Reversal of the Magnetoelectric Effect at a Ferromagnetic Metal/Ferroelectric HfO₂ Interface Induced by Metal Oxidation

Authors

Zhaojin Chen, Xiangtan University
Qiong Yang, Xiangtan UniversityFollow
Lingling Tao, University of Nebraska-LincolnFollow
Evgeny Y. Tsymbal, University of Nebraska-LincolnFollow

ORCID IDs

Yang http://orcid.org/0000-0002-3235-1986

Tao http://orcid.org/0000-0001-6003-100X

Tsymbal http://orcid.org/0000-0002-6728-5480

Document Type

Article

Date of this Version

2021

Citation

npj Computational Materials (2021) 7: 204

doi: 10.1038/s41524-021-00679-2

Supplemental materials are available at https://doi.org/10.1038/s41524-021-00679-2

Comments

Copyright 2021, the authors. Open access

License: CC BY 4.0 International

Published in partnership with the Shanghai Institute of Ceramics of the Chinese Academy of Sciences

Abstract

Multiferroic materials composed of ferromagnetic and ferroelectric components are interesting for technological applications due to sizable magnetoelectric coupling allowing the control of magnetic properties by electric fields. Due to being compatible with the silicon-based technology, HfO₂-based ferroelectrics could serve as a promising component in the composite multiferroics. Recently, a strong charge-mediated magnetoelectric coupling has been predicted for a Ni/HfO₂ multiferroic heterostructure. Here, using density functional theory calculations, we systematically study the effects of the interfacial oxygen stoichiometry relevant to experiments on the magnetoelectric effect at the Ni/HfO₂ interface. We demonstrate that the magnetoelectric effect is very sensitive to the interface stoichiometry and is reversed if an oxidized Ni monolayer is formed at the interface. The reversal of the magnetoelectric effect is driven by a strong Ni−O bonding producing exchange-split polarization-sensitive antibonding states at the Fermi energy. We argue that the predicted reversal of the magnetoelectric effect is typical for other 3d ferromagnetic metals, such as Co and Fe, where the metal-oxide antibonding states have an opposite spin polarization compared to that in the pristine ferromagnetic metals. Our results provide an important insight into the mechanism of the interfacial magnetoelectric coupling, which is essential for the physics and application of multiferroic heterostructures.