Oxygen-enabled control of Dzyaloshinskii-Moriya Interaction in ultra-thin magnetic films.

Abderrezak Belabbes,Stefan Blügel,Gustav Bihlmayer,Aurélien Manchon

doi:10.1038/srep24634

Abstract

The search for chiral magnetic textures in systems lacking spatial inversion symmetry has attracted a massive amount of interest in the recent years with the real space observation of novel exotic magnetic phases such as skyrmions lattices, but also domain walls and spin spirals with a defined chirality. The electrical control of these textures offers thrilling perspectives in terms of fast and robust ultrahigh density data manipulation. A powerful ingredient commonly used to stabilize chiral magnetic states is the so-called Dzyaloshinskii-Moriya interaction (DMI) arising from spin-orbit coupling in inversion asymmetric magnets. Such a large antisymmetric exchange has been obtained at interfaces between heavy metals and transition metal ferromagnets, resulting in spin spirals and nanoskyrmion lattices. Here, using relativistic first-principles calculations, we demonstrate that the magnitude and sign of DMI can be entirely controlled by tuning the oxygen coverage of the magnetic film, therefore enabling the smart design of chiral magnetism in ultra-thin films. We anticipate that these results extend to other electronegative ions and suggest the possibility of electrical tuning of exotic magnetic phases.

Highlights

Systems with broken spatial inversion symmetry present a fascinating playground for the design of thought-intriguing ferroic behaviors[1] and the emergence of unexpected transport phenomena[2]
We propose a new concept to fine-tune the Dzyaloshinskii-Moriya interaction (DMI) by manipulating the degree of electronic asymmetry at the interfaces of a heavy metal/ferromagnet thin film through modification of the electric interface dipole by the adsoption of electronegative ions at the surface
Besides DMI, we explain in addition how other magnetic interactions, i.e. exchange interaction and the magnetocrystalline anisotropy energy (MAE), at such transition-metal interfaces are modified in the presence of oxygen

Summary

Introduction

Systems with broken spatial inversion symmetry present a fascinating playground for the design of thought-intriguing ferroic behaviors[1] and the emergence of unexpected transport phenomena[2]. Numerical studies have demonstrated the seminal role of spin-orbit coupling in the form of DMI in the emergence and stabilization of these chiral magnetic textures These magnet/heavy-metal interfaces are currently being intensively investigated from the standpoint of mainstream spintronics with the recent development of spin-orbit torques[18,19]. We validate this proposal by demonstrating that the magnitude and sign of the DMI of asymmetric ultrathin films can be widely tuned by controlling oxygen coverage We demonstrate this effect in detail for oxygen, there is no doubt that it is much more general and should apply to other ions whose electronegativity is larger than that of the heavy metal substrate, e.g. C, N, F, Cl, Br, I. This study reveals that in systems grown for technological use, which are typically capped by an oxide[34,36,38], such as MOx/FM/HM (FM a ferromagnet and MOx might be MgOx, AlOx, CoOx etc.), the DMI can be tuned by changing the oxidation conditions of the capping layer, offering a convenient way of control

Methods

Results

Conclusion