Atomic-scale engineering of ferroelectric-ferromagnetic interfaces of epitaxial perovskite films for functional properties

Hausmann, Simon; Ye, Jingfan; Aoki, Toshihiro; Zheng, Jian‐Guo; Stahn, Jochen; Bern, Francis; Chen, Binda; Autieri, Carmine; Sanyal, Biplab; Esquinazi, P.; Böni, P.; Paul, Amitesh

doi:10.1038/s41598-017-10194-4

Cited by 12 publications

(9 citation statements)

References 41 publications

(63 reference statements)

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“…Multilayered structures incorporating ferroelectric perovskites and metal/oxide electrodes have extensively been investigated for their use in a wide range of advanced applications, including but not limited to (multiple state) ferroelectric memories [1][2][3][4][5], quantum tunneling junctions [6][7][8][9][10][11][12][13][14], photo-ferroic solar cells [15][16][17][18][19][20][21][22][23][24], and various multilevel architectures with coupled ferroic modes [25][26][27][28][29][30][31][32][33][34]. Also, new experimental methods have been envisaged for acquiring an accurate control of polarization when the ferroelectric layer is situated deep into these structures [35][36][37][38].…”

Section: Introductionmentioning

confidence: 99%

Designing functional ferroelectric interfaces from first-principles: dipoles and band bending at oxide heterojunctions

et al. 2019

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The fundamental phenomena at ferroelectric interfaces have been the subject of thorough theoretical and computational studies due to their usefulness in a large variety of emergent electronic devices, solar cells and catalysts. Ferroelectricity determines interface band-bending and shifts in electron energies, which can be beneficial or detrimental to device performance. However, the underlying mechanisms are still the subject of debate and investigation, as a deeper understanding of the electrochemistry is required to develop bona fide design principles for functional ferroelectric surfaces and interfaces. Here, using first principles calculations within the GGA+U formalism, we investigate the problem of band alignment in non-defective, asymmetric SrRuO 3 /PbTiO 3 /SrRuO 3 capacitors with ultra-thin ferroelectric layers. The effects of the dielectric size on the polar distortion stability and interface-specific properties are analyzed. It is shown that the critical size of the dielectric for polarization switching is 2 nm » (5 PbTiO 3 u.c.). Below this limit there is no bulk-like region in the dielectric, the space charge accumulated at interfaces leads to the presence of gap states in the whole PbTiO 3 layer and ferroelectricity vanishes. We draw the band alignment diagrams as given by the band line-up and band structure terms, as well as by taking Ti 3s semi-core states as reference. In the ferroelectric structures, both approaches predict a strong effect of band-bending on the type of contact, Schottky or Ohmic, at the asymmetric interfaces. The effect of interface states on the interface dipole amplitude and band alignment is discussed.

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Section: Introductionmentioning

confidence: 99%

Designing functional ferroelectric interfaces from first-principles: dipoles and band bending at oxide heterojunctions

et al. 2019

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“…To optimize such structures, the control of interfaces will be critical and could rely on the accumulated knowledge acquired through the study of multiferroic heterostructures. Here, ionic, electronic, strain and exchange couplings at interfaces result in transition regions, often down to a couple of atomic layers only, both in the ferroelectric and ferromagnetic materials [167][168][169][170][171][172][173][174] . Symmetry breakings have also been observed in homogeneous thick films 175,176 .…”

