Suppression of vortex–antivortex structures by anti-trimer point defects in hexagonal manganites

Abstract

The topologically protected vortex–antivortex (V–AV) domain structure in ferroelectric hexagonal manganites has been highly concerned recently, but its stability against intrinsic defects remains to be understood, given the claim that a topological structure would be robust against defects and other perturbations. In fact, it is also known that the V–AV structure is sensitive to the sample quality, and such a well-developed structure is hardly observed in thin films and defective single crystals. In this work, we investigate the influence of anti-trimer point defects on the stability of the V–AV domain structure by employing the phase-field simulation based on the Landau–Devonshire phenomenological theory. It is revealed that the characteristic V–AV structure essentially relies on the anti-trimer point defects under consideration. These defects lower the trimerization transition temperature on one hand and produce pinning effect on the vortex cores/walls on the other hand. However, the V–AV structure does remain robust if the anti-trimer magnitude of these defects is relatively weak but will be eventually destroyed if the anti-trimer magnitude is strong.

Critical Role of Sc Substitution in Modulating Ferroelectricity in Multiferroic LuFeO3

“…Such effects could be investigated further using, e.g., large-scale DFT calculations 33 or phenomenological modeling. 46 Nevertheless, our theoretical assessment further underlines the key roles that Sc atoms play in determining improper ferroelectricity of the h-Lu 1−x Sc x FeO 3 system by small perturbations of the local atomic and electronic structure, consistent with experimental results. On this base, the strong dependence of improper ferroelectricity on Sc substitutional atoms is readily established regarding both their distribution and concentration.…”

“…This could lead to local fluctuations in T C , with the corresponding heterogeneous formation of the ferroelectric state when cooling across T C , which, in turn, could affect the resulting local R -cation displacements. Such effects could be investigated further using, e.g., large-scale DFT calculations or phenomenological modeling . Nevertheless, our theoretical assessment further underlines the key roles that Sc atoms play in determining improper ferroelectricity of the h -Lu 1– x Sc x FeO 3 system by small perturbations of the local atomic and electronic structure, consistent with experimental results.…”

First-principles study of topologically protected vortices and ferroelectric domain walls in hexagonal YGaO3

“…An alternate strategy to model different domain wall profiles is to use a phase field approach [69] combined with Ginzburg-Landau-Devonshire potentials parameterized using DFT [70,71]. Such phenomenological modeling approaches have been demonstrated to successfully describe charged domain walls in YGaO 3 [41], as well as topological defects in the hexagonal manganites [37,72]. While we see clear similarities between our results from large-scale DFT calculations using CONQUEST and results from phenomenological modeling, we note, however, that phenomenological modeling approaches cannot capture some of the subtle local perturbations on the atomic scale, such as the asymmetric domain wall crystal structure with respect to Y termination [41], that we can extract from our large-scale atomistic DFT simulations.…”