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Kashikar R, Valdespino A, Ogg C, Uppgard E, Lisenkov S, Ponomareva I. Ferroelectricity in Ultrathin Halide Perovskites. NANO LETTERS 2024; 24:10624-10630. [PMID: 39140493 DOI: 10.1021/acs.nanolett.4c02940] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/15/2024]
Abstract
Ferroelectricity has recently been demonstrated in germanium-based halide perovskites. We use first-principles-based simulations to study 4-18 nm CsGeBr3 films and develop a theory for ferroelectric ultrathin films. The theory introduces (i) a local order parameter, which identifies phase transitions into both monodomain and polydomain phases, and (ii) a dipole pattern classifier, which allows efficient and reliable identification of dipole patterns. Application of the theory to both halides CsGeBr3 and CsGeI3 and oxide BiFeO3 ultrathin ferroelectrics reveals two distinct scenarios. First, the films transition into a monodomain phase below the critical value of the residual depolarizing field. Above this critical value, the second scenario occurs, and the film undergoes a transition into a nanodomain phase. The two scenarios exhibit opposite responses of Curie temperature to thickness reduction. Application of a dipole pattern classifier reveals rich nanodomain phases in halide films: nanostripes, labyrinths, zig-zags, pillars, and lego domains.
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Affiliation(s)
- Ravi Kashikar
- Department of Physics, University of South Florida, Tampa, Florida 33620, United States
| | - Arlies Valdespino
- Department of Physics, University of South Florida, Tampa, Florida 33620, United States
| | - Charlton Ogg
- Department of Physics, University of South Florida, Tampa, Florida 33620, United States
| | - Edvin Uppgard
- Department of Physics, University of South Florida, Tampa, Florida 33620, United States
| | - S Lisenkov
- Department of Physics, University of South Florida, Tampa, Florida 33620, United States
| | - I Ponomareva
- Department of Physics, University of South Florida, Tampa, Florida 33620, United States
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2
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Zhang F, Zhang J, Fang D, Zhang Y, Wang D. Unusual magnetic interaction in CrTe: insights from machine-learning and empirical models. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2023; 36:135804. [PMID: 38091625 DOI: 10.1088/1361-648x/ad154f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2023] [Accepted: 12/13/2023] [Indexed: 12/28/2023]
Abstract
Chromium telluride (CrTe) has received much attention due to its small magnetic anisotropy, which hosts the potential for complex magnetic structures. However, its magnetic properties have been relatively unexplored with numerical simulations, as the magnetic interactions inside are quite unusual. In this study, we employ both a machine-learning model and an empirical model to investigate the magnetic phase transitions of bulk and monolayer CrTe, revealing the existence of unusual magnetic interaction, which can be captured by the machine-learning model but not the simple empirical model. Furthermore, our results also demonstrate that magnetic moments further apart exhibit stronger interactions than those in closer proximity, deviating from typical behavior.
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Affiliation(s)
- F Zhang
- School of Microelectronics & State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049, People's Republic of China
- Key Lab of Micro-Nano Electronics and System Integration of Xi'an City, Xi'an Jiaotong University, Xi'an 710049, People's Republic of China
| | - J Zhang
- School of Microelectronics & State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049, People's Republic of China
- Key Lab of Micro-Nano Electronics and System Integration of Xi'an City, Xi'an Jiaotong University, Xi'an 710049, People's Republic of China
| | - D Fang
- MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, School of Physics, Xi'an Jiaotong University, Xi'an 710049, People's Republic of China
| | - Y Zhang
- School of Physics, Henan Normal University, Xinxiang 453007, People's Republic of China
| | - D Wang
- School of Microelectronics & State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049, People's Republic of China
- Key Lab of Micro-Nano Electronics and System Integration of Xi'an City, Xi'an Jiaotong University, Xi'an 710049, People's Republic of China
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3