Section: Transition Regionsmentioning

confidence: 99%

Domain-wall engineering and topological defects in ferroelectric and ferroelastic materials

et al. 2020

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Ferroelectric and ferroelastic domain walls are two-dimensional (2D) topological defects with thicknesses approaching the unit cell level. When this spatial confinement is combined with observations of emergent functional properties, such as polarity in non-polar systems or electrical conductivity in otherwise insulating materials, it becomes clear that domain walls represent a new and exciting state of matter. In this review, we discuss the exotic polarisation profiles that can arise at domain walls with multiple order parameters and the different mechanisms that lead to domain wall polarity in non-polar ferroelastic materials. The emergence of energetically degenerate variants of the domain walls themselves suggests the existence of interesting quasi-1D topological defects within such walls. We also provide an overview of the general notions which have been postulated as fundamental mechanisms responsible for domain wall conduction in ferroelectrics. We then discuss the prospect of combining domain walls with transition regions observed at phase boundaries, homo-and heterointerfaces, and other quasi-2D objects, enabling emergent properties beyond those available in today's topological systems. Key points• In ferroelectrics, the emergence of a second polarisation component leads to analogues of Bloch and Néel walls. The stabilization of these walls opens the possibility for quasi-1D topological defects separating wall regions of opposite polarities.• Polar domain walls in ferroelastics rely on two mechanisms: a polarity imposed by the natural symmetry of strain-compatible domain walls, which can often be described by flexoelectric gradient coupling, and the emergence of a potentially switchable polarity when their natural symmetry is broken.• Several mechanisms are responsible for domain wall conduction in ferroelectrics: extrinsic intra-bandgap defect states, intrinsic suppression of the conduction band and intrinsic shift of the band structure induced by local electric fields.• Transition regions occurring at phase boundaries, homo-and heterointerfaces, and other quasi-2D objects probably exist at a smaller length scale, in the vicinity of domain walls, and could lead to exceptional properties and coupling phenomena.

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“…The χ 2 value for model 1 is slightly better than model 2 and worsens for model 3. Thus, we cannot ascertain a complete dead layer formation 30 . A reduced magnetic moment value at the interface seems to be more plausible here.…”

Section: Resultsmentioning

confidence: 97%

Proximity effects across oxide-interfaces of superconductor-insulator-ferromagnet hybrid heterostructure

Prajapat

Singh

Bhattacharya

et al. 2018

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A case study of electron tunneling or charge-transfer-driven orbital ordering in superconductor (SC)-ferromagnet (FM) interfaces has been conducted in heteroepitaxial YBa2Cu3O7(YBCO)/La0.67Sr0.33MnO3(LSMO) multilayers interleaved with and without an insulating SrTiO3(STO) layer between YBCO and LSMO. X-ray magnetic circular dichroism experiments revealed anti-parallel alignment of Mn magnetic moments and induced Cu magnetic moments in a YBCO/LSMO multilayer. As compared to an isolated LSMO layer, the YBCO/LSMO multilayer displayed a (50%) weaker Mn magnetic signal, which is related to the usual proximity effect. It was a surprise that a similar proximity effect was also observed in a YBCO/STO/LSMO multilayer, however, the Mn signal was reduced by 20%. This reduced magnetic moment of Mn was further verified by depth sensitive polarized neutron reflectivity. Electron energy loss spectroscopy experiment showed the evidence of Ti magnetic polarization at the interfaces of the YBCO/STO/LSMO multilayer. This crossover magnetization is due to a transfer of interface electrons that migrate from Ti(4+)−δ to Mn at the STO/LSMO interface and to Cu2+ at the STO/YBCO interface, with hybridization via O 2p orbitals. So charge-transfer driven orbital ordering is the mechanism responsible for the observed proximity effect and Mn-Cu anti-parallel coupling in YBCO/STO/LSMO. This work provides an effective pathway in understanding the aspect of long range proximity effect and consequent orbital degeneracy parameter in magnetic coupling.

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Atomic-scale engineering of ferroelectric-ferromagnetic interfaces of epitaxial perovskite films for functional properties

Cited by 12 publications

References 41 publications

Designing functional ferroelectric interfaces from first-principles: dipoles and band bending at oxide heterojunctions

Designing functional ferroelectric interfaces from first-principles: dipoles and band bending at oxide heterojunctions

Domain-wall engineering and topological defects in ferroelectric and ferroelastic materials

Proximity effects across oxide-interfaces of superconductor-insulator-ferromagnet hybrid heterostructure

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