Boosting Domain Wall Propagation by Notches

We report a counter-intuitive finding that notches in an otherwise homogeneous magnetic nanowire can boost current-induced domain wall (DW) propagation. DW motion in notch-modulated wires can be classified into three phases: 1) A DW is pinned around a notch when the current density is below the depinning current density. 2) DW propagation velocity is boosted by notches above the depinning current density and when non-adiabatic spin-transfer torque strength $\beta$ is smaller than the Gilbert damping constant $\alpha$. The boost can be manyfold. 3) DW propagation velocity is hindered when $\beta > \alpha$. The results are explained by using the Thiele equation.