Magnetic skyrmion nucleation via current injection in confined nanotrack with modified perpendicular anisotropy region

Magnetic skyrmions, as spintronic information carriers, are promising for next-generation spin logic and memory devices. For such skyrmion-based devices, effective control of skyrmion nucleation and controllable motion in the nanotrack are of great importance. The ion irradiation process can modify magnetic properties, such as perpendicular magnetic anisotropy (PMA) and Dzyaloshinskii-Moriya interaction (DMI), at the nanoscale, which can be used to reduce the design complexity of devices. In this study, a nanoregion without PMA in the nanotrack is adopted as a skyrmion nucleation seed and a current-driven highly efficient, in-line, and on-demand skyrmion nucleation schematic is presented. A key factor for realizing this concept is that the disappearance of PMA and the existence of DMI induce magnetization tilts and create a chiral perpendicular stripe domain within the nucleation region. This stripe domain allows the effective control of the spin transfer torque, and it is ejected from the PMA-modified region and propelled into the nanotrack, forming a stable skyrmion. Our proposed device allows the controlled nucleation and propagation of a series of skyrmions, which allows binary information to be written in a controlled manner, consequently, yielding simple devices with two terminals. This study provides an efficient route for designing tunable skyrmionics-mechanic memory devices.