroelectric PMN-30%PT using neutron scattering. At the frequency of a preexisting resonance mode, nanoregions of standing ferroelectric phonons develop with a coherence length equal to one wavelength and the PNR size. Anderson localization of ferroelectric phonons by resonance modes explains our observations and, with nonlinear slowing, the PNRs and relaxor properties. Phonon localization at additional resonances near the zone edges explains competing antiferroelectric distortions known to occur at the zone edges. Our results indicate the size and shape of PNRs that are not dictated by complex structural details, as commonly assumed, but by phonon resonance wave vectors. This discovery could guide the design of next generation relaxor ferroelectrics.
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Abstract
PbZr(1-x)Ti(x)O3 (PZT) and Pb(Mg1/3Nb2/3)(1-x)Ti(x)O3 (PMN-xPT) are complex lead-oxide perovskites that display exceptional piezoelectric properties for pseudorhombohedral compositions near a tetragonal phase boundary. In PZT these compositions are ferroelectrics, but in PMN-xPT they are relaxors because the dielectric permittivity is frequency dependent and exhibits non-Arrhenius behavior. We show that the nanoscale structure unique to PMN-xPT and other lead-oxide perovskite relaxors is absent in PZT and correlates with a greater than 100% enhancement of the longitudinal piezoelectric coefficient in PMN-xPT relative to that in PZT. By comparing dielectric, structural, lattice dynamical, and piezoelectric measurements on PZT and PMN-xPT, two nearly identical compounds that represent weak and strong random electric field limits, we show that quenched (static) random fields establish the relaxor phase and identify the order parameter.
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Glinchuk M. Relaxor ferroelectrics: from Cross superparaelectric model to random field theory. ACTA ACUST UNITED AC 2013. [DOI: 10.1179/096797804225012792] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
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11
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Takenaka H, Grinberg I, Rappe AM. Anisotropic local correlations and dynamics in a relaxor ferroelectric. PHYSICAL REVIEW LETTERS 2013; 110:147602. [PMID: 25167037 DOI: 10.1103/physrevlett.110.147602] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2012] [Revised: 02/28/2013] [Indexed: 06/03/2023]
Abstract
Relaxor ferroelectrics have been a focus of intense attention due to their anomalous properties, and understanding the structure and dynamics of relaxors has been one of the long-standing challenges in solid-state physics. We investigate the local structure and dynamics in 75%PbMg(1/3)Nb(2/3)O(3)-25%PbTiO(3) using molecular dynamics simulations and the dynamic pair distribution function technique. We show that relaxor transitions can be described by local order parameters. The relaxor phase is characterized by the presence of highly anisotropic correlations between the local cation displacements that resemble the hydrogen bond network in water. This contradicts the current model of polar nanoregion inside a nonpolar matrix. We therefore suggest a new model of a homogeneous random network of anisotropically coupled dipoles.
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Affiliation(s)
- Hiroyuki Takenaka
- The Makineni Theoretical Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, USA
| | - Ilya Grinberg
- The Makineni Theoretical Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, USA
| | - Andrew M Rappe
- The Makineni Theoretical Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, USA
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12
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Xu G. Probing local polar structures in PZN-xPT and PMN-xPT relaxor ferroelectrics with neutron and x-ray scattering. ACTA ACUST UNITED AC 2011. [DOI: 10.1088/1742-6596/320/1/012081] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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13
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Delaire O, Ma J, Marty K, May AF, McGuire MA, Du MH, Singh DJ, Podlesnyak A, Ehlers G, Lumsden MD, Sales BC. Giant anharmonic phonon scattering in PbTe. NATURE MATERIALS 2011; 10:614-9. [PMID: 21642983 DOI: 10.1038/nmat3035] [Citation(s) in RCA: 186] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2011] [Accepted: 04/22/2011] [Indexed: 05/24/2023]
Abstract
Understanding the microscopic processes affecting the bulk thermal conductivity is crucial to develop more efficient thermoelectric materials. PbTe is currently one of the leading thermoelectric materials, largely thanks to its low thermal conductivity. However, the origin of this low thermal conductivity in a simple rocksalt structure has so far been elusive. Using a combination of inelastic neutron scattering measurements and first-principles computations of the phonons, we identify a strong anharmonic coupling between the ferroelectric transverse optic mode and the longitudinal acoustic modes in PbTe. This interaction extends over a large portion of reciprocal space, and directly affects the heat-carrying longitudinal acoustic phonons. The longitudinal acoustic-transverse optic anharmonic coupling is likely to play a central role in explaining the low thermal conductivity of PbTe. The present results provide a microscopic picture of why many good thermoelectric materials are found near a lattice instability of the ferroelectric type.
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Affiliation(s)
- O Delaire
- Neutron Scattering Science Division, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, Tennessee 37831, USA.