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Bennett D, Muñoz Basagoiti M, Artacho E. Electrostatics and domains in ferroelectric superlattices. ROYAL SOCIETY OPEN SCIENCE 2020; 7:201270. [PMID: 33391805 PMCID: PMC7735331 DOI: 10.1098/rsos.201270] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Accepted: 10/14/2020] [Indexed: 06/10/2023]
Abstract
The electrostatics arising in ferroelectric/dielectric two-dimensional heterostructures and superlattices is revisited within a Kittel model in order to define and complete a clear paradigmatic reference for domain formation. The screening of the depolarizing field in isolated ferroelectric or polar thin films via the formation of 180° domains is well understood, where the width of the domains w grows as the square-root of the film thickness d, following Kittel's Law for thick enough films (w ≪ d). For thinner films, a minimum is reached for w before diverging to a monodomain. Although this behaviour is known to be qualitatively unaltered when the dielectric environment of the film is modified, we consider the quantitative changes in that behaviour induced on the ferroelectric film by different dielectric settings: as deposited on a dielectric substrate, sandwiched between dielectrics, and in a superlattice of alternating ferroelectric/dielectric films. The model assumes infinitely thin domain walls, and therefore is not expected to be reliable for film thickness in the nanometre scale. The polarization field P(r) does vary in space, deviating from ±P S , following the depolarizing field in linear response, but the model does not include a polarization-gradient term as would appear in a Ginzburg-Landau free energy. The model is, however, worth characterizing, both as paradigmatic reference, and as applicable to not-so-thin films. The correct renormalization of parameters is obtained for the thick-film square-root behaviour in the mentioned settings, and the sub-Kittel regime is fully characterized. New results are presented alongside well-known ones for a comprehensive description. Among the former, a natural separation between strong and weak ferroelectric coupling in superlattices is found, which depends exclusively on the dielectric anisotropy of the ferroelectric layer.
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Affiliation(s)
- Daniel Bennett
- Theory of Condensed Matter, Cavendish Laboratory, Department of Physics, J J Thomson Avenue, Cambridge CB3 0HE, UK
| | - Maitane Muñoz Basagoiti
- Faculty of Science and Technology, University of the Basque Country, Barrio Sarriena 48940 Leioa, Spain
- Gulliver Lab UMR 7083, ESPCI PSL Research University, 75005 Paris, France
- CIC Nanogune and DIPC, Tolosa Hiribidea 76, 20018 San Sebastian, Spain
| | - Emilio Artacho
- Theory of Condensed Matter, Cavendish Laboratory, Department of Physics, J J Thomson Avenue, Cambridge CB3 0HE, UK
- CIC Nanogune and DIPC, Tolosa Hiribidea 76, 20018 San Sebastian, Spain
- Ikerbasque, Basque Foundation for Science, 48011 Bilbao, Spain
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Burns SR, Paull O, Juraszek J, Nagarajan V, Sando D. The Experimentalist's Guide to the Cycloid, or Noncollinear Antiferromagnetism in Epitaxial BiFeO 3. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2020; 32:e2003711. [PMID: 32954556 DOI: 10.1002/adma.202003711] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Revised: 07/30/2020] [Indexed: 06/11/2023]
Abstract
Bismuth ferrite (BiFeO3 ) is one of the most widely studied multiferroics. The coexistence of ferroelectricity and antiferromagnetism in this compound has driven an intense search for electric-field control of the magnetic order. Such efforts require a complete understanding of the various exchange interactions that underpin the magnetic behavior. An important characteristic of BiFeO3 is its noncollinear magnetic order; namely, a long-period incommensurate spin cycloid. Here, the progress in understanding this fascinating aspect of BiFeO3 is reviewed, with a focus on epitaxial films. The advances made in developing the theory used to capture the complexities of the cycloid are first chronicled, followed by a description of the various experimental techniques employed to probe the magnetic order. To help the reader fully grasp the nuances associated with thin films, a detailed description of the spin cycloid in the bulk is provided. The effects of various perturbations on the cycloid are then described: magnetic and electric fields, doping, epitaxial strain, finite size effects, and temperature. To conclude, an outlook on possible device applications exploiting noncollinear magnetism in BiFeO3 films is presented. It is hoped that this work will act as a comprehensive experimentalist's guide to the spin cycloid in BiFeO3 thin films.
