Role of B diffusion in the interfacial Dzyaloshinskii-Moriya interaction inTa/Co20Fe60B20/MgOnanowires

We report on current-induced domain wall motion in $\mathrm{Ta}/\mathrm{C}{\mathrm{o}}_{20}\mathrm{F}{\mathrm{e}}_{60}{\mathrm{B}}_{20}/\mathrm{MgO}$ nanowires. Domain walls are observed to move against the electron flow when no magnetic field is applied, while a field along the nanowires strongly affects the domain wall motion velocity. A symmetric effect is observed for up-down and down-up domain walls. This indicates the presence of right-handed domain walls, due to a Dzyaloshinskii-Moriya interaction (DMI) with a DMI coefficient $D=+0.06\phantom{\rule{0.16em}{0ex}}\mathrm{mJ}/{\mathrm{m}}^{2}$. The positive DMI coefficient is interpreted to be a consequence of B diffusion into the Ta bu…