Hybrid improper antiferroelectricity—New insights for novel device concepts

Antiferroelectrics have been studied for decades, with most research focused on PbZrO₃ or related compounds obtained through chemical substitution. Although there are several important antiferroelectrics found in AVO₄ (A=Dy, Bi), orthorhombic ABC semiconductors (e.g., MgSrSi) and hydrogen-bonded antiferroelectric materials, experimentally demonstrated antiferroelectrics are far less common. Furthermore, antiferroelectrics have potential applications in energy storage and for strain and force generators. In recent years, hybrid improper ferroelectrics have been intensively studied, along which the hybrid improper antiferroelectric phase was proposed and demonstrated in (001) Ruddlesden-Popper A₃B₂O₇ thin films from first-principles calculations. Later, the hybrid improper antiferroelectric phase was discovered experimentally in several Ruddlesden-Popper perovskites in bulk. Across the hybrid improper ferroelectric-antiferroelectric phase transition, several interesting phenomena were also predicted. In this snapshot review, we describe recent progress in hybrid improper antiferroelectricity.