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Affiliation(s)
- Stuart R Burns
- School of Materials Science and Engineering, UNSW Sydney, High Street, Kensington, Sydney, 2052, Australia
- Department of Chemistry, University of Calgary, Calgary, AB, T2N 1N4, Canada
| | - Oliver Paull
- School of Materials Science and Engineering, UNSW Sydney, High Street, Kensington, Sydney, 2052, Australia
| | - Jean Juraszek
- Normandie University, UNIROUEN, INSA Rouen, CNRS, GPM, Rouen, 76000, France
| | - Valanoor Nagarajan
- School of Materials Science and Engineering, UNSW Sydney, High Street, Kensington, Sydney, 2052, Australia
| | - Daniel Sando
- School of Materials Science and Engineering, UNSW Sydney, High Street, Kensington, Sydney, 2052, Australia
- Mark Wainwright Analytical Centre, UNSW Sydney, High Street, Kensington, Sydney, 2052, Australia
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Davydova MD, Zvezdin KA, Mukhin AA, Zvezdin AK. Spin dynamics, antiferrodistortion and magnetoelectric interaction in multiferroics. The case of BiFeO3. PHYSICAL SCIENCES REVIEWS 2020. [DOI: 10.1515/psr-2019-0070] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
AbstractWe present a theoretical study of the spin dynamics in perovskite-like multiferroics with homogeneous magnetic order in the presence of external magnetic and electric fields. A particular example of such material is BeFeO3 in which the spin cycloid can be suppressed by application of external magnetic field, doping or by epitaxial strain. Understanding the effect of the external electric field on the spin-wave spectrum of these systems is required for devices based on spin wave interference and other innovative advances of magnonics and spintronics. Thus, we propose a model for BiFeO3 in which the thermodynamic potential is expressed in terms of polarization \boldsymbol{P}, antiferrodistortion \boldsymbol{\Omega}, antiferromagnetic moment \boldsymbol{L} and magnetization \boldsymbol{M}. Based on this model, we derive the corresponding equations of motion and demonstrate the existence of electromagnons, that is, magnons that can be excited by electric fields. These excitations are closely related to the magnetoelectric effect and the dynamics of the antiferrodistortion \boldsymbol{\Omega}. Specifically, the influence of the external electric field on the magnon spectra is due to reorientation of both polarization \boldsymbol{P} and antiferrodistortion \boldsymbol{\Omega} under the influence of the electric field and is linked to emergence of a field-induced anisotropy.
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Affiliation(s)
- M. D. Davydova
- Physics, Massachusetts Institute of Technology, 182 Memorial Dr, Cambridge, MA 02139-4307, USA
| | - K. A. Zvezdin
- Prokhorov General Physics Institute of the Russian Academy of Sciences, Moskva, Russian Federation
| | - A. A. Mukhin
- Prokhorov General Physics Institute of the Russian Academy of Sciences, 119991Moscow, Russia
| | - A. K. Zvezdin
- Prokhorov General Physics Institute of the Russian Academy of Sciences, Moskva, Russian Federation
- Faculty of Physics, National Research University Higher School of Economics, Moscow101000, Russia
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6
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Song Y, Xu B, Nan CW. Lattice and spin dynamics in multiferroic BiFeO 3 and RMnO 3. Natl Sci Rev 2019; 6:642-652. [PMID: 34691920 PMCID: PMC8291440 DOI: 10.1093/nsr/nwz055] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Revised: 04/03/2019] [Accepted: 04/10/2019] [Indexed: 11/17/2022] Open
Abstract
The multiferroic materials BiFeO3 and RMnO3 exhibit coexisting magnetic order and ferroelectricity, and provide exciting platforms for new physics and potentially novel devices, where intriguing interplay between phonons and magnons exists. In this review, we paint a complete picture of bulk BiFeO3 together with orthorhombic and hexagonal RMnO3 (R includes rare-earth elements and yttrium) by summarizing the dynamics of spin and lattice and their magnetoelectric coupling, as well as the methods of controlling these characteristics under non-equilibrium conditions, from experimental and simulation perspectives.
