Lower switching-current density in Ta/(Pt/X)n/Pt/Co/Ta (X = Ta,Mn,Cu,V,Zr, Bi; n = 3, 4) multilayers based on a domain-wall-depinning model

In recent years, spin-orbit torque (SOT) generated by heavy metal (HM) has garnered increasing attention. However, SOT-magnetic random-access memory based on HM suffers from a low spin Hall angle and high current density. Here, we demonstrate that the critical switching-current density ($I_c$) in a multilayer structure of $\mathrm{Ta}/(\mathrm{Pt}/\mathrm{Ta}{)}_4/\mathrm{Pt}/\mathrm{Co}/\mathrm{Ta}$ has been reduced by 79% compared with that of $\mathrm{Ta}/\mathrm{Pt}/\mathrm{Co}/\mathrm{Ta}$, achieving a value of 5.88 × ${10}^6\mathrm{A}/{\mathrm{cm}}^2$. This value is considerably low among all reported values in the $\mathrm{Pt}/\mathrm{Co}$ system literature. The reduction of $I_c$ is accompanied by enhanced dampinglike torque efficiency (${\beta }_D$) and reduced coercive force ($H_c$). A perfect linear correlation has been observed between $I_c$ and $H_c$/${\beta }_D$, which supports the domain-wall depinning model of the SOT-induced magnetization reversal in this system. Crucially, this linearity extends to several metal dopants possessing the identical superlattice structure. This research offers insights into the future of low-power, high-density magnetic memory technology based on HM materials.