Current-driven domain wall motion along ferromagnetic strips with periodically-modulated perpendicular anisotropy

TL;DR

This paper investigates how current-driven domain walls move along ferromagnetic strips with periodically modulated perpendicular anisotropy, showing improved speed and density for potential device applications through micromagnetic simulations.

Contribution

It introduces a novel approach using periodically modulated anisotropy to enhance current-driven domain wall motion and compares it with field-driven methods.

Findings

Current-driven motion outperforms field-driven in speed and density.

Periodic anisotropy creates energy minima that pin and guide domain walls.

Triangular anisotropy modulation enables bidirectional wall shifting.

Abstract

The dynamics of magnetic domain walls along ferromagnetic strips with spatially modulated perpendicular magnetic anisotropy is theoretically studied by means of micromagnetic simulations. Ferromagnetic layers with a periodic sawtooth profile of the anisotropy depict a well-defined set of energy minima where the walls are pinned in the absence of external stimuli, and favor the unidirectional propagation of domain walls. The performance of the current-driven domain wall motion along these ratchet-like systems is compared to the field-driven case. Our study indicates that the current-driven domain wall motion exhibits significant improvements with respect to the field-driven case in terms of bit shifting speed and storage density, and therefore, it is suggested for the development of novel devices. The feasibility of these current-driven ratchet devices is studied by means of realistic micromagnetic simulations and supported by a one-dimensional model updated to take into account the periodic sawthooth anisotropy profile. Finally, the current-driven domain wall motion is also evaluated in systems with a triangular modulation of the anisotropy designed to promote the bidirectional shifting of series of walls, a functionality that cannot be achieved by magnetic fields.