Oxygen-vacancy induced magnetic phase transitions in multiferroic thin films

César Menéndez,Claudio Cazorla,Dewei Chu

doi:10.1038/s41524-020-0344-3

César Menéndez, Claudio Cazorla + Show 1 more

Open Access

https://doi.org/10.1038/s41524-020-0344-3

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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 the high temperatures involved in the synthesis of materials. 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 considerable net magnetizations. 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.

Highlights

Finding multiferroics in which ferroelectricity and magnetism coexist and influence each other is of great fundamental and applied interests[1,2]
Multiferroics are rare in nature, typically present weak magnetoelectric coupling (BiFeO3)[11], and require extreme thermodynamic conditions for their synthesis (PbVO3 and BiCoO3)[12,13,14]
We have performed first-principles simulations of stoichiometric and non-stoichiometric BCO thin films based on density functional theory (DFT) techniques

Summary

Introduction

Finding multiferroics in which ferroelectricity and magnetism coexist and influence each other is of great fundamental and applied interests[1,2]. Salient technological features of multiferroics include the control of the magnetization with electric fields to design efficient logic and memory devices[3,4], and the realization of large piezomagnetic coefficients to facilitate the miniaturization of antennas and sensors[5,6]. Magnetoelectric multiferroics mostly are antiferromagnetic potential applications based on external magnetic bias generally are frustrated due to their little influence on antiparallel magnetic spins[15]. Common strategies employed to synthesize bettered multiferroic materials include doping[16,17], solid solutions[18,19], and strain engineering[1,20]

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