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Affiliation(s)
- Yan Song
- School of Materials Science and Engineering, and State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University, Beijing 100084, China
| | - Ben Xu
- School of Materials Science and Engineering, and State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University, Beijing 100084, China
| | - Ce-Wen Nan
- School of Materials Science and Engineering, and State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University, Beijing 100084, China
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7
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Sayedaghaee SO, Xu B, Prosandeev S, Paillard C, Bellaiche L. Novel Dynamical Magnetoelectric Effects in Multiferroic BiFeO_{3}. PHYSICAL REVIEW LETTERS 2019; 122:097601. [PMID: 30932533 DOI: 10.1103/physrevlett.122.097601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2018] [Revised: 01/19/2019] [Indexed: 06/09/2023]
Abstract
An atomistic effective Hamiltonian scheme is employed within molecular dynamics simulations to investigate how the electrical polarization and magnetization of the multiferroic BiFeO_{3} respond to time-dependent ac magnetic fields of various frequencies, as well as to reveal the frequency dependency of the dynamical (quadratic) magnetoelectric coefficient. We found the occurrence of vibrations having phonon frequencies in both the time dependency of the electrical polarization and magnetization (for any applied ac frequency), therefore making such vibrations of electromagnonic nature, when the homogeneous strain of the system is frozen (case 1). Moreover, the quadratic magnetoelectric coupling constant is monotonic and almost dispersionless in the sub-THz range in this case 1. In contrast, when the homogeneous strain can fully relax (case 2), two additional low-frequency and strain-mediated oscillations emerge in the time-dependent behavior of the polarization and magnetization, which result in resonances in the quadratic magnetoelectric coefficient. Such additional oscillations consist of a mixing between acoustic phonons, optical phonons, and magnons, and reflect the existence of a new quasiparticle that can be coined an "electroacoustic magnon." This latter finding can prompt experimentalists to shape their samples to take advantage of, and tune, the magnetostrictive-induced mechanical resonance frequency, in order to achieve large dynamical magnetoelectric couplings.
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Affiliation(s)
- S Omid Sayedaghaee
- Physics Department and Institute for Nanoscience and Engineering, University of Arkansas, Fayetteville, Arkansas 72701, USA
- Microelectronics-Photonics Program, University of Arkansas, Fayetteville, Arkansas 72701, USA
| | - Bin Xu
- Physics Department and Institute for Nanoscience and Engineering, University of Arkansas, Fayetteville, Arkansas 72701, USA
- School of Physical Science and Technology, Soochow University, Suzhou, Jiangsu 215006, China
| | - Sergey Prosandeev
- Physics Department and Institute for Nanoscience and Engineering, University of Arkansas, Fayetteville, Arkansas 72701, USA
- Institute of Physics and Physics Department of Southern Federal University, Rostov-na-Donu 344090, Russia
| | - Charles Paillard
- Physics Department and Institute for Nanoscience and Engineering, University of Arkansas, Fayetteville, Arkansas 72701, USA
- Laboratoire Structures, Propriétés et Modélisation des Solides, CentraleSupélec, CNRS UMR 8580, Université Paris-Saclay, 91190 Gif-sur-Yvette, France
| | - L Bellaiche
- Physics Department and Institute for Nanoscience and Engineering, University of Arkansas, Fayetteville, Arkansas 72701, USA
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Zheng Y, Chen WJ. Characteristics and controllability of vortices in ferromagnetics, ferroelectrics, and multiferroics. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2017; 80:086501. [PMID: 28155849 DOI: 10.1088/1361-6633/aa5e03] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Topological defects in condensed matter are attracting e significant attention due to their important role in phase transition and their fascinating characteristics. Among the various types of matter, ferroics which possess a switchable physical characteristic and form domain structure are ideal systems to form topological defects. In particular, a special class of topological defects-vortices-have been found to commonly exist in ferroics. They often manifest themselves as singular regions where domains merge in large systems, or stabilize as novel order states instead of forming domain structures in small enough systems. Understanding the characteristics and controllability of vortices in ferroics can provide us with deeper insight into the phase transition of condensed matter and also exciting opportunities in designing novel functional devices such as nano-memories, sensors, and transducers based on topological defects. In this review, we summarize the recent experimental and theoretical progress in ferroic vortices, with emphasis on those spin/dipole vortices formed in nanoscale ferromagnetics and ferroelectrics, and those structural domain vortices formed in multiferroic hexagonal manganites. We begin with an overview of this field. The fundamental concepts of ferroic vortices, followed by the theoretical simulation and experimental methods to explore ferroic vortices, are then introduced. The various characteristics of vortices (e.g. formation mechanisms, static/dynamic features, and electronic properties) and their controllability (e.g. by size, geometry, external thermal, electrical, magnetic, or mechanical fields) in ferromagnetics, ferroelectrics, and multiferroics are discussed in detail in individual sections. Finally, we conclude this review with an outlook on this rapidly developing field.
