Commensurability between Element Symmetry and the Number of Skyrmions Governing Skyrmion Diffusion in Confined Geometries

Song, Chi Young; Kerber, Nico; Rothörl, Jan; Ge, Yuqing; Raab, K; Seng, Boris; Brems, Maarten A.; Dittrich, Florian; Reeve, Robert M.; Wang, Jianbo; Liu, Qingfang; Virnau, Peter; Kläui, Mathias

doi:10.1002/adfm.202010739

Cited by 29 publications

(28 citation statements)

References 42 publications

(113 reference statements)

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“…[ 34–40 ] Hitherto, several experimental studies have been conducted to understand their behaviors. [ 35–40 ] For instance, Zhao et al. conducted a magnetic‐field‐driven cascading transition of skyrmion clusters and they also observed intermittent jumps between different skyrmion clusters; [ 38 ] recently, a thermally driven Brown diffusion of skyrmion clusters was reported in circular and triangular geometries.…”

Section: Introductionmentioning

confidence: 99%

Controlled Switching of the Number of Skyrmions in a Magnetic Nanodot by Electric Fields

et al. 2022

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through a skyrmion, its twisted spins endow these electrons with an emergent electromagnetic field, yielding a variety of unconventional magnetoelectronic phenomena, such as topological Hall effect [12] and ultralow current density for skyrmion motion. [23][24][25][26] These properties together with the nanoscale size and topological stability, make magnetic skyrmion promising potential for future highdensity, low-power-consuming magnetic memory devices. [1][2][3] Like many quasiparticles in condensed matter physics, magnetic skyrmion also has a particle-like characteristic. [1][2][3] Owing to this feature, multiple skyrmions can aggregate and dissipate in a defined geometry, which holds promise for applications beyond conventional binary memories, such as multi-level memories, [1,28,29] neuromorphic computing, [28][29][30] probabilistic computing, [31] and nano-oscillators. [32,33] In previous work, the experiment demonstrated an accumulation and dissipation of isolated skyrmions in micrometer-sized geometries using the spin-polarized pulse current. [30] However, since the skyrmion-skyrmion interaction between different Magnetic skyrmions are topological swirling spin configurations that hold promise for building future magnetic memories and logic circuits. Skyrmionic devices typically rely on the electrical manipulation of a single skyrmion, but controllably manipulating a group of skyrmions can lead to more compact and memory-efficient devices. Here, an electric-field-driven cascading transition of skyrmion clusters in a nanostructured ferromagnetic/ferroelectric multiferroic heterostructure is reported, which allows a continuous multilevel transition of the number of skyrmions in a one-by-one manner. Most notably, the transition is non-volatile and reversible, which is crucial for multi-bit memory applications. Combined experiments and theoretical simulations reveal that the switching of skyrmion clusters is induced by the strain-mediated modification of both the interfacial Dzyaloshinskii-Moriya interaction and effective uniaxial anisotropy. The results not only open up a new direction for constructing low-power-consuming, non-volatile, and multi-bit skyrmionic devices, but also offer valuable insights into the fundamental physics underlying the voltage manipulation of skyrmion clusters.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adma.202107908.

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Section: Introductionmentioning

confidence: 99%

Controlled Switching of the Number of Skyrmions in a Magnetic Nanodot by Electric Fields

et al. 2022

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“…The vast majority of these publications relies on the stability of the chiral magnetic objects. Recently, however, it has been shown theoretically [7] and experimentally [8,9] that skyrmions in various confined geometries can be structurally stable while performing a diffusional motion. Characteristics of this Brownian-like motion are of high importance for memory applications that use confined geometries such as race-tracks or as reservoirs.…”

Section: Introductionmentioning

confidence: 99%

Topological characterization of dynamic chiral magnetic textures using machine learning

Matthies,

Schäffer,

Posske

et al. 2022

Preprint

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Recently proposed spintronic devices use magnetic skyrmions as bits of information. The reliable detection of those chiral magnetic objects is an indispensable requirement. Yet, the high mobility of magnetic skyrmions leads to their stochastic motion at finite temperatures, which hinders the precise measurement of the topological numbers. Here, we demonstrate the successful training of artificial neural networks to reconstruct the skyrmion number in confined geometries from timeintegrated, dimensionally reduced data. Our results prove the possibility to recover the topological charge from a time-averaged measurement and hence smeared dynamic skyrmion ensemble, which is of immediate relevance to the interpretation of experimental results, skyrmion-based computing, and memory concepts.

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“…They have been observed in bulk materials and magnetic thin films at temperatures ranging from a few Kelvin to far above room temperature [1][2][3][4][5][6][7][8][9]. Skyrmions can be stabilized even without the application of an external field [10,11], can be manipulated efficiently with spin torques [9,12,13] and exhibit thermally activated dynamics [8,14,15]. This turns them into attractive candidates for applications in novel devices relying on skyrmion-based logic [15,16], Brownian computing [17,18] and racetrack memory [3,[19][20][21][22].…”

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confidence: 99%

“…Skyrmion interactions were analyzed in a Ta(5)/Co 20 Fe 60 B 20 (0.9)/Ta(0.08)/MgO(2)/Ta(5) (layer thickness in nm in parentheses) multilayer stack which had already been used in observation of skyrmion lattices in confined geometries [14]. The sample exhibits ferromagnetic properties with interfacial Dzyaloshinskii-Moriya interaction (DMI) and perpendicular magnetic anisotropy (PMA).…”

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confidence: 99%

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Constructing coarse-grained skyrmion potentials from experimental data with Iterative Boltzmann Inversion

Ge¹,

Rothörl²,

Brems³

et al. 2021

Preprint

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In an effort to understand skyrmion behavior on a coarse-grained level, skyrmions are often described as 2D quasi particles evolving according to the Thiele equation. Interaction potentials are the key missing parameters for predictive modeling of experiments. We apply the Iterative Boltzmann Inversion technique commonly used in soft matter simulations to construct potentials for skyrmion-skyrmion and skyrmion-magnetic material boundary interactions from a single experimental measurement without any prior assumptions of the potential form. We find that the two interactions are purely repulsive and can be described by an exponential function for experimentally relevant skyrmions. This captures the physics on experimental time and length scales that are of interest for most skyrmion applications and typically inaccessible to atomistic or micromagnetic simulations.

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Commensurability between Element Symmetry and the Number of Skyrmions Governing Skyrmion Diffusion in Confined Geometries

Cited by 29 publications

References 42 publications

Controlled Switching of the Number of Skyrmions in a Magnetic Nanodot by Electric Fields

Controlled Switching of the Number of Skyrmions in a Magnetic Nanodot by Electric Fields

Topological characterization of dynamic chiral magnetic textures using machine learning

Constructing coarse-grained skyrmion potentials from experimental data with Iterative Boltzmann Inversion

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