Charged domain walls in improper ferroelectric hexagonal manganites and gallates

TL;DR

This study investigates the structure and energetics of charged domain walls in improper ferroelectric materials YMnO₃, InMnO₃, and YGaO₃, revealing how to engineer their conductivity for nanoelectronic applications.

Contribution

The paper provides first-principles and phenomenological insights into charged domain walls in improper ferroelectrics, offering rules for tuning their electronic properties for device design.

Findings

Charged walls are asymmetric in structure and width.

Wall width scales with structural order parameter and coupling strength.

Guidelines for engineering domain wall conductivity and p-n junctions.

Abstract

Ferroelectric domain walls are attracting broad attention as atomic-scale switches, diodes and mobile wires for next-generation nanoelectronics. Charged domain walls in improper ferroelectrics are particularly interesting as they offer multifunctional properties and an inherent stability not found in proper ferroelectrics. Here we study the energetics and structure of charged walls in improper ferroelectric YMnO$_3$, InMnO$_3$ and YGaO$_3$ by first principles calculations and phenomenological modeling. Positively and negatively charged walls are asymmetric in terms of local structure and width, reflecting that polarization is not the driving force for domain formation. The wall width scales with the amplitude of the primary structural order parameter and the coupling strength to the polarization. We introduce general rules for how to engineer $n$- and $p$-type domain wall conductivity based on the domain size, polarization and electronic band gap. This opens the possibility of fine-tuning the local transport properties and design $p$-$n$-junctions for domain wall-based nano-circuitry.