Abstract
The influence of C insertion on Dzyaloshinskii–Moriya interaction (DMI) as well as current-induced domain wall (DW) motion (CIDWM) and tilting in Pt/Co/Ta racetracks is investigated via a magneto-optical Kerr microscope. The similar DMI strength for Pt/Co/Ta and Pt/Co/C/Ta samples reveals that DMI mainly comes from the Pt/Co interface. Fast DW velocity around tens of m/s with current density around several MA/cm2 is observed in Pt/Co/Ta. However, it needs double times larger current density to reach the same magnitude in Pt/Co/C/Ta, indicating DW velocity is related to the spin-orbit torque efficiency and pinning potential barrier. Moreover, in CIDWM, DW velocity is around 103 times larger than that in field-induced DW motion (FIDWM) with current-generated effective field keeping the same magnitude as applied magnetic field, revealing that the current-generated Joule heating has an influence on DW motion. Interestingly, current-induced DW tilting phenomenon is observed, while this phenomenon is absent in FIDWM, demonstrating that the current-generated Oersted field may also play an essential role in DW tilting. These findings could provide some designing prospects to drive DW motion in SOT-based racetrack memories.
Highlights
Current-induced magnetic domain wall motion (CIDWM) in racetracks has revealed a newly developing magnetic racetrack memory device [1, 2]
It is noted that both the bottom Pt/Co and top Co/Ta interfaces contribute to the Dzyaloshinskii–Moriya interaction (DMI) but may partially cancel each other [28], leading to the slightly decreased |D| for Pt/Co/Ta samples compared to Pt/Co/C/Ta samples
The similar |D| for Pt/Co/Ta and Pt/Co/ C/Ta samples reveals that the DMI strength mainly comes from the contribution of the Pt/Co interface
Summary
Current-induced magnetic domain wall motion (CIDWM) in racetracks has revealed a newly developing magnetic racetrack memory device [1, 2]. Owing to this promising prospect, lots of work have been carried out during the last few decades. CIDWM was firstly investigated in ferromagnets (FMs) with in-plane magnetic anisotropy and the spin-polarized current-generated spin transfer torque (STT) acts as the driving force [3, 4]. Afterwards, CIDWM was realized in FMs with perpendicular magnetic anisotropy (PMA) [5, 6]. In some PMA materials, domain wall (DW) motion direction is opposite to the direction of the electron flow, which is contradictory to the prediction of STT [7, 8]. Much more works are found that DW motion is along the current direction in
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