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Grinberg I, Shin YH, Rappe AM. Molecular dynamics study of dielectric response in a relaxor ferroelectric. PHYSICAL REVIEW LETTERS 2009; 103:197601. [PMID: 20365954 DOI: 10.1103/physrevlett.103.197601] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2009] [Indexed: 05/29/2023]
Abstract
We use atomistic molecular dynamics simulations to study relaxor behavior in the 0.75 PbMg(1/3)Nb(2/3)O(3)-0.25 PbTiO(3) material. Even for a fairly small simulation size of 1000 atoms, the system exhibits frequency dispersion and deviation from the Curie-Weiss law typical of relaxor materials. Analysis of the time autocorrelation functions for individual atoms allows us to identify the Nb atoms with a high concentration of neighboring Ti atoms as the nucleation sites for the relaxor behavior. This is due to the higher coupling between the cation displacements induced by the presence of overbonded oxygen atoms.
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Affiliation(s)
- Ilya Grinberg
- The Makineni Theoretical Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, USA
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15
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Xu G, Wen J, Stock C, Gehring PM. Phase instability induced by polar nanoregions in a relaxor ferroelectric system. NATURE MATERIALS 2008; 7:562-566. [PMID: 18469821 DOI: 10.1038/nmat2196] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2007] [Accepted: 04/16/2008] [Indexed: 05/26/2023]
Abstract
Relaxor ferroelectrics are a special class of material that exhibit an enormous electromechanical response and are easily polarized with an external field. These properties make them attractive for applications as sensors and actuators. Local clusters of randomly oriented polarization, known as polar nanoregions (PNRs), are specific to relaxor ferroelectrics and play a key role in governing their dielectric properties. Here, we show through neutron inelastic scattering experiments that the PNRs can also significantly affect the structural properties of the relaxor ferroelectric Pb(Zn(1/3)Nb(2/3))O(3)-4.5%PbTiO(3) (PZN-4.5%PT). A strong interaction is found between the PNRs and the propagation of acoustic phonons. A comparison between acoustic phonons propagating along different directions reveals a large asymmetry in the lattice dynamics that is induced by the PNRs. We suggest that a phase instability induced by this PNR-phonon interaction may contribute to the ultrahigh piezoelectric response of this and related relaxor ferroelectric materials. Our results naturally explain the emergence of the various observed monoclinic phases in these systems.
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Affiliation(s)
- Guangyong Xu
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA.
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16
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Grinberg I, Juhás P, Davies PK, Rappe AM. Relationship between local structure and relaxor behavior in perovskite oxides. PHYSICAL REVIEW LETTERS 2007; 99:267603. [PMID: 18233605 DOI: 10.1103/physrevlett.99.267603] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2006] [Revised: 06/03/2007] [Indexed: 05/25/2023]
Abstract
Despite intensive investigations over the past five decades, the microscopic origins of the fascinating dielectric properties of ABO3 relaxor ferroelectrics are currently poorly understood. Here, we show that the frequency dispersion that is the hallmark of relaxor behavior is quantitatively related to the crystal chemical characteristics of the solid solution. Density functional theory is used in conjunction with experimental determination of cation arrangement to identify the 0 K structural motifs. These are then used to parametrize a simple phenomenological Landau theory that predicts the universal dependence of frequency dispersion on the solid solution cation arrangement and off-center cation displacements.
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Affiliation(s)
- Ilya Grinberg
- The Makineni Theoretical Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, USA
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Roth M, Mojaev E, Dul'kin E, Gemeiner P, Dkhil B. Phase transition at a nanometer scale detected by acoustic emission within the cubic phase Pb(Zn1/3Nb2/3)O3-xPbTiO3 relaxor ferroelectrics. PHYSICAL REVIEW LETTERS 2007; 98:265701. [PMID: 17678104 DOI: 10.1103/physrevlett.98.265701] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2007] [Indexed: 05/16/2023]
Abstract
Pb(Zn(1/3)Nb(2/3))O3-xPbTiO(3) (x=4.5%-12%) relaxor ferroelectric crystals have been studied by means of acoustic emission (AE) in the 400-540 K temperature range. An anomalous AE activity independent of the ground state relaxor/morphotropic/ferroelectric crossover has been revealed at around 500 K, and it is associated with the "waterfall" feature related to the existence of polar nanoregions (PNRs). The 500 K AE anomaly is attributed to local martensitelike cubic-to-tetragonal ferroelectric transitions within the PNRs imbedded in a nonpolar (cubic) matrix.
