Direct Observation of Massless Domain Wall Dynamics in Nanostripes with Perpendicular Magnetic Anisotropy

TL;DR

This study demonstrates that domain walls in nanostripes with perpendicular magnetic anisotropy exhibit negligible inertia during current-induced motion, enabling precise control through pulse tuning due to their very low effective mass.

Contribution

The paper provides direct observation of massless domain wall dynamics in nanostripes with perpendicular magnetic anisotropy, highlighting their negligible inertia and potential for accurate manipulation.

Findings

Domain walls start moving immediately at constant current amplitude.

Minimal or no motion occurs after current pulse ends.

Low domain wall mass attributed to narrow width and high damping.

Abstract

Domain wall motion induced by nanosecond current pulses in nanostripes with perpendicular magnetic anisotropy (Pt/Co/AlO$_x$) is shown to exhibit negligible inertia. Time-resolved magnetic microscopy during current pulses reveals that the domain walls start moving, with a constant speed, as soon as the current reaches a constant amplitude, and no or little motion takes place after the end of the pulse. The very low 'mass' of these domain walls is attributed to the combination of their narrow width and high damping parameter $\alpha$. Such a small inertia should allow accurate control of domain wall motion, by tuning the duration and amplitude of the current pulses.