Gate-Controlled Skyrmions in Magnetic Trilayer Tracks

Abstract

Structural inversion asymmetry together with spin-orbit coupling can induce interfacial Dzyaloshinskii-Moriya Interaction (iDMI) in Heavy-Metal/Ferromagnet/Metal-Oxide heterostructuctures [1]. In such thin film systems with perpendicular magnetic anisotropy the iDMI combined with dipolar interactions can stabilize non-collinear chiral magnetic spin textures such as Néel Domain Walls (DWs), eventually forming magnetic skyrmion bubbles [2]. The iDMI amplitude and sign determine the spin texture of the DWs and their chirality [3]. Moreover, skyrmions can be moved by a current thanks to spin orbit torques, in a direction depending on their chirality.In this study we report on a deterministic control of their motion related to a chirality switch of magnetic skyrmion bubbles in Ta/FeCoB/TaOx trilayer, covered by a ZrO2 ionic conductor (Fig. 1a). Monitored under a polar-Magneto-Optical Kerr-Effect (p-MOKE) microscope we apply a gate voltage through a transparent Indium Tin Oxide (ITO) electrode and demonstrate by real space tracking the reversal of their current-induced motion (Fig. 1b). Micromagnetic simulations together with similar measurements on magnetic domain walls confirm the possibility to invert the chirality, eventually leading to versatile spintronic and logic devices.We have furthermore optimized the fabrication of skyrmion Hall-bar tracks (Fig. 2a), containing magnetic skyrmion bubbles (Fig. 2b), with deported ITO top electrodes. These skyrmion racetracks of different shapes and sizes allow to assess the effect of gate voltage and lateral confinement on the skyrmion motion. Eventually, the gate would play the role of a pinning potential and control the skyrmion velocity. In a similar Hall-bar geometry with multiple Hall-contacts we envision to demonstrate the electrical tracking of a moving skyrmion in replacement for the MOKE images that are limited in temporal and spatial resolution.   Gate-Controlled Skyrmions in Magnetic Trilayer Tracks