Domain wall dynamics under electric field in Ta/Co40Fe40B20/MgO devices with perpendicular anisotropy

Electric field effect (EFE) in ferromagnetic/oxide dielectric structures provides a new route to control domain wall (DW) dynamics with low power dissipation. However, EFE on DW velocity has been only observed so far in the creep regime where DW velocity is low due to a strong interaction with pinning sites. Our approach makes use of CoFeB-MgO films with perpendicular magnetic anisotropy (PMA), which are considered as the most promising not only for STT-RAM but also for DW based memories, since a combination of spin Hall effect and Dzyaloshinskii-Moriya interaction could lead to efficient DW motion under current. Using NV center microscopy to map DW pinning along a magnetic wire, we first show¹ that Ta/Co₄₀Fe₄₀B₂₀(1nm)/MgO structures exhibit a very low density of pinning defects with respect to others materials with PMA. Then we show² gate voltage modulation of DW velocity from the creep to the flow regime with velocities up to 20 m s^-1. We demonstrate a universal description of EFE over the full range of DW dynamics by taking into account an effective magnetic field being linear with the electric field. In addition to our previous approach of using strain³, this work opens new opportunities for the study and optimization of electric field effect at ferromagnetic metal/insulator interfaces.