Direct observation of interlocked domain walls in hexagonalRMnO3(R=Tm, Lu)

Abstract

Using state-of-the-art aberration-corrected annular-bright-field and high-angle annular-dark-field scanning transmission electron microscopy, we investigated domain wall structures in multiferroic hexagonal TmMnO 3 and LuMnO 3 ceramics at the atomic scale. Two types of 180• domain walls (DWs), i.e., the transverse and the longitudinal DWs with uniform displacements of a/3 and 2a/3, respectively, were identified along the b direction, which is in agreement with the interlock between the ferroelectric and structural translation domain walls that had been predicted previously. Across the domain wall the arrangement of MnO 5 polyhedra was not found to be inversed, indicating that (i) it has negligible effects on the polarization and (ii) the structures of the neighbor domains with opposite polarizations are not exactly the same. These wall structures are different from the polarization inversion in conventional ferroelectrics and may be used to explain the unusual transport properties and magnetoelectic effects.

Scaling Behavior and Beyond Equilibrium in the Hexagonal Manganites

“…This finding sets an upper limit on 0 of the interatomic spacing of approximately 1 # A. While unusually narrow for a ferroelectric domain wall, such abrupt walls are not atypical for antiphase boundaries, and indeed our calculated value is consistent with a recent experimental electron-microscopy study at room temperature [36], indicating that our calculated zero-kelvin value is relevant over a wide temperature range. As an additional check, we have repeated our calculations for walls between domains of different trimerization phase and the same ferroelectric orientation, as well as between domains of opposite polarity but the same phase, and in all cases have obtained abrupt boundaries [37].…”

Homotopy-Theoretic Study & Atomic-Scale Observation of Vortex Domains in Hexagonal Manganites

“…When the proportion is 50%, the ambiguous contrast becomes most significant, and its intensity center approaches the middle plane of two Mn layers. So this may lead to the erroneous interpretation that there is an extra atomic column at the high-temperature mirror plane27. Moreover, “overlapping effect” also occurs in vortex core region.…”

“…Because of its substantial effect on local physical properties, the domain wall microstructure has been extensively studied via atomic-resolved transmission electron microscopy (TEM) and first-principles calculation. Indeed, the observed structural properties are quite interesting, and there is ongoing debate about the best structural model for the domain walls, and for the vortex core as well272829303132.…”

Delicate balance between ferroelectricity and antiferroelectricity in hexagonal InMnO3

“…The existence of such nanoscale PUA islands, which appear corresponding to speckles in DF-TEM images [ Fig. 2(b)], is certainly different from the behaviour of the thin domain walls with down-no-up distortions, which were, first, proposed as a possible configuration for the ferroelectrictrimerization domain walls in hexagonal YMnO 3 1 , studied theoretically 16 , and also observed experimentally 17 . We emphasize that in IMO-b, the PUA islands are very common, but the dominant phase is still the FE matrix.…”