Engineering Domain-Wall Motion in Co−Fe−B/MgO Ultrathin Films with Perpendicular Anisotropy Using Patterned Substrates with Subnanometer Step Modulation

Controlling the motion of magnetic domain walls (DWs) in ultrathin films with perpendicular magnetic anisotropy (PMA) has opened perspectives for mass-storage applications such as ``racetrack memory''. However, a crucial issue for this technology is to efficiently move and store domain walls along very narrow wires. The authors' approach uses prepatterned substrates with regularly spaced nanoscale steps to grow high-quality films with PMA. The very low steps act as efficient pinning sites when DWs move $a\phantom{\rule{0}{0ex}}c\phantom{\rule{0}{0ex}}r\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}s\phantom{\rule{0}{0ex}}s$ them, yet as very efficient conduits when DWs move $a\phantom{\rule{0}{0ex}}l\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}g$ them. This may be a promising solution to crucial problems concerning edge damage at very small wire dimensions.