# Oxygen-vacancy induced magnetic phase transitions in multiferroic thin films

## TL;DR

This paper demonstrates through theoretical methods that oxygen vacancies can enhance multiferroic thin films by inducing magnetic phase transitions, restoring magnetic interactions, and stabilizing ferrimagnetic states, thus improving their functional properties.

## Contribution

It reveals how oxygen vacancies can be used to control magnetic phases in multiferroic thin films, providing insights for better material design.

## Key findings

- Oxygen vacancies restore magnetic super-exchange interactions.
- Induction of full antiferromagnetic spin ordering.
- Stabilization of ferrimagnetic states with net magnetization.

## Abstract

Multiferroics in which giant ferroelectric polarization and magnetism coexist are of tremendous potential for engineering disruptive applications in information storage and energy conversion. Yet the functional properties of multiferroics are thought to be affected detrimentally by the presence of point defects, which may be abundant due to the volatile nature of some constituent atoms and high temperatures involved in materials preparation. Here, we demonstrate with theoretical methods that oxygen vacancies may enhance the functionality of multiferroics by radically changing their magnetic interactions in thin films. Specifically, oxygen vacancies may restore missing magnetic super-exchange interactions in large axial ratio phases, leading to full antiferromagnetic spin ordering, and induce the stabilization of ferrimagnetic states with a significant net magnetization of 0.5 uB per formula unit. Our theoretical study should help to clarify the origins of long-standing controversies in bismuth ferrite and improve the design of technological applications based on multiferroics.