Ferroelectricity and Self-Polarization in Ultrathin Relaxor Ferroelectric Films

Miao, Peixian; Zhao, Yonggang; Luo, Nengneng; Zhao, Diyang; Chen, Aitian; Sun, Zhong; Guo, Meiqi; Zhu, M. H.; Zhang, Huiyun; Liu, Qiang

doi:10.1038/srep19965

Cited by 36 publications

(20 citation statements)

References 41 publications

(81 reference statements)

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“…A similar increase of T max and decrease of ΔT disp has been previously reported as a result of compressive strain in relaxor thin films [30][31][32], and has been related to changes of the correlation length and polar nanoregion morphology, and the direction of dipoles within them [30][31][32][33][34]. To examine whether defect-induced changes in the morphology of the local-polar order are responsible for the weakening of the relaxor response, a series of twodimensional reciprocal space mapping studies was conducted (Supplemental Material, Figs.…”

supporting

confidence: 86%

Defect-Induced (Dis)Order in Relaxor Ferroelectric Thin Films

et al. 2019

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The effect of intrinsic point defects on relaxor properties of 0.68 PbMg 1=3 Nb 2=3 O 3-0.32 PbTiO 3 thin films is studied across nearly 2 orders of magnitude of defect concentration via ex post facto ion bombardment. A weakening of the relaxor character is observed with increasing concentration of bombardment-induced point defects, which is hypothesized to be related to strong interactions between defect dipoles and the polarization. Although more defects and structural disorder are introduced in the system as a result of ion bombardment, the special type of defects that are likely to form in these polar materials (i.e., defect dipoles) can stabilize the direction of polarization against thermal fluctuations, and in turn, weaken relaxor behavior.

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confidence: 86%

Defect-Induced (Dis)Order in Relaxor Ferroelectric Thin Films

et al. 2019

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“…While the use of epitaxial constraints to manipulate ferroelectric order has been widely demonstrated, [25][26][27] little of that work has focused on relaxors. [28][29][30][31][32] Theoretical studies have proposed that strain can significantly alter the morphologies of local-polar order and the direction of dipoles within them. [28] But experimental studies have provided contradicting observations of the effect of epitaxial strain [29][30][31][32] ; some suggest that compressive strain increases T m [29,30] and induces ferroelectricity [31] while others claim that compressive strain decreases T m and favors the relaxor state.…”

mentioning

confidence: 99%

“…[28][29][30][31][32] Theoretical studies have proposed that strain can significantly alter the morphologies of local-polar order and the direction of dipoles within them. [28] But experimental studies have provided contradicting observations of the effect of epitaxial strain [29][30][31][32] ; some suggest that compressive strain increases T m [29,30] and induces ferroelectricity [31] while others claim that compressive strain decreases T m and favors the relaxor state. [32] These discrepancies likely arise from the use of partially relaxed (i.e., inhomogeneously strained) films [33] and from insufficient study of essential relaxor characteristics (e.g., local correlations and dynamics, diffuse-scattering, frequency dispersion of T m , etc.).…”

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confidence: 99%

Epitaxial Strain Control of Relaxor Ferroelectric Phase Evolution

Kim

Takenaka

et al. 2019

Advanced Materials

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Alternatively, molecular-dynamics (MD) simulations have shown that relaxors can be interpreted as exhibiting a multidomain state without a nonpolar matrix (i.e., polar nanodomains or PNDs). [4] The exact nature of order in relaxors, however, remains an ongoing debate [5] and, in turn, new approaches to study these complex materials are required to further illuminate the structure and how it can be controlled and can impact material properties. [5-9] In any case, it is essential to understand the evolution of the polar structure in relaxors (be they PNRs or PNDs) under applied stimuli as these are key to understanding relaxor behavior and large electromechanical effects in relaxors. Over the years, X-ray and neutron diffuse-scattering measurements have emerged as an essential tool to study the structural signatures of relaxor behavior [10-19] and studies on single-crystal relaxors have investigated the evolution of polar regions/domains (e.g., size, morphology) and suggested that they alter their size [14-17] and orientation [18] under different external stimuli. For example, under applied electric fields, which were expected to enhance polar order, the local order was found to align perpendicular to the field [18] and induce an asymmetry in the lattice dynamics [19] that could ultimately be responsible for the large electromechanical effects. [20] Other studies used pressure to push the material in the opposite directionto destabilize polar order [17]-and even induce a crossover from Understanding and ultimately controlling the large electromechanical effects in relaxor ferroelectrics requires intimate knowledge of how the local-polar order evolves under applied stimuli. Here, the biaxial-strain-induced evolution of and correlations between polar structures and properties in epitaxial films of the prototypical relaxor ferroelectric 0.68PbMg 1/3 Nb 2/3 O 3-0.32PbTiO 3 are investigated. X-ray diffuse-scattering studies reveal an evolution from a butterfly-to disc-shaped pattern and an increase in the correlation-length from ≈8 to ≈25 nm with increasing compressive strain. Molecular-dynamics simulations reveal the origin of the changes in the diffuse-scattering patterns and that strain induces polarization rotation and the merging of the polar order. As the magnitude of the strain is increased, relaxor behavior is gradually suppressed but is not fully quenched. Analysis of the dynamic evolution of dipole alignment in the simulations reveals that, while, for most unit-cell chemistries and configurations, strain drives a tendency toward more ferroelectric-like order, there are certain unit cells that become more disordered under strain, resulting in stronger competition between ordered and disordered regions and enhanced overall susceptibilities. Ultimately, this implies that deterministic creation of specific local chemical configurations could be an effective way to enhance relaxor performance.

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“…[10][11][12][13][14][15] Despite the great attention received by PMN-PT in thin lm form, in particular for energy harvesting, energy storage and cooling applications, [16][17][18][19][20][21] there is still a lack of knowledge regarding epitaxial thin lms, particularly concerning correlations between the local atomic structure/strain and physical properties. 10,[22][23][24][25][26][27] Thus, understanding of the domains in relaxor ferroelectric thin lms and their evolution under external parameters such as epitaxial strain is crucial for practical applications. While strain engineering in ferroelectric and multiferroic thin lms is known to be a powerful route to control, tune, and enhance the functional properties and also create/induce new exotic properties that do not exist in bulk, [28][29][30] few studies have been done on the effect of strain in relaxor ferroelectrics.…”

Section: Introductionmentioning

confidence: 99%

“…While strain engineering in ferroelectric and multiferroic thin lms is known to be a powerful route to control, tune, and enhance the functional properties and also create/induce new exotic properties that do not exist in bulk, [28][29][30] few studies have been done on the effect of strain in relaxor ferroelectrics. 10,23,31,32 Note that control of the epitaxial strain at the atomic level and the profound understanding of its effect on the structural characteristics require samples of high quality, free from inactive pyrochlore phases. However, due to the compositional complexity of PMN-PT, the synthesis of pyrochlore free phases is known to be challenging.…”

Section: Introductionmentioning

confidence: 99%