Thickness dependence of current-induced domain wall motion in a Co/Ni multi-layer with out-of-plane anisotropy

Thickness dependence of current-induced domain wall (DW) motion in a perpendicularly magnetized [Co/Ni](N) multilayered wire containing Ta/Pt capping and Pt/Ta seed layers has been studied. The thickness of the magnetic layer was controlled by the stacking number, N. The threshold current density for driving DW had a local minimum at N = 3 and the velocity of DW motion decreased with N. Estimation of carrier spin polarization from measurements of DW velocity revealed that a thinner Co/Ni stack adjacent to the Pt layers reduced the carrier spin polarization and the strength of adiabatic spin transfer torque. (C) 2013 AIP Publishing LLC [http://dx.doi.org/10.1063/1.4802266]