Highly tunable ferroelectricity in hybrid improper ferroelectric Sr3Sn2O7

TL;DR

This paper reports the discovery and characterization of Sr3Sn2O7 as a highly tunable hybrid improper ferroelectric with the smallest coercive field among known HIFs, demonstrating potential for technological applications.

Contribution

It provides the first experimental realization of Sr3Sn2O7 as a HIF with low coercive field and demonstrates its switchability and domain behavior, supported by first-principles calculations.

Findings

Sr3Sn2O7 exhibits the smallest electric coercive field among HIFs.

External stress can erase and re-generate ferroelastic domains.

Low energy barriers for polarization switching are confirmed by calculations.

Abstract

The successful theoretical prediction and experimental demonstration of hybrid improper ferroelectricity (HIF) provides a new pathway to couple octahedral rotations, ferroelectricity, and magnetism in complex materials. To enable technological applications, a HIF with a small coercive field is desirable. We successfully grow Sr3Sn2O7 single crystals, and discover that they exhibit the smallest electric coercive field at room temperature among all known HIFs. Furthermore, we demonstate that a small external stress can repeatedly erase and re-generate ferroelastic domains. In addition, using in-plane piezo-response force microscopy, we characterize abundant charged and neutral domain walls. The observed small electrical and mechanical coercive field values are in accordance with the results of our first-principles calculations on Sr3Sn2O7, which show low energy barriers for both 90{\deg} and 180{\deg} polarization switching compared to those in other experimentally demonstrated HIFs. Our findings represent an advance towards the possible technological implemetation of functional HIFs.