Magnetic skyrmion, as one of the topologically protected spin textures stabilized in the materials with perpendicular magnetic anisotropy (PMA) and interfacial Dzyaloshinskii-Moriya interaction (iDMI), are quite small in the nanometer size and can be driven by spin torque with lower current density, which provide a reliable technique for use in next-generation racetrack memory, logical devices, spin transfer nano-oscillator, etc. Magnetic skyrmion in the above applications are mainly based on the controllable motion of skyrmions in the confined geometrics. Furthermore, a controllable, reproducible, and realized skyrmion nucleation is another most important elements in such skyrmion-based devices. Several researchers have proposed and demonstrated skyrmion nucleation schemes, such as, patterning the magnetic structures with notches or defects, domain wall transfer or chopping to skyrmions. However, all these methods include significant structural or even geometrical modifications of the magnetic racetrack which increasing the devices design complexity. Recently works have shown that sputtering process can control magnetic properties, such as PMA and DMI, at the nanoscale. In this work, we adopted a nanoregion without PMA as a skyrmion nucleation core and demonstrate a current driven highly efficient, in-line and on-demand skyrmion nucleation schematic. Fig. 1(a) shows an illustration of skyrmion nucleation devices considered here. One key factor for realizing this is that the vanishing of the PMA and the existing of the DMI induced magnetization tilt and create a chiral perpendicular stripe domain wall at left edges. This stripe domain wall that allows spin torque to efficiently controlled and ejected from the modified region and propelled into the nanowire to form a skyrmion. As shown in Fig. 1(b), this device integrated both skyrmion nucleation and control function is more advantages in simply the devices with two terminals. This working mode could be controlled by the selective current pulse sequence with one for nucleation and another one for shifting which is important to skyrmion-based racetrack memory applications.

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