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Affiliation(s)
- Michael Roth
- Faculty of Science, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
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Kamba S, Kempa M, Bovtun V, Petzelt J, Brinkman K, Setter N. Soft and central mode behaviour in PbMg(1/3)Nb(2/3)O(3) relaxor ferroelectric. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2005; 17:3965-3974. [PMID: 21690711 DOI: 10.1088/0953-8984/17/25/022] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The relaxor ferroelectric PbMg(1/3)Nb(2/3)O(3) (PMN) is investigated by means of dielectric and Fourier transform far infrared transmission spectroscopy in the frequency range from 10 kHz to 15 THz at temperatures between 20 and 900 K using mostly thin films on infrared transparent sapphire substrates. While the thin film relaxors display reduced dielectric permittivity at low frequencies, their high frequency lattice response is shown to be the same as for single-crystal/ceramic specimens. In contrast to the results of inelastic neutron scattering, the optic soft mode is found to be underdamped at all temperatures. On heating, the TO1 soft phonon follows the Cochran law with an extrapolated critical temperature of 670 K near to the Burns temperature. Above 450 K the soft mode frequency levels off near 50 cm(-1) and above the Burns temperature it slightly hardens. Central-mode-type dispersion assigned to the dynamics of polar nanoclusters appears below the Burns temperature at frequencies near to but below the soft mode and slows down and broadens dramatically on cooling, finally, below the freezing temperature of 200 K, giving rise to frequency independent losses from the microwave range down. A new explanation of the phonon 'waterfall' effect in inelastic neutron scattering spectra is proposed.
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Affiliation(s)
- S Kamba
- Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague 8, Czech Republic
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Hlinka J, Kamba S, Petzelt J, Kulda J, Randall CA, Zhang SJ. Origin of the "waterfall" effect in phonon dispersion of relaxor perovskites. PHYSICAL REVIEW LETTERS 2003; 91:107602. [PMID: 14525505 DOI: 10.1103/physrevlett.91.107602] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2003] [Indexed: 05/24/2023]
Abstract
We have undertaken an inelastic neutron scattering study of the perovskite relaxor ferroelectric Pb(Zn(1/3)Nb(2/3))O3 with 8% PbTiO3 (PZN-8%PT) in order to elucidate the origin of the previously reported unusual kink on the low frequency transverse phonon dispersion curve (known as the "waterfall effect"). We show that its position (q(wf)) depends on the choice of the Brillouin zone and that the relation of q(wf) to the size of the polar nanoregions is highly improbable. The waterfall phenomenon is explained in the framework of a simple model of coupled damped harmonic oscillators representing the acoustic and optic phonon branches.
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Affiliation(s)
- J Hlinka
- Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 18221 Praha 8, Czech Republic
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20
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Zalar B, Laguta VV, Blinc R. NMR evidence for the coexistence of order-disorder and displacive components in barium titanate. PHYSICAL REVIEW LETTERS 2003; 90:037601. [PMID: 12570522 DOI: 10.1103/physrevlett.90.037601] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2002] [Indexed: 05/24/2023]
Abstract
A quadrupole coupling induced 47Ti and 49Ti satellite background which transforms into well-defined satellite lines below T(c) in the ferroelectric phase has been observed in the cubic phase of an ultrapure BaTiO3 single crystal. The results demonstrate the coexistence of a displacive and order-disorder component in the phase transition mechanism and tetragonal breaking of the cubic symmetry due to biased Ti motion between off-center sites in the paraelectric phase above T(c).
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Affiliation(s)
- Bostjan Zalar
- J. Stefan Institute, University of Ljubljana, Jamova 39, 1000 Ljubljana, Slovenia
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Colla EV, Chao LK, Weissman MB. Barkhausen noise in a relaxor ferroelectric. PHYSICAL REVIEW LETTERS 2002; 88:017601. [PMID: 11800985 DOI: 10.1103/physrevlett.88.017601] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2001] [Indexed: 05/23/2023]
Abstract
Barkhausen noise, including both periodic and aperiodic components, is found in and near the relaxor regime of a familiar relaxor ferroelectric, PbMg(1/3)Nb(2/3)O3, driven by a periodic electric field. The temperature dependences of both the amplitude and spectral form show that the size of the coherent changes in the dipole moment shrink as the relaxor regime is entered, contrary to expectations based on some simple models.
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Affiliation(s)
- Eugene V Colla
- Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, IL 61801-3080, USA
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Gehring PM, Wakimoto S, Ye ZG, Shirane G. Soft mode dynamics above and below the Burns temperature in the relaxor Pb(Mg1/3Nb2/3)O3. PHYSICAL REVIEW LETTERS 2001; 87:277601. [PMID: 11800914 DOI: 10.1103/physrevlett.87.277601] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2001] [Indexed: 05/23/2023]
Abstract
We report neutron inelastic scattering measurements of the lowest-energy transverse optic (TO) phonon branch in the relaxor Pb(Mg1/3Nb2/3)O3 from 400 to 1100 K. Far above the Burns temperature T(d) approximately 620 K we observe well-defined propagating TO modes at all wave vectors q, and a zone center TO mode that softens in a manner consistent with that of a ferroelectric soft mode. Below T(d) the zone center TO mode is overdamped. This damping extends up to, but not above, the waterfall wave vector q(wf), which is a measure of the average size of the polar nanoregions.
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Affiliation(s)
- P M Gehring
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
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