New Type of Stable Particlelike States in Chiral Magnets

Rybakov, Filipp N.; Борисов, А. A.; Blügel, Stefan; Kiselev, Nikolai S.

doi:10.1103/physrevlett.115.117201

Cited by 220 publications

(215 citation statements)

References 45 publications

(54 reference statements)

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“…Figure 6 shows the spin distribution in the center of the film of one of the skyrmions from the simulation. It shows a conventional skyrmion tube truncated at each end by chiral Block points, similar to the chiral bobbers predicted by Rybakov 20 . These short-length in-plane skyrmions are not stable in isolation, but are frozen in by the disorder.…”

Section: B Sanssupporting

confidence: 75%

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Neutron study of in-plane skyrmions in MnSi thin films

et al. 2017

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The magnetic structure of the in-plane skyrmions in epitaxial MnSi/Si(111) thin films is probed in three dimensions by the combination of polarized neutron reflectometry (PNR) and small angle neutron scattering (SANS). We demonstrate that skyrmions exist in a region of the phase diagram above at temperature of 10 K. PNR shows the skyrmions are confined to the middle of the film due to the potential well formed by the surface twists. However, SANS shows that there is considerable disorder within the plane indicating that the magnetic structure is a 2D skyrmion glass.

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Section: B Sanssupporting

confidence: 75%

“…In the case of magnetic nanostructures, anisotropy 17,18 and finite size effects 19,20 are two key mechanisms that give the skyrmion phase its robustness over a large temperature and field range. The latter likely plays the dominant role in creating stable skyrmions in free-standing chiral magnetic nano-crystals [21][22][23][24] .…”

Section: Introductionmentioning

confidence: 99%

Neutron study of in-plane skyrmions in MnSi thin films

et al. 2017

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“…in Fig. 9, where the saddle point expansion is expected to be valid, will likely be described by an unknown stationary point with modulations in the three dimensions [16][17][18].…”

Section: Phase Diagrammentioning

confidence: 99%

Stability of skyrmion textures and the role of thermal fluctuations in cubic helimagnets: A new intermediate phase at low temperature

Laliena

Campo

2017

Phys. Rev. B

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The stability of the four known stationary points of the cubic helimagnet energy functional: the ferromagnetic state, the conical helix, the conical helicoid, and the skyrmion lattice, is studied by solving the corresponding spectral problem. The only stable points are the ferromagnetic state at high magnetic field and the conical helix at low field, and there is no metastable state. Thermal fluctuations around the stationary point, included to quadratic order in the saddle point expansion, destabilize the conical helix in a region where the ferromagnetic state is unstable. Thus, a new intermediate phase appears which, in a region of the phase diagram, is a skyrmion lattice stabilized by thermal fluctuations. The skyrmion lattice lost the stability by lowering temperature, and a new intermediate phase of unknown type, presumably with three-dimensional modulations, appears in the lower temperature region.

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“…(Such maps are well known when T 2 represents a Brillouin zone in k-space, but the mathematics is identical.) This map is characterized by an integer Chern number Discussion: Previous theories on understanding the increased stability on skyrmions in thin films of non-centrosymmetric materials 10,14-16 focussed primarily on the changes in uniaxial magnetocrystalline anisotropy 13,27,28 with thickness, or on finite-size effects 29,30 . In fact, the latter can give rise to spin-textures more complicated than skyrmion crystals, with variations in all three directions.…”

Section: Helicity and Ferrotoroidic Momentmentioning

confidence: 99%

“…We use numerical methods for the analysis of phases with m = m(x, y) as described in Appendix C. Note that we do not consider states where m has non-trivial variations in all three coordinates; see, e.g., ref. 30.…”

Section: And (∇M)mentioning

confidence: 99%

Skyrmions in chiral magnets with Rashba and Dresselhaus spin-orbit coupling

2016

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Skyrmions are topological spin textures of interest for fundamental science and applications. Previous theoretical studies have focused on systems with broken bulk inversion symmetry, where skyrmions are stabilized by easy-axis anisotropy. We investigate here systems that break surfaceinversion symmetry, in addition to possible broken bulk inversion. This leads to two distinct Dzyaloshinskii-Moriya (DM) terms with strengths D ⊥ , arising from Rashba spin-orbit coupling (SOC), and D from Dresselhaus SOC. We show that skyrmions become progressively more stable with increasing D ⊥ /D , extending into the regime of easy-plane anisotropy. We find that the spin texture and topological charge density of skyrmions develops nontrivial spatial structure, with quantized topological charge in a unit cell given by a Chern number. Our results give a design principle for tuning Rashba SOC and magnetic anisotropy to stabilize skyrmions in thin films, surfaces, interfaces and bulk magnetic materials that break mirror symmetry.Recently there has been a surge of interest in skyrmions in chiral magnetic materials 1-3 , ranging from fundamental science to potential device applications. A skyrmion is a spin texture characterized by a topological invariant that, in metallic magnets, gives rise to the topological Hall effect 4,5 and may also have implications for nonFermi liquid behavior 6 . The ability to write and erase individual skyrmions 7 , along with their topological stability, small size, and low depinning current density 8 , paves the way for potential information storage and processing applications.Experiments have focussed primarily on skyrmions in non-centrosymmetric crystals with broken bulk inversion symmetry, e.g., metals like MnSi, FeGe and insulators like Cu 2 OSeO 3 . In these bulk materials, the skyrmion crystal (SkX) phase is stable only in a very limited region of the magnetic field (H), temperature (T ) phase diagram 9-13 . On the other hand, the skyrmion phase is found to be stable over a much wider region of (T, H) in thin films of the same materials 10,14-16 , even extending down to T = 0 in some cases 14,16 . (A class of two dimensional (2D) systems shows atomic-scale skyrmions 17 arising from competing local interactions, distinct from the spin-orbit induced chiral interactions that we focus on here.)A key question that we address is this paper is: How can we enhance the domain of stability of skyrmion spin textures? We are motivated in part by the thin film experiments, and also by the possibility of chiral magnetism in new 2D systems like oxide interfaces [18][19][20] . We show how the SkX become progressively more stable over ever larger regions in parameter space of field H and magnetic anisotropy A, as the effects of broken surface inversion dominate over those of broken bulk inversion. The key parameter responsible for this behavior is the ratio D ⊥ /D of the strength of the chiral magnetic interaction arising from broken bulk inversion (D ) to that arising from broken surface inversion (D ⊥ ); see Fig...

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New Type of Stable Particlelike States in Chiral Magnets

Cited by 220 publications

References 45 publications

Neutron study of in-plane skyrmions in MnSi thin films

Neutron study of in-plane skyrmions in MnSi thin films

Stability of skyrmion textures and the role of thermal fluctuations in cubic helimagnets: A new intermediate phase at low temperature

Skyrmions in chiral magnets with Rashba and Dresselhaus spin-orbit coupling

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