The reliable estimation of the spin-orbital-torque (SOT) efficiency in ferromagnetic multilayers with small coercive force is a nontrivial task, but extremely demanded for implementation of current-induced magnetization reversal memory cells. Here, we report on results of an experimental study of current-induced magnetization reversal of the $\mathrm{Ru}/\mathrm{Co}/\mathrm{Ru}$ and $\mathrm{Ru}/\mathrm{Co}/\mathrm{Ru}/\mathrm{W}$ structures. In the considered structures, because of the small value of the coercive force comparable in magnitude to the Oersted field and the SOT effect field, the magnetization reversal is carried out by moving a domain wall parallel to the direction of current injection. For such a case, an alternative method for estimating the effective field of SOT based on the analysis of the domain-wall position considering the distribution of the Oersted field is proposed. This method allows us to determine the effective longitudinal field ${\mu }_0{H}_L/j=1.6\times {10}^{-11}\mathrm{mT/A}{\mathrm{m}}^{-2}$ and the efficiency of SOT ${\xi }_L=0.03$ in the quasisymmetric $\mathrm{Ru}/\mathrm{Co}/\mathrm{Ru}$ structure. An addition of a capping layer of $\mathrm{W}$ enhances ${\xi }_L$ by 5 times.

• Received 2 January 2019
• Revised 17 April 2019

DOI:https://doi.org/10.1103/PhysRevApplied.11.054047