Manipulating the Topology of Nanoscale Skyrmion Bubbles by Spatially Geometric Confinement

Abstract

The discovery of magnetic skyrmion bubbles in centrosymmetric magnets has been receiving increasing interest from the research community, due to the fascinating physics of topological spin textures and its possible applications to spintronics. However, key challenges remain, such as how to manipulate the nucleation of skyrmion bubbles to exclude the trivial bubbles or metastable skyrmion bubbles that usually coexist with skyrmion bubbles in the centrosymmetric magnets. Here, we report having successfully performed this task by applying spatially geometric confinement to a centrosymmetric frustrated Fe 3 Sn 2 magnet. We demonstrate that the spatially geometric confinement can indeed stabilize the skyrmion bubbles, by effectively suppressing the formation of trivial bubbles and metastable skyrmion bubbles. We also show that the critical magnetic field for the nucleation of the skyrmion bubbles in the confined Fe 3 Sn 2 nanostripes is drastically less, by an order of magnitude, than that what is required in the thin plate without geometrical confinement. By analyzing how the width and thickness of the nanostripes affect the spin textures of skyrmion bubbles, we infer that the topological transition of skyrmion bubbles is closely related to the dipole-dipole interaction, which we find is consistent with theoretical simulations. The results presented here represent an important step forward in manipulating the topological spin textures of skyrmion bubbles, making us closer to achieving the fabrication of skyrmion-based racetrack memory devices.Magnetic skyrmions are topologically protected vortex-like objects that were first discovered in the chiral, non-centrosymmetric magnets 1-6 where they are stabilized by the Dzyaloshinskii-Moriya interaction (DMI). Unlike the conventional, "rigid" magnetic domain walls, they are flexible in shape-deformation to avoid pinning centres, 7,8 and therefore only an ultra-low current density is needed to drive them to move. 7-12 This fascinating topological property, combined with their nanoscale size and stable particle-like features make skyrmions promising candidate for carrying magnetic information in further high-density and low-power consumption spintronic devices based on the racetrack memory concept. 8,13,[14][15][16][17][18][19][20][21][22][23][24] Recent studies showed that some non-chiral centrosymmetric magnets could host skyrmion bubbles (SKBs), 25-32 stabilized by the interplay of the external magnetic field, ferromagnetic exchange interaction, uniaxial magnetic anisotropy, and dipole-dipole interaction (DDI). SKBs are topologically equivalent to magnetic skyrmions and exhibit similar topological properties, such as the topological Hall effect, 27 skyrmion Hall effect, 33 and ultra-low driving current density for current-induced motion. 25 More importantly, SKBs show a significantly high thermal stability over a wide temperature range crossing room temperature, 27,28,34 showing a high potential of SKBs for the construction of memory devices.Contrary to DMI-stabilized skyr...

Electric-field-driven non-volatile multi-state switching of individual skyrmions in a multiferroic heterostructure

“…However, few skyrmions are retained at zero magnetic field. This feature further suggests that the magnetic hysteretic effect in our experiments mainly originates from the geometrical pinning effect of the nano-dots, as reported in the previous literatures 9 , 39 , 40 . For the non-volatility of vortex, the case is different.…”

Recent Progress on Topological Structures in Ferroic Thin Films and Heterostructures

“…[ 98,99 ] In 2017, Hou et al first experimentally observed skyrmionic magnetic bubbles at room temperature in a frustrated Fe 3 Sn 2 magnet with Kagome lattice by using LTEM (Figure 2f–h). [ 129,130 ] In 2019, Kurumaji et al. demonstrated a Bloch‐type skyrmion state in a frustrated centrosymmetric triangular‐lattice magnet Gd 2 PdSi 3 .…”

Large anisotropic topological Hall effect in a hexagonal non-collinear magnet Fe5Sn3

“…There are five types of alloys in the Fe-Sn compounds family, that is Fe3Sn, Fe5Sn3 and Fe3Sn2, FeSn, and FeSn2, and all of these alloys show a magnetic ordering temperature well above the RT. Among these alloys, the frustrated kagome magnet Fe3Sn2 have emerged as an important class of the magnetic topological materials in recent years because it exhibits many interesting physical properties, such as skyrmions [31][32][33][34] , massive Dirac fermions 35 , many-body spin-orbit tunability 36 , flatbands 37 , de-Haas-Van Alphen effect 38 , and the large THE above the RT 16 . Furthermore, the kagome antiferromagnetic FeSn also exhibits profound relation with some interesting physical properties such as Dirac fermions and flatbands 39 .…”