Inducing and Manipulating Magnetization in Two-Dimensional ZnO by Strain and External Gating

TL;DR

This study uses density-functional theory to show how strain and external gating can induce and reverse magnetization in vacancy-doped 2D ZnO, enabling control of magnetic properties for spintronics.

Contribution

It reveals that strain and electric fields can switch the magnetization direction in ZnO monolayers with vacancies, a novel approach for magnetic manipulation in 2D materials.

Findings

Zn-vacancies induce significant magnetic moments in ZnO monolayers.

Magnetization easy axis can be reversed from in-plane to perpendicular with ~1-2% biaxial strain.

Electric-field application can also switch magnetization direction via charge density modulation.

Abstract

Two-dimensional structures that exhibit intriguing magnetic phenomena such as perpendicular magnetic anisotropy and switchable magnetization are of great interests in spintronics research. Herein, the density-functional theory studies reveal the critical impacts of strain and external gating on vacancy-induced magnetism and its spin direction in a graphene-like single layer of zinc oxide (ZnO). In contrast to the pristine and defective ZnO with an O-vacancy, the presence of a Zn-vacancy induces significant magnetic moments to its first neighboring O and Zn atoms due to the charge deficit. We further predict that the direction of magnetization easy axis reverses from an in-plane to perpendicular orientation under a practically achieved biaxial compressive strain of $\sim$1--2\% or applying an electric-field by means of the charge density modulation. This magnetization reversal is driven by the strain- and electric-field-induced changes in the spin-orbit coupled \emph{d} states of the first-neighbor Zn atom to the Zn-vacancy. These findings open interesting prospects for exploiting strain and electric-field engineering to manipulate magnetism and magnetization orientation of two-dimensional materials.