# Engineering Unequal Antipolar Displacement in Ferromagnetic Layered Oxide Heterostructures

## TL;DR

Researchers engineered a new type of oxide superlattice with unique structural and magnetic properties that could lead to hybrid improper ferroelectricity.

## Contribution

The study demonstrates unequal antipolar displacements in ferromagnetic oxide superlattices, enabling new functional properties.

## Key findings

- Unequal antipolar displacements of La and Sm ions were confirmed using electron microscopy and calculations.
- The superlattices exhibit robust ferromagnetism and structural motifs that could enable hybrid improper ferroelectricity.

## Abstract

Heterostructure engineering provides a versatile route for tailoring emergent functionalities that are often difficult to realize in single‐phase materials. In this work, the focus is on superlattices composed of the insulating and ferromagnetic double perovskites La2NiMnO6 and Sm2NiMnO6, which constitute an intriguing model system. These layered structures are predicted to feature unequal antipolar displacements of the La and Sm ions; when combined with odd periodicity stacking, this structural motif is expected to give rise to polar behavior. The respective superlattices are grown with atomic precision and display robust ferromagnetism, as confirmed by in‐house magnetometry and synchrotron measurements. Scanning transmission electron microscopy combined with first‐principles calculations confirms the presence of the predicted unequal antipolar displacements, paving the way for the realization of hybrid improper ferroelectricity in such oxide heterostructures.

Atomically precise superlattices of the double perovskites La2NiMnO6 and Sm2NiMnO6 are grown to engineer an unequal antipolar displacement of the La and Sm ions. These structural motifs are confirmed by the scanning transmission electron microscopy and first‐principles calculations. Combined with their robust ferromagnetism, these heterostructures demonstrate a promising pathway toward hybrid improper ferroelectricity in artificially layered oxide systems.