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Affiliation(s)
- Yue Zheng
- State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, Sun Yat-sen University, Guangzhou 510275, Guangdong, People's Republic of China. Micro&Nano Physics and Mechanics Research Laboratory, School of Physics, Sun Yat-sen University, Guangzhou 510275, Guangdong, People's Republic of China
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Boyn S, Grollier J, Lecerf G, Xu B, Locatelli N, Fusil S, Girod S, Carrétéro C, Garcia K, Xavier S, Tomas J, Bellaiche L, Bibes M, Barthélémy A, Saïghi S, Garcia V. Learning through ferroelectric domain dynamics in solid-state synapses. Nat Commun 2017; 8:14736. [PMID: 28368007 PMCID: PMC5382254 DOI: 10.1038/ncomms14736] [Citation(s) in RCA: 158] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Accepted: 01/26/2017] [Indexed: 11/09/2022] Open
Abstract
In the brain, learning is achieved through the ability of synapses to reconfigure the strength by which they connect neurons (synaptic plasticity). In promising solid-state synapses called memristors, conductance can be finely tuned by voltage pulses and set to evolve according to a biological learning rule called spike-timing-dependent plasticity (STDP). Future neuromorphic architectures will comprise billions of such nanosynapses, which require a clear understanding of the physical mechanisms responsible for plasticity. Here we report on synapses based on ferroelectric tunnel junctions and show that STDP can be harnessed from inhomogeneous polarization switching. Through combined scanning probe imaging, electrical transport and atomic-scale molecular dynamics, we demonstrate that conductance variations can be modelled by the nucleation-dominated reversal of domains. Based on this physical model, our simulations show that arrays of ferroelectric nanosynapses can autonomously learn to recognize patterns in a predictable way, opening the path towards unsupervised learning in spiking neural networks.
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Affiliation(s)
- Sören Boyn
- Unité Mixte de Physique, CNRS, Thales, Univ. Paris Sud, Université Paris-Saclay, Palaiseau 91767, France
| | - Julie Grollier
- Unité Mixte de Physique, CNRS, Thales, Univ. Paris Sud, Université Paris-Saclay, Palaiseau 91767, France
| | - Gwendal Lecerf
- University of Bordeaux, IMS, UMR 5218, Talence F-33405, France
| | - Bin Xu
- Department of Physics and Institute for Nanoscience and Engineering, University of Arkansas Fayetteville, Arkansas 72701, USA
| | - Nicolas Locatelli
- Centre de Nanosciences et de Nanotechnologies, CNRS, Univ. Paris Sud, Université Paris-Saclay, C2N-Orsay, Orsay cedex 91405, France
| | - Stéphane Fusil
- Unité Mixte de Physique, CNRS, Thales, Univ. Paris Sud, Université Paris-Saclay, Palaiseau 91767, France
| | - Stéphanie Girod
- Unité Mixte de Physique, CNRS, Thales, Univ. Paris Sud, Université Paris-Saclay, Palaiseau 91767, France
| | - Cécile Carrétéro
- Unité Mixte de Physique, CNRS, Thales, Univ. Paris Sud, Université Paris-Saclay, Palaiseau 91767, France
| | - Karin Garcia
- Unité Mixte de Physique, CNRS, Thales, Univ. Paris Sud, Université Paris-Saclay, Palaiseau 91767, France
| | - Stéphane Xavier
- Thales Research and Technology, 1 Avenue Augustin Fresnel, Campus de I'Ecole Polytechnique, Palaiseau 91767, France
| | - Jean Tomas
- University of Bordeaux, IMS, UMR 5218, Talence F-33405, France
| | - Laurent Bellaiche
- Department of Physics and Institute for Nanoscience and Engineering, University of Arkansas Fayetteville, Arkansas 72701, USA
| | - Manuel Bibes
- Unité Mixte de Physique, CNRS, Thales, Univ. Paris Sud, Université Paris-Saclay, Palaiseau 91767, France
| | - Agnès Barthélémy
- Unité Mixte de Physique, CNRS, Thales, Univ. Paris Sud, Université Paris-Saclay, Palaiseau 91767, France
| | - Sylvain Saïghi
- University of Bordeaux, IMS, UMR 5218, Talence F-33405, France
| | - Vincent Garcia
- Unité Mixte de Physique, CNRS, Thales, Univ. Paris Sud, Université Paris-Saclay, Palaiseau 91767, France
