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Stengel M. Macroscopic Polarization from Nonlinear Gradient Couplings. PHYSICAL REVIEW LETTERS 2024; 132:146801. [PMID: 38640360 DOI: 10.1103/physrevlett.132.146801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2023] [Accepted: 02/14/2024] [Indexed: 04/21/2024]
Abstract
We show that a lattice mode of arbitrary symmetry induces a well-defined macroscopic polarization at first order in the momentum and second order in the amplitude. We identify a symmetric flexoelectric-like contribution, which is sensitive to both the electrical and mechanical boundary conditions, and an antisymmetric Dzialoshinskii-Moriya-like term, which is unaffected by either. We develop the first-principles methodology to compute the relevant coupling tensors in an arbitrary crystal, which we illustrate with the example of the antiferrodistortive order parameter in SrTiO_{3}.
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Affiliation(s)
- Massimiliano Stengel
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, 08193 Bellaterra, Spain and ICREA-Institució Catalana de Recerca i Estudis Avançats, 08010 Barcelona, Spain
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Morozovska AN, Khist VV, Glinchuk MD, Scherbakov CM, Silibin MV, Karpinsky DV, Eliseev EA. Flexoelectricity induced spatially modulated phases in ferroics and liquid crystals. J Mol Liq 2018. [DOI: 10.1016/j.molliq.2018.01.052] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Zhang Q, Xie L, Liu G, Prokhorenko S, Nahas Y, Pan X, Bellaiche L, Gruverman A, Valanoor N. Nanoscale Bubble Domains and Topological Transitions in Ultrathin Ferroelectric Films. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2017; 29:1702375. [PMID: 29064154 DOI: 10.1002/adma.201702375] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Revised: 07/10/2017] [Indexed: 06/07/2023]
Abstract
Observation of a new type of nanoscale ferroelectric domains, termed as "bubble domains"-laterally confined spheroids of sub-10 nm size with local dipoles self-aligned in a direction opposite to the macroscopic polarization of a surrounding ferroelectric matrix-is reported. The bubble domains appear in ultrathin epitaxial PbZr0.2 Ti0.8 O3 /SrTiO3 /PbZr0.2 Ti0.8 O3 ferroelectric sandwich structures due to the interplay between charge and lattice degrees of freedom. The existence of the bubble domains is revealed by high-resolution piezoresponse force microscopy (PFM), and is corroborated by aberration-corrected atomic-resolution scanning transmission electron microscopy mapping of the polarization displacements. An incommensurate phase and symmetry breaking is found within these domains resulting in local polarization rotation and hence impart a mixed Néel-Bloch-like character to the bubble domain walls. PFM hysteresis loops for the bubble domains reveal that they undergo an irreversible phase transition to cylindrical domains under the electric field, accompanied by a transient rise in the electromechanical response. The observations are in agreement with ab-initio-based calculations, which reveal a very narrow window of electrical and elastic parameters that allow the existence of bubble domains. The findings highlight the richness of polar topologies possible in ultrathin ferroelectric structures and bring forward the prospect of emergent functionalities due to topological transitions.
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Affiliation(s)
- Qi Zhang
- School of Materials Science and Engineering, The University of New South Wales, Sydney, New South Wales, 2052, Australia
| | - Lin Xie
- National Laboratory of Solid State Microstructures and Department of Materials Science and Engineering, Nanjing University, Nanjing, 210093, P. R. China
- Department of Chemical Engineering and Materials Science, University of California, Irvine, CA, 92697, USA
| | - Guangqing Liu
- School of Materials Science and Engineering, The University of New South Wales, Sydney, New South Wales, 2052, Australia
| | - Sergei Prokhorenko
- Theoretical Materials Physics Q-MAT CESAM, University of Liège, Sart Tilman, B-4000, Belgium
- Physics Department and Institute for Nanoscience and Engineering, University of Arkansas, Fayetteville, AR, 72701, USA
| | - Yousra Nahas
- Physics Department and Institute for Nanoscience and Engineering, University of Arkansas, Fayetteville, AR, 72701, USA
| | - Xiaoqing Pan
- Department of Chemical Engineering and Materials Science, University of California, Irvine, CA, 92697, USA
- Department of Physics and Astronomy, University of California, Irvine, CA, 92697, USA
| | - Laurent Bellaiche
- Physics Department and Institute for Nanoscience and Engineering, University of Arkansas, Fayetteville, AR, 72701, USA
| | - Alexei Gruverman
- Department of Physics and Astronomy, University of Nebraska, Lincoln, NE, 68588, USA
| | - Nagarajan Valanoor
- School of Materials Science and Engineering, The University of New South Wales, Sydney, New South Wales, 2052, Australia
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Peters JJP, Apachitei G, Beanland R, Alexe M, Sanchez AM. Polarization curling and flux closures in multiferroic tunnel junctions. Nat Commun 2016; 7:13484. [PMID: 27848970 PMCID: PMC5116095 DOI: 10.1038/ncomms13484] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Accepted: 10/03/2016] [Indexed: 11/10/2022] Open
Abstract
Formation of domain walls in ferroelectrics is not energetically favourable in low-dimensional systems. Instead, vortex-type structures are formed that are driven by depolarization fields occurring in such systems. Consequently, polarization vortices have only been experimentally found in systems in which these fields are deliberately maximized, that is, in films between insulating layers. As such configurations are devoid of screening charges provided by metal electrodes, commonly used in electronic devices, it is wise to investigate if curling polarization structures are innate to ferroelectricity or induced by the absence of electrodes. Here we show that in unpoled Co/PbTiO3/(La,Sr)MnO3 ferroelectric tunnel junctions, the polarization in active PbTiO3 layers 9 unit cells thick forms Kittel-like domains, while at 6 unit cells there is a complex flux-closure curling behaviour resembling an incommensurate phase. Reducing the thickness to 3 unit cells, there is an almost complete loss of switchable polarization associated with an internal gradient. Ferroelectric vortex-type structures have only been seen in isolated films, leaving electrode effects unexplored. Here, Peters et al. show that the polarisation curling and formation of vortex and flux-closure structures is a generic effect appearing in ultrathin ferroelectric films.
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Affiliation(s)
- Jonathan J P Peters
- Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
| | - Geanina Apachitei
- Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
| | - Richard Beanland
- Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
| | - Marin Alexe
- Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
| | - Ana M Sanchez
- Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
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