Edge-mediated skyrmion chain and its collective dynamics in a confined geometry

Du, Haifeng; Che, Renchao; Kong, Lingyao; Zhao, Xuebing; Jin, Chan; Wang, Chao; Yang, Jiyong; Ning, Wei; Li, Run-Wei; Chen, Jin; Chen, Xianhui; Zang, Jiadong; Zhang, Yuheng; Tian, Mingliang

doi:10.1038/ncomms9504

Cited by 230 publications

(239 citation statements)

References 26 publications

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“…Very recently, Du et al reported on real-space observation of a cascade of transitions in the magnetic structure of a FeGe wire [34]. Although this system stabilizes Bloch skyrmions, this work gives experimental corroboration of many of our findings, such as the existence of elongated skyrmions, the creation of skyrmions from edge states, and the enhanced stability of skyrmions in the confining geometry.…”

Section: Fig 1 (Color Online)supporting

confidence: 83%

Degeneracies and fluctuations of Néel skyrmions in confined geometries

et al. 2015

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The recent discovery of tunable Dzyaloshinskii-Moriya interactions in layered magnetic materials with perpendicular magnetic anisotropy makes them promising candidates for stabilization and manipulation of skyrmions at elevated temperatures. In this article, we use Monte Carlo simulations to investigate the robustness of skyrmions in these materials against thermal fluctuations and finite-size effects. We find that in confined geometries and at finite temperatures skyrmions are present in a large part of the phase diagram. Moreover, we find that the confined geometry favors the skyrmion over the spiral phase when compared to infinitely large systems. Upon tuning the magnetic field through the skyrmion phase, the system undergoes a cascade of transitions in the magnetic structure through states of different number of skyrmions, elongated and half-skyrmions, and spiral states. We consider how quantum and thermal fluctuations lift the degeneracies that occur at these transitions, and find that states with more skyrmions are typically favored by fluctuations over states with less skyrmions. Finally, we comment on electrical detection of the various phases through the topological and anomalous Hall effects.

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Section: Fig 1 (Color Online)supporting

confidence: 83%

Degeneracies and fluctuations of Néel skyrmions in confined geometries

et al. 2015

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“…For TEM measurements in a cross-sectional geometry, the Fresnel fringes generated by the film/substrate and film/cap interfaces wash out any magnetic contrast, unless the electron scattering potential of the chiral magnet is matched to the surrounding material, as was accomplished in Pt/FeGe/Pt nanostructures 24 . This is not the case for MnSi/Si interfaces where there is appreciable electron density differences, and neutron scattering is better suited to investigate the buried magnetic structures in this case.…”

Section: Methodsmentioning

confidence: 99%

“…The latter likely plays the dominant role in creating stable skyrmions in free-standing chiral magnetic nano-crystals [21][22][23][24] . Studies of the thickness dependence of the magnetic structure in wedgeshaped specimens reveals the influence of confinement on the skyrmions' stability 25,26 .…”

Section: Introductionmentioning

confidence: 99%

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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“…At H ≈ 1.96 kOe, the elongated skyrmions shrink into circles and assemble along the edge (Fig. 1F), indicating the attractive interaction among them (8,17).…”

Section: Significancementioning

confidence: 99%

“…1 G-J) (4,17). Finally, this triskyrmion cluster with triangular arrangement is formed in a wide interval of magnetic fields (1.96 kOe < H < 3.70 kOe), although the position of each individual skyrmion in the cluster can adjust correspondingly with the varied H (23).…”

Section: Significancementioning

confidence: 99%

Direct imaging of magnetic field-driven transitions of skyrmion cluster states in FeGe nanodisks

Zhao

Jin

Wang

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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142

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Magnetic skyrmion is a nanosized magnetic whirl with nontrivial topology, which is highly relevant for applications on future memory devices. To enable the applications, theoretical efforts have been made to understand the dynamics of individual skyrmions in magnetic nanostructures. However, directly imaging the evolution of highly geometrically confined individual skyrmions is challenging. Here, we report the magnetic field-driven dynamics of individual skyrmions in FeGe nanodisks with diameters on the order of several skyrmion sizes by using Lorentz transmission electron microscopy. In contrast to the conventional skyrmion lattice in bulk, a series of skyrmion cluster states with different geometrical configurations and the fielddriven cascading phase transitions are identified at temperatures far below the magnetic transition temperature. Furthermore, a dynamics, namely the intermittent jumps between the neighboring skyrmion cluster states, is found at elevated temperatures, at which the thermal energy competes with the energy barrier between the skyrmion cluster states.T he complex spin configurations in helimagnets have attracted considerable attention recently, with the topologically stable particle-like spin texture with a size down to the nanoscale, namely magnetic skyrmion, as the focus of interest (1). Magnetic skyrmion is characterized as a nanoscale topological particle producing unconventional spin electronic phenomena (2, 3) that holds great promise for future spintronic devices, including racetrack memory (4), magnetic random access memory, and magnetic sensors (1). Essentially, such schemes rely on the controllable formation and manipulation of individual skyrmions at nanostructured elements with various shapes such as disks, stripes, or wires (5-7). Investigation of skyrmions in confined geometries has therefore become one of the major topics in the field of skyrmion physics (5-10).Unlike ordinary magnetic vortices in microsized soft magnetic disks due to the minimization of the dipolar energy (11), the key ingredient of stabilizing skyrmions in helimagnets is the antisymmetry Dzyaloshinskii−Moriya (DM) interactions originating from the broken inversion symmetry (12). The competition of the DM coupling with ferromagnetic exchange interaction results in periodic helical ground state in helimagnets. Under the action of a magnetic field and temperature, these magnetic helices transfer into skyrmion crystal with triangular lattice configuration, and finally to the field-polarized ferromagnetic state. Notably, both ferromagnetic and DM couplings occur among the neighboring spins and belong to short-range interaction. Thus, it was demonstrated theoretically that skyrmions cluster states, characterized by certain arrangements of limited skyrmions, still persist even in submicrometer objects (8, 13). There, the longrange lattice form of skyrmions in 2D or bulk helimagnets is broken, but a short-ranged ordering with specific geometrical symmetries still remains, and the number of skyrmions in the cluster...

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Edge-mediated skyrmion chain and its collective dynamics in a confined geometry

Cited by 230 publications

References 26 publications

Degeneracies and fluctuations of Néel skyrmions in confined geometries

Degeneracies and fluctuations of Néel skyrmions in confined geometries

Neutron study of in-plane skyrmions in MnSi thin films

Direct imaging of magnetic field-driven transitions of skyrmion cluster states in FeGe nanodisks

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