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Wang D, Bokov AA, Ye ZG, Hlinka J, Bellaiche L. Subterahertz dielectric relaxation in lead-free Ba(Zr,Ti)O3 relaxor ferroelectrics. Nat Commun 2016; 7:11014. [PMID: 27040174 PMCID: PMC4822000 DOI: 10.1038/ncomms11014] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2015] [Accepted: 02/11/2016] [Indexed: 11/09/2022] Open
Abstract
Relaxors are complex materials with unusual properties that have been puzzling the scientific community since their discovery. The main characteristic of relaxors, that is, their dielectric relaxation, remains unclear and is still under debate. The difficulty to conduct measurements at frequencies ranging from ≃1 GHz to ≃1 THz and the challenge of developing models to capture their complex dynamical responses are among the reasons for such a situation. Here, we report first-principles-based molecular dynamic simulations of lead-free Ba(Zr0.5Ti0.5)O3, which allows us to obtain its subterahertz dynamics. This approach reproduces the striking characteristics of relaxors including the dielectric relaxation, the constant-loss behaviour, the diffuse maximum in the temperature dependence of susceptibility, the substantial widening of dielectric spectrum on cooling and the resulting Vogel-Fulcher law. The simulations further relate such features to the decomposed dielectric responses, each associated with its own polarization mechanism, therefore, enhancing the current understanding of relaxor behaviour.
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Affiliation(s)
- D Wang
- Electronic Materials Research Laboratory-Key Laboratory of the Ministry of Education and International Center for Dielectric Research, School of Electronic and Information Engineering, Xi'an Jiaotong University, No. 28, Xianning West Road, Xi'an 710049, China
| | - A A Bokov
- Department of Chemistry and 4D LABS, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1A6
| | - Z-G Ye
- Electronic Materials Research Laboratory-Key Laboratory of the Ministry of Education and International Center for Dielectric Research, School of Electronic and Information Engineering, Xi'an Jiaotong University, No. 28, Xianning West Road, Xi'an 710049, China.,Department of Chemistry and 4D LABS, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1A6
| | - J Hlinka
- Department of Dielectrics, The Czech Academy of Sciences, Na Slovance 2, CZ-182 21 Praha 8, Czech Republic
| | - L Bellaiche
- Department of Physics and Institute for Nanoscience and Engineering, University of Arkansas, Fayetteville, Arkansas 72701, USA
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11
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Buhot J, Toulouse C, Gallais Y, Sacuto A, de Sousa R, Wang D, Bellaiche L, Bibes M, Barthélémy A, Forget A, Colson D, Cazayous M, Measson MA. Driving Spin Excitations by Hydrostatic Pressure in BiFeO(3). PHYSICAL REVIEW LETTERS 2015; 115:267204. [PMID: 26765020 DOI: 10.1103/physrevlett.115.267204] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Indexed: 06/05/2023]
Abstract
Optical spectroscopy has been combined with computational and theoretical techniques to show how the spin dynamics in the model multiferroic BiFeO(3) responds to the application of hydrostatic pressure and its corresponding series of structural phase transitions from R3c to the Pnma phases. As pressure increases, multiple spin excitations associated with noncollinear cycloidal magnetism collapse into two excitations, which show jump discontinuities at some of the ensuing crystal phase transitions. The effective Hamiltonian approach provides information on the electrical polarization and structural changes of the oxygen octahedra through the successive structural phases. The extracted parameters are then used in a Ginzburg-Landau model to reproduce the evolution with pressure of the spin wave excitations observed at low energy, and we demonstrate that the structural phases and the magnetic anisotropy drive and control the spin excitations.
