X-Ray investigations of the crystal structure and phase transitions of YMnO<sub>3</sub>

Łukaszewicz, K.; Karut-Kalicińska, Jarosława

doi:10.1080/00150197408237954

Cited by 95 publications

(71 citation statements)

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“…The temperatures of the high temperature phase transitions in hexagonal YMnO 3 have been the subject of much debate [3,14,[19][20][21][22][23]. A symmetry analysis [15,24,25] shows that there are three possible paths from the high temperature P6 3 /mmc phase to the room temperature ferroelectric P6 3 cm phase, summarized in figure 1.…”

Section: Introductionmentioning

confidence: 99%

Elastic anomalies associated with structural and magnetic phase transitions in single crystal hexagonal YMnO₃

Thomson

Chatterji

Howard

et al. 2014

J. Phys.: Condens. Matter

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Resonant ultrasound spectroscopy has been used to measure the elastic and anelastic behaviour through known structural and magnetic phase transitions in single crystal hexagonal YMnO 3 . Anomalous elastic behaviour is observed at the high temperature structural transition at ∼1260 K, with a discontinuity in the elastic constants and nonlinear recovery below T c , consistent with λeQ 2 s coupling. There is no change in dissipation associated with this high temperature transition, and no evidence in the elastic or anelastic behaviour for any secondary transition at ∼920 K, thus supporting the thesis of a single high temperature transformation. Elastic stiffening is observed on cooling through T N , in accordance with previous studies, and the excess elastic constant appears to scale with the square of the magnetic order parameter. The strains incurred at T N are a factor of ∼20 smaller than those at the structural transition, implying very weak λeQ 2 m coupling and a dominant contribution to the variation in the elastic constants from λe 2 Q 2 m . The increased acoustic dissipation above T N is consistent with an order-disorder process.

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Section: Introductionmentioning

confidence: 99%

Elastic anomalies associated with structural and magnetic phase transitions in single crystal hexagonal YMnO₃

Thomson

Chatterji

Howard

et al. 2014

J. Phys.: Condens. Matter

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“…After there has been some debate concerning the thermodynamic path occurring at the transition between the paraelectric P 6 3 /mmc (Z=2) and ferroelectric P 6 3 cm (Z=6) phases in YMnO 3 recent experimental and theoretical investigations agree in that the cell-tripled improper ferroelectric structure arises directly at the Curie temperature T C of about 1260 K. [1][2][3][4][5][6][7][8][9] A confirmation of this direct path is the observation of a ferroelectric domain pattern below T C consistent with the twodimensional-order-parameter symmetry associated with the K 3 zone-boundary phonon mode at k = ( 1 3 , 1 3 , 0). [10][11][12][13][14][15][16] The corresponding symmetry-breaking mechanism gives rise to a total of six domain states.…”

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Combinatorial model for the ferroelectric domain-network formation in hexagonal manganites

et al. 2014

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As the result of the high-temperature improper ferroelectric transition occurring in YMnO3 and other hexagonal manganites a striking domain pattern was observed: an emergence of six domains of alternating polarization from one point in a vortex-like pattern. We derive the formation and distribution of the domain-vortex network from a combinatorial analysis based on order-parameter symmetry and lattice geometry. The analysis leads to stable vortex-like configurations of the six domain states in the basal plane perpendicular to the polarization and to fragmented vortices in planes parallel to the polarization. The predictions are debated in the light of existing experimental and theoretical work on the vortex domain state. The relation of the symmetry-determined geometrical defects to the topological defects proposed to describe the behavior of YMnO3 near the Curie temperature is discussed.

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“…We use hexagonal YMnO 3 [17,18,19,20], which was recently predicted [21] and subsequently experimentally confirmed [22,23] to display an improper ferroelectric transition as an example. We investigate the intrinsic properties of isolated thin films of YMnO 3 with (0001) orientation and a clean oxygen terminated surface in the absence of an external field or electrode and determine the influence of the surface on the ferroelectric state.…”

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Absence of Critical Thickness in an Ultrathin Improper Ferroelectric Film

2009

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We study the ferroelectric stability and surface structural properties of an oxygen-terminated hexagonal YMnO3 ultra-thin film using density functional theory. Under an open circuit boundary condition, the ferroelectric state with the spontaneous polarization normal to the (0001) surface, is found to be metastable in a single domain state despite the presence of a depolarizing field. We establish a connection between the result and the role of improper ferroelectric transition. Our results imply that improper ferroelectric ultrathin films can have rather unique properties that are distinctive from those of very thin films of ordinary ferroelectrics.The integration of ferroelectric oxide materials into existing microelectronic device architectures is currently of much interest as they hold promise for a wide range of potentially new applications [1,2]. This has generated an enormous effort to understand the properties of ferroelectric perovskite ultrathin films, such as BaTiO 3 , where it has been shown that electrical boundary conditions [3,4,5,6], surface and interface properties [7,8,9,10], as well as epitaxial strain [11,12] all play an important role. Although there appears to be no fundamental size limit below which ferroelectricity disappears, ultrathin ferroelectric films with the polarization normal to the surface remain a challenge. This is because the depolarization field arising from the accumulated charges at the surfaces, if not screened, can strongly suppress the instability towards a single-domain ferroelectric state. This is indeed what happens in a material displaying a proper ferroelectric transition (note, henceforth we refer to such materials as proper ferroelectrics), namely one where the primary order parameter is the electrical polarization, e.g., BaTiO 3 . The depolarizing field contributes to the free energy a positive term quadric in the polarization thereby re-normalizing the soft-mode energy and stabilizing the paraelectric phase. Even in a system with metallic electrodes, which can provide the necessary screening in most cases, when the thickness of the ferroelectric film becomes comparable to the effective screening length of the metal, the screening is incomplete resulting in a reduced polarization [5,7,13], an increased coercive field [14], and in some case suppress the tendency towards (single-domain) ferroelectricity completely.It would clearly be advantageous, if not at least fundamentally interesting, to consider the surface properties of ultrathin films of materials in which ferroelectricity did not originate from a polar instability, but rather from an improper ferroelectric transition -i.e., one where the spontaneous polarization does not drive the transition but instead is a slave to some other primary order parameter. As pointed out decades ago by Levanyuk and San- nikov in a series of papers [15,16], an instability towards a single-domain ferroelectric state in a improper ferroelectric is still possible even if the depolarization field remains unscreened, e.g., under ope...

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X-Ray investigations of the crystal structure and phase transitions of YMnO₃

Cited by 95 publications

References 1 publication

Elastic anomalies associated with structural and magnetic phase transitions in single crystal hexagonal YMnO₃

Elastic anomalies associated with structural and magnetic phase transitions in single crystal hexagonal YMnO₃

Combinatorial model for the ferroelectric domain-network formation in hexagonal manganites

Absence of Critical Thickness in an Ultrathin Improper Ferroelectric Film

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X-Ray investigations of the crystal structure and phase transitions of YMnO3

Cited by 95 publications

References 1 publication

Elastic anomalies associated with structural and magnetic phase transitions in single crystal hexagonal YMnO3

Elastic anomalies associated with structural and magnetic phase transitions in single crystal hexagonal YMnO3

Combinatorial model for the ferroelectric domain-network formation in hexagonal manganites

Absence of Critical Thickness in an Ultrathin Improper Ferroelectric Film

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Product

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X-Ray investigations of the crystal structure and phase transitions of YMnO₃

Elastic anomalies associated with structural and magnetic phase transitions in single crystal hexagonal YMnO₃

Elastic anomalies associated with structural and magnetic phase transitions in single crystal hexagonal YMnO₃