Spin-orbit torque efficiency enhancement to tungsten-based SOT-MTJs by interface modification with an ultrathin MgO

The effect of the MgO interlayer in the W/CoFeB interface on the charge-to-spin current conversion efficiency was experimentally investigated by changing the MgO interlayer thicknesses. Experimental results show high |ξdl| up to 0.58 by introducing a 0.22-nm-thick MgO interlayer, which is 45% enhanced as compared to the one without the MgO interlayer. The switching current density in the corresponding MTJs was also reduced by nearly 48% under 1-ns-width pulse tests. The improved switching efficiency can be explained by the enhanced Rashba effect at the W/MgO interface theoretically. In summary, these findings give potential solutions to the high-power dissipation issue for the tungsten-based SOT-MTJs.