Spin orbit torques and Dzyaloshinskii-Moriya interaction in dual-interfaced Co-Ni multilayers

Jiawei Yu,Xuepeng Qiu,Jungbum Yoon,Aurelien Manchon,Praveen Deorani,Jean Mourad Besbas,Hyunsoo Yang,Yang Wu

doi:10.1038/srep32629

Abstract

We study the spin orbit torque (SOT) and Dzyaloshinskii-Moriya interaction (DMI) in the dual-interfaced Co-Ni perpendicular multilayers. Through the combination of top and bottom layer materials (Pt, Ta, MgO and Cu), SOT and DMI are efficiently manipulated due to an enhancement or cancellation of the top and bottom contributions. However, SOT is found to originate mostly from the bulk of a heavy metal (HM), while DMI is more of interfacial origin. In addition, we find that the direction of the domain wall (DW) motion can be either along or against the electron flow depending on the DW tilting angle when there is a large DMI. Such an abnormal DW motion induces a large assist field required for hysteretic magnetization reversal. Our results provide insight into the role of DMI in SOT driven magnetization switching, and demonstrate the feasibility of achieving desirable SOT and DMI for spintronic devices.

Highlights

Current induced domain wall (DW) nucleation, fast DW motion[1,2,3,4,5] and highly efficient magnetization switching[6,7,8] have recently been reported in heavy metal (HM)/FM heterostructures
A fine understanding of the different contributions of the top and bottom interfaces to the spin orbit torque (SOT) and Dzyaloshinskii-Moriya interaction (DMI) is crucial to such achievements
It should be noted that we consider the current shunting effect in the calculation of SOT effective fields, and we normalize HL/T in each HM layer with their own current density

Summary

Introduction

Current induced domain wall (DW) nucleation, fast DW motion[1,2,3,4,5] and highly efficient magnetization switching[6,7,8] have recently been reported in HM/FM heterostructures. Depending on the choice of capping layer X, one can expect an enhancement or cancellation of these two SOT contributions[26], which provides an interesting prospect for obtaining larger SOT and efficient current-induced magnetization switching through a proper combination of materials in structure engineering. As reported in recent works, the magnitude and sign of DMI can be changed by using different underlayer materials[23,24,33] and the induced Néel wall with different chiralities can be driven efficiently in different directions by the SHE5,21,22. We experimentally reveal that a large negative DMI can result in abnormal current induced switching behaviors preventing full hysteretic magnetization reversal This demonstrates the distinct roles played by the DMI and SOT in the current-driven switching, and indicates pathways towards the improvement of switching properties of these devices. All these properties make the Co-Ni multilayer system a suitable choice to carry out the studies of different capping layers

Methods

Results

Conclusion