Target Bubbles in Fe₃Sn₂ Nanodisks at Zero Magnetic Field

Abstract

We report a vortex-like magnetic configuration in uniaxial ferromagnet Fe3Sn2 nanodisks using differential phase contrast scanning transmission electron microscopy. This magnetic configuration is transferred from a conventional magnetic vortex using a zero-magnetic-field warming process and is characterized by a series of concentric cylinder domains. We termed them as “target bubbles” that are identified as three-dimensional depth-modulated magnetic objects in combination with numerical simulations. Target bubbles have room-temperature stability even at zero magnetic field and multiple stable magnetic configurations. These advantages render the target bubble an ideal bit to be an information carrier and can advance magnetic target bubbles toward functionalities in the long term by incorporating emergent degrees of freedom and purely electrically controllable magnetism.

Current‐Controlled Topological Magnetic Transformations in a Nanostructured Kagome Magnet

“…Owing to different formation mechanisms of skyrmions and bubbles, skyrmions and bubbles are the only stable phases at normal field and large tilted field, respectively. [ 26–32 ] Therefore, for the Fe 3 Sn 2 thin plate, the controlled current‐induced skyrmion−bubble transformations can be realized in an intermediate tilted angular range ( Figure a), such as from ≈0.8° to 3.0° at B ≈ 500 mT. Although skyrmions can be metastable phases even at zero field, bubbles merge together to form a long stripe domain in the low field region at B ≤ 400 mT.…”

“…[ 38,39 ] The formation of magnetic objects in Fe 3 Sn 2 originates from the competition of uniaxial anisotropy, dipole–dipole interaction, and Zeeman energy. [ 26,27 ] Skyrmions with closure domain wall magnetizations are typically stabilized at a normal field to minimize the dipole–dipole interaction. In contrast, under a tilted magnetic field, the domain wall magnetizations tend to align along the in‐plane components of magnetic field to minimize Zeeman energy, resulting in the formation of bubbles.…”

“…[ 41 ] Magnetic parameters are set based on the material Fe 3 Sn 2 with A = 8.25 pJ m −1 , K u = 54.5 kJ m −3 , and room‐temperature saturation magnetization M s = 622.7 kA m −1 . [ 26,27 ] The cell size was set at 2 × 2 × 3 nm 3 . The equilibrium spin configurations were obtained using the conjugate‐gradient method.…”

“…[ 12 ] The switching of topological magnetic charge can be realized by transformations between skyrmions with an integer charge Q and topologically trivial magnetic states with zero Q , such as ferromagnet, [ 13–17 ] helix or stripes, [ 18–25 ] and bubbles. [ 26–33 ] Previous studies have realized the current‐induced skyrmion‐ferromagnet transformations. [ 34,35 ] However, thus far, current‐induced skyrmion−stripe (or helix) and skyrmion−bubble transformations which occur along with the manipulation of topological charges in a reproducible and reversible way have not been experimentally demonstrated.…”

Magnetic Domain Structure in Ferromagnetic Kagome Metal DyMn6Sn6

“…In particular, the intrinsic magnetic interactions that occur in materials with kagome crystal is of great complexity and results in complicated magnetic domains, for example, a frustrated circumstance would occur and lead to noncollinear magnetic spin structure [5][6][7][8][9][10]. Recently, topologically nontrivial skyrmions have been predicted to generate in kagome crystal when the crystal owns both Heisenberg and Dzyaloshinskii-Moriya interactions [11][12][13], and finally, the skyrmion bubbles are experimented and reported in Fe 3 Sn 2 without any Dzyaloshinskii-Moriya interaction [14][15][16][17], showing that the uniaxial magnetic anisotropy in kagome crystal can play a vital role in stabilized novel spin structure. On the other hand, the magnetic and electronic structures in kagome crystals are highly entangled, making them show both fruitful spin-orbit and electronic corrected effects.…”