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.Comment: 32 pages, 11 figure
