<i>B</i>–<i>T</i> phase diagram of Pd/Fe/Ir(111) computed with parallel tempering Monte Carlo

Böttcher, Marie; Heinze, Stefan; Егоров, С. А.; Sinova, Jairo; Dupé, Bertrand

doi:10.1088/1367-2630/aae282

Cited by 66 publications

(58 citation statements)

References 53 publications

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“…A recent theoretical study has revealed through atomistic simulations that thermal energy alone can lead to dynamical changes in the net skyrmion charge Q in Pd/Fe/Ir(111) ultrathin films . Here, we experimentally find a similar thermally driven increase in Q after injecting current pulses into Pt/CoFeB/MgO multilayers with ultralow‐pinning.…”

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confidence: 62%

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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confidence: 62%

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

et al. 2018

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“…We focus on the collapse of isolated skyrmions in the ferromagnetic background in Pd/Fe atomic bilayers on the (111) surfaces of Ir and Rh. The first system has been extensively studied experimentally [7,8,23,26,27] as well as theoretically [10,11,[28][29][30][31], while in the latter skyrmions have been recently predicted [32]. We find a pronounced response of the attempt frequency to the applied magnetic field close to the asymptotic divergence of the skyrmion size.…”

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confidence: 67%

Skyrmion lifetime in ultrathin films

et al. 2019

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We show that thermal stability of magnetic skyrmions can be strongly affected by entropic effects. The lifetimes of isolated skyrmions in atomic Pd/Fe bilayers on Ir(111) and on Rh(111) are calculated in the framework of harmonic transition state theory based on an atomistic spin model parametrized from density functional theory. Depending on the system the attempt frequency for skyrmion collapse can change by up to nine orders of magnitude with the strength of the applied magnetic field. We demonstrate that this effect is due to a drastic change of entropy with skyrmion radius which opens a novel route towards stabilizing sub-10 nm skyrmions at room temperature.

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“…Note that in Monte Carlo methods, the parallel tempering algorithm has proven to be an effective tool. [41][42][43] The usage of Python and a MPI package would enable one to quite easily reproduce this algorithm in a Python script using Spirit.…”

Section: B Monte Carlomentioning

confidence: 99%

Spirit : Multifunctional framework for atomistic spin simulations

et al. 2019

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The Spirit framework is designed for atomic scale spin simulations of magnetic systems of arbitrary geometry and magnetic structure, providing a graphical user interface with powerful visualizations and an easy to use scripting interface. An extended Heisenberg type spin-lattice Hamiltonian including competing exchange interactions between neighbors at arbitrary distance, higher-order exchange, Dzyaloshinskii-Moriya and dipole-dipole interactions is used to describe the energetics of a system of classical spins localised at atom positions. A variety of common simulations methods are implemented including Monte Carlo and various time evolution algorithms based on the Landau-Lifshitz-Gilbert equation of motion, which can be used to determine static ground state and metastable spin configurations, sample equilibrium and finite temperature thermodynamical properties of magnetic materials and nanostructures or calculate dynamical trajectories including spin torques induced by stochastic temperature or electric current. Methods for finding the mechanism and rate of thermally assisted transitions include the geodesic nudged elastic band method, which can be applied when both initial and final states are specified, and the minimum mode following method when only the initial state is given. The lifetime of magnetic states and rate of transitions can be evaluated within the harmonic approximation of transition-state theory. The framework offers performant CPU and GPU parallelizations. All methods are verified and applications to several systems, such as vortices, domain walls, skyrmions and bobbers are described.

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B–T phase diagram of Pd/Fe/Ir(111) computed with parallel tempering Monte Carlo

Cited by 66 publications

References 53 publications

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

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

Skyrmion lifetime in ultrathin films

Spirit : Multifunctional framework for atomistic spin simulations

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