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Affiliation(s)
- J Buhot
- Laboratoire Matériaux et Phénomènes Quantiques, UMR 7162 CNRS, Université Paris Diderot, Bâtiment Condorcet 75205 Paris Cedex 13, France
| | - C Toulouse
- Laboratoire Matériaux et Phénomènes Quantiques, UMR 7162 CNRS, Université Paris Diderot, Bâtiment Condorcet 75205 Paris Cedex 13, France
| | - Y Gallais
- Laboratoire Matériaux et Phénomènes Quantiques, UMR 7162 CNRS, Université Paris Diderot, Bâtiment Condorcet 75205 Paris Cedex 13, France
| | - A Sacuto
- Laboratoire Matériaux et Phénomènes Quantiques, UMR 7162 CNRS, Université Paris Diderot, Bâtiment Condorcet 75205 Paris Cedex 13, France
| | - R de Sousa
- Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia, Canada, V8W 2Y2
| | - D Wang
- Electronic Materials Research Laboratory-Key Laboratory of the Ministry of Education, and International Center for Dielectric Research, Xi'an Jiaotong University, Xi'an 710049, China
| | - L Bellaiche
- Physics Department and Institute for Nanoscience and Engineering, University of Arkansas, Fayetteville, Arkansas 72701, USA
| | - M Bibes
- Unité Mixte de Physique CNRS/Thales, 1 avenue Augustin Fresnel, Campus de l'Ecole Polytechnique, F-91767 Palaiseau, France et Université Paris-Sud, 91405 Orsay, France
| | - A Barthélémy
- Unité Mixte de Physique CNRS/Thales, 1 avenue Augustin Fresnel, Campus de l'Ecole Polytechnique, F-91767 Palaiseau, France et Université Paris-Sud, 91405 Orsay, France
| | - A Forget
- Service de Physique de l'Etat Condensé, CEA Saclay, IRAMIS, SPEC (CNRS URA 2464), F-91191 Gif sur Yvette, France
| | - D Colson
- Service de Physique de l'Etat Condensé, CEA Saclay, IRAMIS, SPEC (CNRS URA 2464), F-91191 Gif sur Yvette, France
| | - M Cazayous
- Laboratoire Matériaux et Phénomènes Quantiques, UMR 7162 CNRS, Université Paris Diderot, Bâtiment Condorcet 75205 Paris Cedex 13, France
| | - M-A Measson
- Laboratoire Matériaux et Phénomènes Quantiques, UMR 7162 CNRS, Université Paris Diderot, Bâtiment Condorcet 75205 Paris Cedex 13, France
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Park JG, Le MD, Jeong J, Lee S. Structure and spin dynamics of multiferroic BiFeO3. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:433202. [PMID: 25299241 DOI: 10.1088/0953-8984/26/43/433202] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Multiferroic materials have attracted much interest due to the unusual coexistence of ferroelectric and (anti-)ferromagnetic ground states in a single compound. They offer an exciting platform for new physics and potentially novel devices. BiFeO3 is one of the most celebrated multiferroic materials and has highly desirable properties. It is the only known room-temperature multiferroic with TC ≈ 1100 K and TN ≈ 650 K, and exhibits one of the largest spontaneous electric polarisations, P ≈ 80 µC cm(-2). At the same time, it has a magnetic cycloid structure with an extremely long period of 620 Å, which arises from competition between the usual symmetric exchange interaction and the antisymmetric Dzyaloshinskii-Moriya (DM) interaction. There is also an intriguing interplay between the DM interaction and single ion anisotropy K. In this review, we have attempted to paint a complete picture of bulk BiFeO3 by summarising the structural and dynamic properties of both the spin and lattice parts and their magneto-electric coupling.
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Affiliation(s)
- Je-Geun Park
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 151-747, Korea. Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea
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McCash K, Mani BK, Chang CM, Ponomareva I. The role of mechanical boundary conditions in the soft mode dynamics of PbTiO3. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:435901. [PMID: 25299708 DOI: 10.1088/0953-8984/26/43/435901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The role of different mechanical boundary conditions in the soft mode dynamics of ferroelectric PbTiO3 is systematically investigated using first-principles-based simulations and analytical model. The change in the soft mode dynamics due to hydrostatic pressure, uniaxial and biaxial stresses and biaxial strains is studied in a wide temperature range. Our computations predict: (i) the existence of Curie-Weiss laws that relate the soft mode frequency to the stress or strain; (ii) a non-trivial temperature evolution of the associated Curie-Weiss constants; (iii) a qualitative difference between the soft mode response to stresses/strains and hydrostatic pressure. The latter finding implies that the Curie-Weiss pressure law commonly used for residual stress estimation may not apply for the cases of uniaxial and biaxial stresses and strains. On the other hand, our systematic study offers a way to eliminate this difficulty through the establishment of Curie-Weiss stress and strain laws. Implications of our predictions for some available experimental data are discussed.
