Path to collapse for an isolated Néel skyrmion

Rohart, Stanislas; Miltat, J.; Thiaville, A.

doi:10.1103/physrevb.93.214412

Cited by 155 publications

(184 citation statements)

References 41 publications

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“…Taking µ = 3 Bohr magnetons and J = 10 meV, which are typical parameter values for two-dimensional magnetic systems based on transition metals [20,29], one obtains a pre-exponential factor of roughly 0.1 ns, a value which is actually often assumed in studies of thermally activated magnetic transitions [32,46,47].…”

Section: Resultsmentioning

confidence: 99%

“…Radial collapse is likely the only mechanism of skyrmion annihilation in extended two-dimensional systems described by the Hamiltonian in Eq. (2) [29,31,41] and the only one considered here.…”

Section: Methodsmentioning

confidence: 99%

“…The question then arises as to how general this relation between skyrmion size and skyrmion stability is and whether it is possible to design an optimal medium where magnetic skyrmions are small enough while being sufficiently stable at ambient conditions. Equilibrium properties of skyrmions such as size and shape have intensively been studied since the very discovery of magnetic skyrmions more than twenty years ago [2][3][4][22][23][24][25][26], but quantitative characterization of skyrmion stability has started being addressed rather recently [27][28][29][30][31][32][33][34][35][36][37][38]. Thermal stability can be quantified by calculating skyrmion lifetime using harmonic transition state theory for spins [39].…”

Section: Introductionmentioning

confidence: 99%

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Interplay between size and stability of magnetic skyrmions

Varentsova¹,

Potkina²,

Malottki³

et al. 2018

Nanosystems: Phys. Chem. Math.

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The relationship between the size and stability of isolated skyrmions in a magnetic monolayer is analyzed based on minimum energy path calculations and atomistic spin Hamiltonian. It is demonstrated that the energy barrier protecting the skyrmion from collapse to the ferromagnetic state is not uniquely defined by the skyrmion size, although these two properties as functions of relevant material parameters follow similar trends. Stability of nanoscale skyrmions can be enhanced by a concerted adjustment of material parameters. The proposed parameter transformation conserves the skyrmion size, but does not conserve the skyrmion shape which changes from an arrow-like pattern to a profile that resembles magnetic bubbles. This transformation of the skyrmion shape is accompanied by an increase in the collapse energy barrier and thus enhancement of skyrmion stability.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Interplay between size and stability of magnetic skyrmions

Varentsova¹,

Potkina²,

Malottki³

et al. 2018

Nanosystems: Phys. Chem. Math.

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show abstract

“…Since the dipolar coupling mainly acts as a shape anisotropy [31], it is possible to include its effect by reducing the anisotropy constant in the Hamiltonian [22,23]. This has been carefully examined in the current work for few-atom-thick films by directly calculating the dipolar interactions in the full neighborhood (i.e., all spin pairs).…”

Section: Modelmentioning

confidence: 99%

“…Very recently Refs. [22,23] reported detailed descriptions of the mechanisms for skyrmion collapse in a single atomic layer of magnetic material with interfacially induced DM interaction [24]. These restricted conditions can severely limit the use of skyrmions in practical applications because (a) creating large-area monolayers requires specialized preparation which will make commercial production hard to achieve and (b) isolated skyrmions in magnetic monolayers have only been observed at very low temperatures.…”

Section: Introductionmentioning

confidence: 99%

Paths to collapse for isolated skyrmions in few-monolayer ferromagnetic films

et al. 2017

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Magnetic skyrmions are topological spin configurations in materials with chiral Dzyaloshinskii-Moriya interaction (DMI), that are potentially useful for storing or processing information. To date, DMI has been found in few bulk materials, but can also be induced in atomically thin magnetic films in contact with surfaces with large spin-orbit interactions. Recent experiments have reported that isolated magnetic skyrmions can be stabilized even near room temperature in few-atom-thick magnetic layers sandwiched between materials that provide asymmetric spin-orbit coupling. Here we present the minimum-energy path analysis of three distinct mechanisms for the skyrmion collapse, based on ab initio input and the performed atomic-spin simulations. We focus on the stability of a skyrmion in three atomic layers of Co, either epitaxial on the Pt(111) surface or within a hybrid multilayer where DMI nontrivially varies per monolayer due to competition between different symmetry breaking from two sides of the Co film. In laterally finite systems, their constrained geometry causes poor thermal stability of the skyrmion toward collapse at the boundary, which we show to be resolved by designing the high-DMI structure within an extended film with lower or no DMI.

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Current‐Induced Skyrmion Generation through Morphological Thermal Transitions in Chiral Ferromagnetic Heterostructures

et al. 2018

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anisotropy (PMA). In ultrathin films, skyrmions can exhibit sub-nanometer scale size [8][9][10][11] and move in response to an applied current with velocities exceeding 100 m s -1 [5] in a controllable [12,13] and reliable [13] way. Therefore, they promise great technological utility for racetracktype memories, [14] logic gates, [15] probabilistic computing, [16] and neuromorphic devices, [17] for which they have to be readily created and manipulated. Homochiral skyrmions can be stabilized by the Dzyaloshinkii-Moriya interaction (DMI) [18,19] in materials with strong spin-orbit coupling and broken inversion symmetry. Since asymmetric multilayer stacks of a ferromagnet and a heavy metal [5][6][7] possess DMI and can also exhibit large current-induced spin-orbit torques that can provide an efficient means to create and manipulate skyrmions, [20][21][22] these systems are now a central focus of current research. Magnetic skyrmions can exist as isolated topological excitations, [23,24] or as ordered arrays (hexagonal lattice) comprising the magnetic ground state, [2,5] depending on material and Magnetic skyrmions promise breakthroughs in future memory and computing devices due to their inherent stability and small size. Their creation and current driven motion have been recently observed at room temperature, but the key mechanisms of their formation are not yet well-understood. Here it is shown that in heavy metal/ferromagnet heterostructures, pulsed currents can drive morphological transitions between labyrinth-like, stripe-like, and skyrmionic states. Using high-resolution X-ray microscopy, the spin texture evolution with temperature and magnetic field is imaged and it is demonstrated that with transient Joule heating, topological charges can be injected into the system, driving it across the stripe-skyrmion boundary. The observations are explained through atomistic spin dynamic and micromagnetic simulations that reveal a crossover to a global skyrmionic ground state above a threshold magnetic field, which is found to decrease with increasing temperature. It is demonstrated how by tuning the phase stability, one can reliably generate skyrmions by short current pulses and stabilize them at zero field, providing new means to create and manipulate spin textures in engineered chiral ferromagnets. Magnetic SkyrmionsThe ORCID identification number(s) for the author(s) of this article can be found under https://doi.

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Path to collapse for an isolated Néel skyrmion

Cited by 155 publications

References 41 publications

Interplay between size and stability of magnetic skyrmions

Interplay between size and stability of magnetic skyrmions

Paths to collapse for isolated skyrmions in few-monolayer ferromagnetic films

Current‐Induced Skyrmion Generation through Morphological Thermal Transitions in Chiral Ferromagnetic Heterostructures

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