Giant magnetoelectric effect at the graphone/ferroelectric interface

Jie Wang,Yajun Zhang,M P K Sahoo,Takayuki Kitamura,Tong-Yi Zhang,Philippe Ghosez,Takahiro Shimada

doi:10.1038/s41598-018-30010-x

Abstract

Multiferroic heterostructures combining ferromagnetic and ferroelectric layers are promising for applications in novel spintronic devices, such as memories with electrical writing and magnetic reading, assuming their magnetoelectric coupling (MEC) is strong enough. For conventional magnetic metal/ferroelectric heterostructures, however, the change of interfacial magnetic moment upon reversal of the electric polarization is often very weak. Here, by using first principles calculations, we demonstrate a new pathway towards a strong MEC at the interface between the semi-hydrogenated graphene (also called graphone) and ferroelectric PbTiO3. By reversing the polarization of PbTiO3, the magnetization of graphone can be electrically switched on and off through the change of carbon-oxygen bonding at the interface. Furthermore, a ferroelectric polarization can be preserved down to ultrathin PbTiO3 layers less than one nanometer due to an enhancement of the polarization at the interface. The predicted strong magnetoelectric effect in the ultimately thin graphone/ferroelectric layers opens a new opportunity for the electric control of magnetism in high-density devices.

Highlights

The coupling of ferromagnetic and ferroelectric orders in multiferroic materials has attracted continuous attention due to its potential use in novel spintronic devices such as data-storage devices for writing electrically and reading magnetically[1,2,3,4,5]
The in-plane sizes of the supercell are constrained at 7.81 Å and 3.905 Å in [100] and [010] directions to simulate the growth on SrTiO3 substrate. Such a substrate produces an epitaxial strain on PTO and forces a ferroelectric tetragonal phase with polarization perpendicular to the interface[54] as generally used to control magnetism at the interface in multiferroic heterostructures
We demonstrate that the magnetization emerging in the graphone layer exhibits strong sensitivity to the direction of the ferroelectric polarization, and can even be electrically switched on and off by reversing the polarization, yielding a novel non-magnetic-ferromagnetic (NM-FM) phase transition

Summary

Introduction

The coupling of ferromagnetic and ferroelectric orders in multiferroic materials has attracted continuous attention due to its potential use in novel spintronic devices such as data-storage devices for writing electrically and reading magnetically[1,2,3,4,5]. Composite multiferroics made of ferroelectric and ferromagnetic constituents are abundant in the form of heterostructures, in which MEC exists at the interface through different mechanisms[7,8,9,10,11,12]. One kind of such heterostructures investigated so far consist in multilayers combining a conventional ferromagnetic metal and a ferroelectric insulator perovskite oxide. The electronic and magnetic properties of the interface between graphene and ME multiferroics were investigated by using first principles calculations[46], yet the screening effect of graphene or graphone on the polarization in ultrathin ferroelectric films is unclear so far. Whether there exists an interfacial MEC between the graphone and ferroelectric perovskite oxide is unknown

Methods

Results

Conclusion