Stack Structure Dependence of Co/Ni Multilayer for Current-Induced Domain Wall Motion

We developed a film stack structure of Co/Ni with perpendicular magnetic anisotropy (PMA), which is suitable for current-induced domain wall (DW) motion. A Ta/Pt underlayer effectively provided a sufficiently large PMA to achieve the DW motion driven by a small current. The critical current density (j(c)) had a minimum value at a Pt underlayer thickness (t(UL)) of 2.4 nm and was insensitive to cap layer thickness (t(cap)). The dependence of jc on tUL and tcap can be accounted for in terms of the effective spin polarization. (C) 2010 The Japan Society of Applied Physics