Unusual nanoscale coexistence of polar-nonpolar domains underlying oxygen storage properties in Ho(Mn, Ti)O$_{3+\delta}$

TL;DR

This study uncovers the coexistence of polar and nonpolar nanoscale domains in Ho(Mn, Ti)O$_{3+}$, revealing their impact on oxygen storage properties and advancing understanding of domain engineering in manganese oxides.

Contribution

It demonstrates the formation of polar-nonpolar nanoscale domains via Ti substitution in HoMnO$_3$, linking microstructural changes to oxygen storage capabilities.

Findings

Unprecedented coexistence of polar and nonpolar domains observed.

Reversible microstructural transition correlates with oxygen storage.

Nanoscale domain structure influences functional properties.

Abstract

Hexagonal manganese oxides RMnO$_3$ show intriguing topological ferroelectric-domain walls with variable conductivity, leading to domain wall engineering. Despite the numerous experimental studies on the polar nanoscale structures, controlling ferroelectric domains has not been sufficiently investigated. Here, we reveal the unprecedented coexistence of polar-nonpolar nanoscale domains that can be formed by substituting Ti ions in HoMnO$_3$. Unusual polar nanoscale domains are embedded in nonpolar domains with different crystallographic symmetry. This polar-nonpolar coexisting structure is naturally assembled by adjusting the lattice length during a solid-state reaction process. Furthermore, the comprehensive study reveals that the reversible microstructural change with a nonpolar-polar transition is strongly correlated with the oxygen storage properties in Ho(Mn, Ti)O$_{3+\delta}$. The present results provide important insight into the nanoscale polar-nonpolar domain coexistence in functional rare-earth manganese oxides, RMnO$_3$.