Systematic motion of magnetic domain walls in notched nanowires under ultra-short current pulses

TL;DR

This paper investigates how ultra-short current pulses can precisely manipulate magnetic domain walls in nanowires with defects, highlighting the importance of pulse shape and transient effects for accurate positioning at room temperature.

Contribution

It demonstrates that very short, well-shaped current pulses enable reliable domain wall positioning in notched nanowires, and explores transient effects influencing domain wall motion.

Findings

Precise domain wall positioning is achievable with short rise/fall time pulses.

Transient effects significantly influence domain wall motion, especially below a critical damping ratio.

Pulse shape and transient effects can be tuned to control domain wall displacement direction.

Abstract

The precise manipulation of transverse magnetic domain walls in finite/infinite nanowires with artificial defects under the influence of very short spin-polarized current pulses is investigated. We show that for a classical $3d$ ferromagnet material like Nickel, the exact positioning of the domain walls at room temperature is possible only for pulses with very short rise and fall time that move the domain wall reliably to nearest neighboring pinning position. The influence of the shape of the current pulse and of the transient effects on the phase diagram current-pulse length are discussed. We show that large transient effects appear even when $\alpha$=$\beta$, below a critical value, due to the domain wall distortion caused by the current pulse shape and the presence of the notches. The transient effects can oppose or amplify the spin-transfer torque (STT), depending on the ratio $\beta/\alpha$. This enlarges the physical comprehension of the DW motion under STT and opens the route to the DW displacement in both directions with unipolar currents.