Flexoelectric Effect in Solids

Zubko, Pavlo; Catalán, Gustau; Tagantsev, A. K.

doi:10.1146/annurev-matsci-071312-121634

Cited by 883 publications

(749 citation statements)

References 135 publications

(135 reference statements)

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“…Meanwhile, generally, the mechanical boundary conditions should be modified as well [23,53]. The modified mechanical boundary conditions were recently derived by Yurkov [53] 12 . It has been shown that such a modification is not needed for the case where the polarization vanishes at the surface.…”

Section: General Casementioning

confidence: 99%

Fundamentals of flexoelectricity in solids

2013

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The flexoelectric effect is the response of electric polarization to a mechanical strain gradient. It can be viewed as a higher-order effect with respect to piezoelectricity, which is the response of polarization to strain itself. However, at the nanoscale, where large strain gradients are expected, the flexoelectric effect becomes appreciable. Besides, in contrast to the piezoelectric effect, flexoelectricity is allowed by symmetry in any material. Due to these qualities flexoelectricity has attracted growing interest during the past decade. Presently, its role in the physics of dielectrics and semiconductors is widely recognized and the effect is viewed as promising for practical applications. On the other hand, the available theoretical and experimental results are rather contradictory, attesting to a limited understanding in the field. This review paper presents a critical analysis of the current knowledge on the flexoelectricity in common solids, excluding organic materials and liquid crystals.

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Section: General Casementioning

confidence: 99%

Fundamentals of flexoelectricity in solids

2013

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“…In particular, strain-engineering of multiferroism has opened a path for the exploration of new phases with improved properties compared to their bulk parents [10][11][12][13][14] Recently, the coupling between strain gradients and polarization, known as flexoelectricity 15 , has been analyzed intensely due to its remarkable contribution to the polarization and permittivity of inhomogeneously strained ferroelectrics [16][17][18][19][20][21] . The most dramatic manifestations of flexoelectricity have been reported in thin films, as it is an inherently size-dependent 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 5 phenomenon where strain gradients are inversely proportional to size 19,20,22 .…”

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confidence: 99%

Polar-Graded Multiferroic SrMnO₃ Thin Films

et al. 2016

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Engineering defects and strains in oxides provides a promising route for the quest of thin film materials with coexisting ferroic orders, multiferroics, with efficient magnetoelectric coupling at room temperature. Precise control of the strain gradient would enable custom tailoring of the multiferroic properties, but presently remains challenging. Here we explore the existence of a polar-graded state in epitaxially-strained antiferromagnetic SrMnO 3 thin films, whose polar nature was predicted theoretically, and recently demonstrated experimentally. By means of aberration-corrected scanning transmission electron microscopy we map the polar rotation of the ferroelectric polarization at atomic resolution, both far from and near the domain walls and find flexoelectricity resulting from vertical strain gradients. The origin of this particular strain state is a gradual distribution of oxygen vacancies across the film thickness, according to electron energy loss spectroscopy. Herein we present a chemistry-mediated route to induce polar rotations in oxygen-deficient multiferroic films, resulting in flexoelectric polar rotations and with potentially enhanced piezoelectricity. KEYWORDS: Multiferroics, ferroelectricity, flexoelectricity, aberration-corrected STEM, domain walls. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 4 TEXT Multiferroic materials have attracted great interest recently because of their intriguing fundamental physics and the wide range of potential applications such as transducers and information storage [1][2][3] . Of particular technological impact is the search for materials showing efficient coupling between ferromagnetic and ferroelectric orders that persist at room temperature. Manganese-based perovskite oxides AMnO 3 , A being an alkaline-earth cation, are particularly promising for this purpose; theoretical calculations reveal the onset of a ferroelectric ground state with strong magnetoelectric coupling since the spontaneous polarization is expected to be driven by the off-centering of the magnetic Mn 4+ ion 4,5 . The ferroelectric instability is predicted to increase by expansion of the lattice and, in turn, strain-induced ferroelectricity was experimentally demonstrated in Ba-substituted SrMnO 3 single crystals, in which chemical expansion of the crystal lattice is caused by partially replacing Sr with larger Ba ions 6 .Alternatively, strains can be induced into films through the use of epitaxial growth and can be utilized to modify the ferroelectric film properties by an adequate choice of the substrate 7-9 . In particular, strain-engineering of multiferroism has opened a path for the e...

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“…This chapter introduces the fundamental physics and concepts of dielectrics [30][31][32][33][34][35][36][37][38][39] and their classification [38][39][40][41][42][43][44][45][46] , as well as of ferroelectrics 2,16,29,[37][38][39][40][41][42][43][44][45][46][47][48][49][50] , and relaxor ferroelectrics. [51][52][53][54][55][56][57] The information of many textbooks and review papers related to the physics of materials science was employed throughout these sections.…”

Section: Theoretical Backgroundmentioning

confidence: 99%

Strain Mechanisms in Lead-Free Ferroelectrics for Actuators

Acosta

2016

Springer Theses

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Flexoelectric Effect in Solids

Cited by 883 publications

References 135 publications

Fundamentals of flexoelectricity in solids

Fundamentals of flexoelectricity in solids

Polar-Graded Multiferroic SrMnO₃ Thin Films

Strain Mechanisms in Lead-Free Ferroelectrics for Actuators

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Flexoelectric Effect in Solids

Cited by 883 publications

References 135 publications

Fundamentals of flexoelectricity in solids

Fundamentals of flexoelectricity in solids

Polar-Graded Multiferroic SrMnO3 Thin Films

Strain Mechanisms in Lead-Free Ferroelectrics for Actuators

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Polar-Graded Multiferroic SrMnO₃ Thin Films