Stabilization and dynamical switching of skyrmions and skyrmioniums in magnetic hemispherical shells

다국어 초록 (Multilingual Abstract)

We explored the topological magnetic textures of vortices, skyrmions, and skyrmioniums in magnetic hemispherical shells by varying surface-normal uniaxial magnetic anisotropy constant (Ku), Dzyaloshinskii-Moriya interaction (DMI) constant (Dint), and the shell diameter 2R. For given values of 2R, the combination of Ku and Dint plays a crucial role in the stabilization of those different spin textures. With decreasing 2R, the geometrical confinement of hemispherical shells more significantly affects the stabilization of skyrmions owing to curvature-induced DM-like interaction. This effect is contrastingly dependent on the sign of Dint: skyrmion formation is more favorable for positive Dint values, whereas it is less favorable for negative ones. A quite promising feature is that skyrmions can be stabilized even in the absence of intrinsic DMI for 2R < 25 nm. We also explored characteristic dynamic properties of skyrmions excited by in-plane and out-of plane oscillating magnetic fields. Similar to the fundamental dynamic modes found in planar dots, in-plane gyration and azimuthal spin-wave modes as well as out-of-plane breathing modes were found, but additional higher-frequency hybrid modes also appeared due to coupling between radially quantized and azimuthal spin-wave modes. Finally, we found a switching behavior of skyrmion polarity through a transient skyrmionium state using very-low-strength AC magnetic fields. This work provides further physical insight into the static and dynamic properties of skyrmions in curved-geometry nanodots and suggests potential applications to low-power consumption and ultra-high-density information-storage devices.