Stability and formation of skyrmion in ferromagnetic nanodots ~20 nm lateral dimensions with high M_sand moderate DMI

Voltage Controlled Magnetic Anisotropy (VCMA) induced skyrmion mediated reversal of ferromagnet has been experimentally shown to be robust and energy efficient (~1 fJ/bit) while not requiring a bias magnetic field. While this scheme could lead to Magnetic Tunnel Junctions (MTJs) based devices [1,2], scalability could be an issue as ferromagnetic skyrmions ~20 nm cannot be formed with experimentally observed Dzyaloshinskii-Moriya interaction (DMI) [3]. Though small skyrmions ~10 nm can be formed in ferrimagnets due to their low saturation magnetization (M_s), it is only possible in infinite films and racetracks whose dimensions are much larger than those of the skyrmions [4]. In this study, we show with micromagnetic simulation that small ferromagnetic skyrmion ~20 nm size in patterned nanostructures can be formed by increasing M_s for experimentally available DMI, as opposed to following the trend of lowering M_s and forming small skyrmion in ferrimagnetic racetrack/infinite films.

[1] D. Bhattacharya, et al., Nat Electronics 3, 539–545 (2020)
[2] D. Bhattacharya and J. Atulasimha, ACS Appl. Mater. Interfaces, 10, 20, 17455 (2018)
[3] M.M. Rajib et al., IEEE TED, 67, 9,3883-3888 (2020)
[4] L. Caretta et al., Nature Nano., 13, 1154-1160 (2018)