Evidence for Room-Temperature Multiferroicity in a Compound with a Giant Axial Ratio

Béa, Hélène; Dupé, Bertrand; Fusil, S.; Mattana, R.; Jacquet, Éric; Warot-Fonrose, Bénédicte; Wilhelm, F.; Рогалев, А.; Petit, S.; Cros, Vincent; Anane, A.; Pétroff, F.; Bouzéhouane, K.; Geneste, G.; Dkhil, Brahim; Lisenkov, S.; Ponomareva, I.; Bellaïche, L.; Bibès, Manuel; Barthélémy, A.

doi:10.1103/physrevlett.102.217603

Cited by 343 publications

(265 citation statements)

References 38 publications

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“…The lone pair (s 2 orbital) on the Bi cation plays an important role in driving the spontaneous polarization4 that varies between ≈1 C m −2 for the rhombohedral5 phase to a predicted 1.50 C m −2 for the strain‐stabilized pseudotetragonal phase,6 one of the highest among perovskite structures. Experimentally, it has been shown that strain can be used to induce a morphotropic phase transition in BiFeO 3 thin films7, 8, 9, 10, 11 with a structural transformation from the rhombohedral phase to a monoclinic pseudotetragonal ( T ′) phase at compressive epitaxial strains exceeding ≈4.5%. Most strikingly, the T ′ phase is not structurally uniform but rather a mixed phase exhibiting stripe patterns with a larger piezoresponse than the pure R and T ′ phases, which is believed to be a consequence of the phase interconversion in an applied electric field 12…”

Section: Introductionmentioning

confidence: 99%

Understanding Strain‐Induced Phase Transformations in BiFeO₃ Thin Films

et al. 2015

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Experiments demonstrate that under large epitaxial strain a coexisting striped phase emerges in BiFeO3 thin films, which comprises a tetragonal‐like (T′) and an intermediate S′ polymorph. It exhibits a relatively large piezoelectric response when switching between the coexisting phase and a uniform T′ phase. This strain‐induced phase transformation is investigated through a synergistic combination of first‐principles theory and experiments. The results show that the S′ phase is energetically very close to the T′ phase, but is structurally similar to the bulk rhombohedral (R) phase. By fully characterizing the intermediate S′ polymorph, it is demonstrated that the flat energy landscape resulting in the absence of an energy barrier between the T′ and S′ phases fosters the above‐mentioned reversible phase transformation. This ability to readily transform between the S′ and T′ polymorphs, which have very different octahedral rotation patterns and c/a ratios, is crucial to the enhanced piezoelectricity in strained BiFeO3 films. Additionally, a blueshift in the band gap when moving from R to S′ to T′ is observed. These results emphasize the importance of strain engineering for tuning electromechanical responses or, creating unique energy harvesting photonic structures, in oxide thin film architectures.

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Section: Introductionmentioning

confidence: 99%

Understanding Strain‐Induced Phase Transformations in BiFeO₃ Thin Films

et al. 2015

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“…The measured c/a ratio for Ca1-xCexMnO3 is of the order of 1.02±0.03. In the vicinity to the Ca1-xCexMnO3/BiFeO3 interfaces the c/a ratio of the last Ca1-xCexMnO3 unit cells slightly increases and in the BiFeO3 it reaches within 3 unit cells the c/a ratio ≥1.25±0.03 which is indicative of the highly tetragonal BiFeO3 phase 19 . The stabilization of this highly tetragonal BiFeO3 phase (with ferroelectric polarization >100 µC/cm 2 ) is induced by the in-plane compressive strain of the YAlO3 substrates 20 .…”

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Depth Profiling Charge Accumulation from a Ferroelectric into a Doped Mott Insulator

