Tailoring magnetic energies to form dipole skyrmions and skyrmion lattices

Montoya, Sergio; Couture, S.; Chess, Jordan; Lee, J. C. T.; Kent, Noah; Henze, D.; Sinha, Sunil K.; Im, Mi‐Young; Kevan, S. D.; Fischer, Peter; McMorran, Benjamin; Lomakin, Vitaliy; Roy, Sujoy; Fullerton, Eric E.

doi:10.1103/physrevb.95.024415

Cited by 180 publications

(173 citation statements)

References 61 publications

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“…We demonstrate the realization of an ordered magnetic skyrmion lattice in amorphous multilayer thin-films without DM interactions. These skyrmions have been suggested to be stabilized by dipole-dipole interactions, 19,20 but recent works have suggested a random anisotropy (RA) specific to amorphous and nanocrystalline systems may also contribute to skyrmion formation 21 . Utilizing a straight forward magnetic field sequence (presented in Supplemental Fig.…”

Section: Introductionmentioning

confidence: 99%

Realization of ordered magnetic skyrmions in thin films at ambient conditions

Desautels

DeBeer‐Schmitt²,

Montoya

et al. 2019

Phys. Rev. Materials

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Magnetic skyrmions present interesting physics due to their topological nature and hold significant promise for future information technologies. A key barrier to realizing skyrmion devices has been stabilizing these spin structures under ambient conditions. In this manuscript, we exploit the tunable magnetic properties of amorphous Fe/Gd mulitlayers to realize skyrmion lattices which are stable over a large temperature and magnetic field parameter space, including room temperature and zero magnetic field. These hybrid skyrmions have both Bloch-type and Néel-type character and are stabilized by dipolar interactions rather than Dzyaloshinskii-Moriya interactions, which are typically considered required for the generation of skyrmions. Small angle neutron scattering (SANS) was used in combination with soft X-ray microscopy to provide a unique, multi-scale probe of the local and long-range order of these structures. These results identify a pathway to engineer controllable skyrmion phases in thin film geometries which are stable at ambient conditions.

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Section: Introductionmentioning

confidence: 99%

Realization of ordered magnetic skyrmions in thin films at ambient conditions

Desautels

DeBeer‐Schmitt²,

Montoya

et al. 2019

Phys. Rev. Materials

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“…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 skyrmions with a fixed helicity, SKBs in centrosymmetric magnets possess two degrees of freedom, i.e., vorticity and helicity, 35 which makes them usually coexist with the topologically trivial bubbles (topological number is equal to 0), [28][29][30][31]37 or exhibit multiple topologies such as biskyrmions, 25,27,30,36 and various metastable SKBs 28,30,36 (for example, pendulum-shaped SKBs 29 and bifurcation-shaped SKBs 28,30,36 ).When external stimuli, such as magnetic field H or spin-polarized current, are applied, the spin structures of the trivial and metastable SKBs may vary with the motion of Bloch lines (BLs), making them unsuitable for the application in magnetic racetrack memory devices.Therefore, in order to be suitable for such applications, it is essential to remove trivial bubbles and metastable SKBs. 21Recent theoretical simulations, based on the nanostructured frustrated magnet, showed that the periodically modulated spin textures at geometrical boundaries had a significant influence on the magnetization dynamics of SKBs , 35 offering a new path that designing proper…”

mentioning

confidence: 99%

“…Contrary to DMI-stabilized skyrmions with a fixed helicity, SKBs in centrosymmetric magnets possess two degrees of freedom, i.e., vorticity and helicity, 35 which makes them usually coexist with the topologically trivial bubbles (topological number is equal to 0), [28][29][30][31]37 or exhibit multiple topologies such as biskyrmions, 25,27,30,36 and various metastable SKBs 28,30,36 (for example, pendulum-shaped SKBs 29 and bifurcation-shaped SKBs 28,30,36 ).…”

mentioning

confidence: 99%

Manipulating the Topology of Nanoscale Skyrmion Bubbles by Spatially Geometric Confinement

Hou

Zhang

et al. 2019

ACS Nano

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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...

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“…To move beyond dislocations and disclinations in wPMA materials, alternative strategies would be required, and they have only begun to be explored. This has been done, for example, by the application of out-of-plane magnetic fields in order to drive a transition from stripe pattern to dipolar skyrmion in amorphous Fe/Gd multilayers [31]. Other possibilities could be based in domain imprinting, as it is often done in multilayers that combine in-plane and out-of-plane anisotropy layers [16], or in geometrical confinement by sample patterning [32].…”

Section: Introductionmentioning

confidence: 99%

Topological defects in weak perpendicular magnetic anisotropy NdCo honeycomb lattices

et al. 2018

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Domain configuration has been studied by magnetic force microscopy and micromagnetic simulations in NdCo honeycomb lattices in comparison with similar patterned structures made of polycrystalline Co. The change in material anisotropy from in-plane to weak perpendicular magnetic anisotropy (wPMA) modifies the basic domain structure and relevant topological defects in the magnetization in each case: from in-plane domains, vortices, antivortices and half vortices in Co lattices to parallel stripe patterns with dislocations in NdCo samples with large enough thickness. A characteristic feature of wPMA materials is the possibility to drive the system from in-plane to stripe pattern configuration playing with sample thickness (during growth) or with magnetic anisotropy (as a function of temperature). It has allowed us to observe complex magnetic textures within the stripe pattern of NdCo samples imprinted from previous magnetic vortex and antivortex states that nucleate within the honeycomb lattice during the early stages of deposition and, then, become frozen by local rotatable anisotropy as sample thickness increases.

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Tailoring magnetic energies to form dipole skyrmions and skyrmion lattices

Cited by 180 publications

References 61 publications

Realization of ordered magnetic skyrmions in thin films at ambient conditions

Realization of ordered magnetic skyrmions in thin films at ambient conditions

Manipulating the Topology of Nanoscale Skyrmion Bubbles by Spatially Geometric Confinement

Topological defects in weak perpendicular magnetic anisotropy NdCo honeycomb lattices

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