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Affiliation(s)
- Kevin McCash
- Department of Physics, University of South Florida, Tampa, FL 33620, USA
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Bhattacharjee S, Rahmedov D, Wang D, Iñiguez J, Bellaiche L. Ultrafast switching of the electric polarization and magnetic chirality in BiFeO3 by an electric field. PHYSICAL REVIEW LETTERS 2014; 112:147601. [PMID: 24766014 DOI: 10.1103/physrevlett.112.147601] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2013] [Indexed: 06/03/2023]
Abstract
Using a first-principles-based effective Hamiltonian within molecular dynamics simulations, we discover that applying an electric field that is opposite to the initial direction of the polarization results in a switching of both the polarization and the magnetic chirality vector of multiferroic BiFeO3 at an ultrafast pace (namely, of the order of picoseconds). We discuss the origin of such a double ultrafast switching, which is found to involve original intermediate magnetic states and may hold promise for designing various devices.
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Affiliation(s)
- Satadeep Bhattacharjee
- Department of Physics and Institute for Nanoscience and Engineering, University of Arkansas Fayetteville, Arkansas 72701, USA
| | - Dovran Rahmedov
- Department of Physics and Institute for Nanoscience and Engineering, University of Arkansas Fayetteville, Arkansas 72701, USA
| | - Dawei Wang
- Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education and International Center for Dielectric Research, Xi'an Jiaotong University, Xi'an 710049, China
| | - Jorge Iñiguez
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, 08193 Bellaterra, Spain
| | - L Bellaiche
- Department of Physics and Institute for Nanoscience and Engineering, University of Arkansas Fayetteville, Arkansas 72701, USA
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Sando D, Agbelele A, Rahmedov D, Liu J, Rovillain P, Toulouse C, Infante IC, Pyatakov AP, Fusil S, Jacquet E, Carrétéro C, Deranlot C, Lisenkov S, Wang D, Le Breton JM, Cazayous M, Sacuto A, Juraszek J, Zvezdin AK, Bellaiche L, Dkhil B, Barthélémy A, Bibes M. Crafting the magnonic and spintronic response of BiFeO3 films by epitaxial strain. NATURE MATERIALS 2013; 12:641-6. [PMID: 23624631 DOI: 10.1038/nmat3629] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2012] [Accepted: 03/12/2013] [Indexed: 05/05/2023]
Abstract
Multiferroics are compounds that show ferroelectricity and magnetism. BiFeO3, by far the most studied, has outstanding ferroelectric properties, a cycloidal magnetic order in the bulk, and many unexpected virtues such as conductive domain walls or a low bandgap of interest for photovoltaics. Although this flurry of properties makes BiFeO3 a paradigmatic multifunctional material, most are related to its ferroelectric character, and its other ferroic property--antiferromagnetism--has not been investigated extensively, especially in thin films. Here we bring insight into the rich spin physics of BiFeO3 in a detailed study of the static and dynamic magnetic response of strain-engineered films. Using Mössbauer and Raman spectroscopies combined with Landau-Ginzburg theory and effective Hamiltonian calculations, we show that the bulk-like cycloidal spin modulation that exists at low compressive strain is driven towards pseudo-collinear antiferromagnetism at high strain, both tensile and compressive. For moderate tensile strain we also predict and observe indications of a new cycloid. Accordingly, we find that the magnonic response is entirely modified, with low-energy magnon modes being suppressed as strain increases. Finally, we reveal that strain progressively drives the average spin angle from in-plane to out-of-plane, a property we use to tune the exchange bias and giant-magnetoresistive response of spin valves.
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Affiliation(s)
- D Sando
- Unité Mixte de Physique CNRS/Thales, 1 av. Fresnel, 91767 Palaiseau & Université Paris-Sud, 91405 Orsay, France
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