Three-Dimensional Pseudo-Ferroelectric Domain Walls in BiFeO<sub>3</sub>: Atomic-Scale Oxygen Octahedral Rotation and Polar Geometry.
basic_science · Level V
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- Record sourced from PubMed, PMID 42262885.
- Also identified by DOI 10.1021/acs.nanolett.6c02003.
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Abstract
The emergence of multiferroic order in perovskite thin films is governed by symmetry-broken coupling between polar domains and magnetic order parameters; however, currently prevailing theoretical frameworks, due to a constraint of reduced-dimensional approximations, fail to capture the inherent three-dimensional (3D) complexity of domain-mediated cross-correlations. Here, performing atomic-resolution HAADF/iDPC-STEM on BiFeO<sub>3</sub> (BFO), we discover a "pseudo-ferroelectric domain wall" bridging (1<math xmlns="http://www.w3.org/1998/Math/MathML"><mover><mi>1</mi><mo>¯</mo></mover><mover><mi>4</mi><mo>¯</mo></mover></math>)<sub>h</sub>/(<math xmlns="http://www.w3.org/1998/Math/MathML"><mover><mi>1</mi><mo>¯</mo></mover><mover><mi>1</mi><mo>¯</mo></mover></math>0)<sub>h</sub> planes of BFO, in which two-dimensional (2D) projection indicates a domain-wall angle of 54.37°, but the actual 3D orientation remains 70.17°. When the (1<math xmlns="http://www.w3.org/1998/Math/MathML"><mover><mi>1</mi><mo>¯</mo></mover><mover><mi>4</mi><mo>¯</mo></mover></math>)<sub>h</sub> plane is rotated 90° about the [2<math xmlns="http://www.w3.org/1998/Math/MathML"><mover><mi>2</mi><mo>¯</mo></mover><mn>1</mn></math>]<sub>h</sub> axis, it reveals the atomic arrangement of the (<math xmlns="http://www.w3.org/1998/Math/MathML"><mover><mi>1</mi><mo>¯</mo></mover><mover><mi>1</mi><mo>¯</mo></mover></math>0)<sub>h</sub> plane, with polarization along [00<math xmlns="http://www.w3.org/1998/Math/MathML"><mover><mi>1</mi><mo>¯</mo></mover></math>]. These noncanonical 3D walls arise from oxygen-rearrangement-induced structural deviations and asymmetric Fe-O lattice coupling, which generate chiral polarization stabilized by a potent tripartite interaction between ferroelectric, shear, and spin degrees of freedom. This work provides a design principle for reconfigurable domain wall nanoelectronics.