Magnetic domain wall motion with current perpendicular to the plane spin transfer torque

Abstract

In this paper we discuss current-driven magnetic domain wall (DW) dynamics in ferromagnetic nanowires in the current-perpendicular-to-plane geometry. We show that spin transfer torque from direct spin-polarized current applied parallel to a magnetic domain wall induces DW motion in a direction independent of the current polarity. This unidirectional response of the DWto spin torque enables DWpumping - long-range DWdisplacement driven by alternating current. Our numerical simulations reveal that DW pumping can be resonantly amplified through excitation of internal degrees of freedom of the DW by the current. We also experimentally study the interactions of spin-torque with a domain wall. We resonantly excite high-speed motion of a domain wall trapped at a pinning site and observe velocities over 800 m/s at current densities below 10⁷ A/cm².