Boosting domain wall propagation by notches

We report a counterintuitive 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 nonadiabatic spin-transfer torque strength beta is smaller than the Gilbert damping constant alpha. The boost can be multifold. (3) DW propagation velocity is hindered when beta > alpha. The results are explained by using the Thiele equation.