et al. 2015

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The electric field control of functional properties is a crucial goal in oxide-based electronics.Non-volatile switching between different resistivity or magnetic states in an oxide channel can be achieved through charge accumulation or depletion from an adjacent ferroelectric. However, the way in which charge distributes near the interface between the ferroelectric and the oxide remains poorly known, which limits our understanding of such switching effects.Here we use a first-of-a-kind combination of scanning transmission electron microscopy with electron energy loss spectroscopy, near-total-reflection hard X-ray photoemission spectroscopy, and ab-initio theory to address this issue. We achieve a direct, quantitative, atomic-scale characterization of the polarization-induced charge density changes at the interface between the ferroelectric BiFeO3 and the doped Mott insulator Ca1-xCexMnO3, thus providing insight on how interface-engineering can enhance these switching effects. 3The ferroelectric control of functional properties in strongly correlated oxide nanostructures through electrostatic carrier density modulations has inspired intensive research efforts 1,2 .The field effect technique is particularly attractive for nanostructures consisting of complex oxides such as mixed-valence manganites, as these electron-correlated systems exhibit rich phase diagrams 3 .Hole-doped mixed-valence manganites with predominant Mn 3+ oxidation state have been extensively investigated [3][4][5][6][7][8] . In particular, recent works have been devoted on the interface between the half-metal La1-xSrxMnO3 (LSMO) manganite and ferroelectrics such as Pb(ZrxTi1- In these recent reports 13,14 , the resistivity change in the manganite channel induced by polarization switching in the ferroelectric BiFeO3 was limited to one order of magnitude while changes of several orders were reported for thin films of CaMnO3 tuned by different doping levels, strains or by electrolyte gating 12 . Typical electron injection of around 0.1 free electrons in the manganite channel were estimated by Hall measurements and associated with this resistivity change.A charge distribution measurement on a unit cell scale at the Ca manganite/ferroelectric interface is thus required to understand, control and possibly enhance the magnitude of the resistivity switching effects. In the present study, a first-of-a-kind combination of scanning transmission electron microscopy (STEM) coupled to electron energy loss spectroscopy (EELS) [15][16][17][18] , and grazing-incidence hard x-ray photoemission spectroscopy (HAXPES) in a near-total-reflection (NTR) condition have been used as site-sensitive valence probes to address the electronic and structural properties of BiFeO3 and Ca1-xCexMnO3 heterostructures (x=0, 2, 4 at.% nominal Ce concentrations) at the atomic scale. Our experimental results have also been compared to local density functional theory (DFT).We have used these two novel and complementary methods to evaluate electron densities in manganite oxides. ...

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“…[17] Other thin film studies, however, have shown that 3 a tetragonally-distorted phase (derived from a structure with P4mm symmetry, a ~ 3.665 Å, and c ~ 4.655 Å) with a large spontaneous polarization may be possible. [15,18,19] Furthermore, so-called mixed-phase thin-films possessing tetragonal-and rhombohedral-like phases in complex stripe-like structures that give rise to enhanced electromechanical responses were also reported. [7] Since this report, additional information has come forth about these materials including the fact that the tetragonal-like phase is actually monoclinically distorted (possessing Cc, Cm, Pm, or Pc symmetry).…”

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Nanoscale Structure and Mechanism for Enhanced Electromechanical Response of Highly Strained BiFeO₃ Thin Films

et al. 2011

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The nanostructural evolution of the strain-induced structural phase transition in BiFeO 3 is examined. Using high-resolution X-ray diffraction and scanning-probe microscopy-based studies we have uniquely identified and examined the numerous phases present at these phase boundaries and have discovered an intermediate monoclinic phase in addition to the previously observed rhombohedral-and tetragonallike phases. Further analysis has determined that the so-called mixed-phase regions of these films are not mixtures of rhombohedral-and tetragonal-like phases, but intimate mixtures of highly-distorted monoclinic phases with no evidence for the presence of the rhombohedral-like parent phase. Finally, we propose a mechanism for the enhanced electromechanical response in these films including how these phases interact at the nanoscale to produce large surface strains.

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Evidence for Room-Temperature Multiferroicity in a Compound with a Giant Axial Ratio

Cited by 343 publications

References 38 publications

Understanding Strain‐Induced Phase Transformations in BiFeO₃ Thin Films

Understanding Strain‐Induced Phase Transformations in BiFeO₃ Thin Films

Depth Profiling Charge Accumulation from a Ferroelectric into a Doped Mott Insulator

Nanoscale Structure and Mechanism for Enhanced Electromechanical Response of Highly Strained BiFeO₃ Thin Films

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Evidence for Room-Temperature Multiferroicity in a Compound with a Giant Axial Ratio

Cited by 343 publications

References 38 publications

Understanding Strain‐Induced Phase Transformations in BiFeO3 Thin Films

Understanding Strain‐Induced Phase Transformations in BiFeO3 Thin Films

Depth Profiling Charge Accumulation from a Ferroelectric into a Doped Mott Insulator

Nanoscale Structure and Mechanism for Enhanced Electromechanical Response of Highly Strained BiFeO3 Thin Films

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Understanding Strain‐Induced Phase Transformations in BiFeO₃ Thin Films

Understanding Strain‐Induced Phase Transformations in BiFeO₃ Thin Films

Nanoscale Structure and Mechanism for Enhanced Electromechanical Response of Highly Strained BiFeO₃ Thin Films