Chirality Switch of Magnetic Skyrmion in Ta/FeCoB/TaOx Trilayers

Abstract

Magnetic skyrmions [1] are promising candidates for next-generation spintronic devices. Their solitonic and chiral nature allows an efficient current-induced motion up to high velocities [2]. A fine tuning of their chirality would enable highly-manipulable magnetic skyrmions, which paves the way for new functionalities in spintronic memory, logic and neuromorphic devices [3,4]. This gives great importance to the control of the interfacial Dzyaloshinskii-Moriya interaction (iDMI) [5,6] strength and sign, at the origin of magnetic skyrmions and their chirality. In this study, we directly demonstrate magnetic skyrmion’s chirality switching in a Ta/FeCoB/TaOx trilayer. In fact, by varying the thickness of FeCoB and the oxidation state at the FeCoB/TaOx interface, we are able to obtain different regions in which magnetic skyrmions are right-handed (iDMI>0) or left-handed (iDMI<0) (resp. regions #4 and #2 on Fig.1). This material-dependent chirality switching brings a new degree of freedom to the exciting physics of magnetic skyrmions. For the first time, we show that the iDMI sign crossover in the different regions, as measured by Brillouin-Light-Scattering (BLS), is accompanied by a change of skyrmion chirality, as confirmed by the opposite direction of current-induced motion of magnetic skyrmions (See Fig. 2). Notably, between the two regions of opposite iDMI sign we have found, as expected, a region where iDMI∼0. In this region, the control of the iDMI with an electric field [7] may lead to a voltage-induced chirality switching, which hasn’t been observed yet. This all-electrical control of magnetic skyrmions represents a cornerstone towards power efficient spintronic devices and multidirectional logic functionnalities.