Current-Driven Skyrmion Dynamics and Drive-Dependent Skyrmion Hall Effect in an Ultrathin Film

Juge, Roméo; Je, Soong-Geun; Chaves, Dayane de Souza; Buda-Prejbeanu, L. D.; Peña-Garcia, José; Nath, Jayshankar; Miron, Ioan Mihai; Rana, Kumari Gaurav; Aballe, Lucía; Foerster, Michael; Genuzio, Francesca; Menteş, Tevfik Onur; Locatelli, Andrea; Maccherozzi, Francesco; Dhesi, S. S.; Belmeguenai, M.; Roussigné, Y.; Auffret, S.; Pizzini, S.; Gaudin, Gilles; Vogel, Jan; Boulle, Olivier

doi:10.1103/physrevapplied.12.044007

Cited by 152 publications

(196 citation statements)

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“…It is worth noting that, the skyrmion Hall angle Θ in the this film without defects is independent of the current density, while that with quenched defects increases with the increasing current density, and approaches a constant value calculated in the absence of the pinning effect. This drive-dependent skyrmion Hall effect around the depinning phase transition has been experimentally observed [21,23,28,41]. In our results, different critical behaviors in the directions perpendicular and parallel to the driving current indicate a nonlinear relation between the skyrmion Hall angle Θ and the driving current u, because of the ratio…”

Section: Simulationssupporting

confidence: 76%

“…The pinning and depinning states, and the multiplication and annihilation of the current-driven skyrmions induced by quenched disorder have also been simulated based on the LLG equation [39,40]. Recently, experiments reveal that the skyrmions in disordered materials exhibit a drive-dependent skyrmion Hall effect just above the depinning threshold [21,23,28,41], and the simulation study suggests that the drive dependence is accounted for through the anisotropic behavior in the parallel and perpendicular directions of the skyrmion motion [42]. However, there is not any quantitative study of the anisotropic critical behavior on the depeinning phase transition.…”

Section: Introductionmentioning

confidence: 99%

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Anisotropic critical behavior of current-driven skyrmion dynamics in chiral magnets with disorder

et al. 2020

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The dynamic pinning effects are significant in manipulating skymions in chiral magnetic materials with quenched disorder. Through numerical simulations of the non-stationary current-driven dynamics of skyrmions with the Landau-Lifshitz-Gilbert equation, the critical current, static and dynamic critical exponents of the depenning phase transition are accurately determined for both adiabatic and non-adiabatic spin-transfer torques and with different strengths of disorder, based on the dynamic scaling behavior far from stationary. We find that the threshold current is insensitive to a small non-adiabatic coefficient of the spin-transfer torque, but dramatically reduced for a large one. The critical exponents indicate that the critical dynamic behavior is robust for different spin-transfer torques in the perpendicular component of the Hall motion, while exhibits a weak universality class in the direction of the driving current. The anisotropic behavior around the depinning phase transition provides a quantitative analysis of the drive-dependent skyrmion Hall effect in experiments. Further, the theoretical analysis using the Thiele's approach is presented, and the critical current and the static exponents support the simulation results.

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Section: Simulationssupporting

confidence: 76%

Section: Introductionmentioning

confidence: 99%

Anisotropic critical behavior of current-driven skyrmion dynamics in chiral magnets with disorder

et al. 2020

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“…The skyrmion Hall angle is constant in the absence of pinning or disorder, but in the presence of disorder it develops a dependence on drive or velocity, starting at a value of zero just at the depinning threshold and gradually increasing with increasing skyrmion velocity until saturating at high drives to a value close to that found in the clean limit [13][14][15][26][27][28][29][30][31] . Particle based 13,24,26,32,33 and continuum based 15,24,27,30 simulations show that the drive dependence of the skyrmion Hall angle is a result of the skyrmion-pin interactions.…”

Section: Introductionmentioning

confidence: 99%

Shear banding, intermittency, jamming, and dynamic phases for skyrmions in inhomogeneous pinning arrays

Reichhardt

2020

Phys. Rev. B

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We examine driven skyrmion dynamics in systems with inhomogeneous pinning where a strip of strong pinning coexists with a region containing no pinning. For driving parallel to the strip, we find that the initial skyrmion motion is confined to the unpinned region and the skyrmion Hall angle is zero. At larger drives, a transition occurs to a phase in which motion also appears within the pinned region, creating a shear band in the skyrmion velocity, while the skyrmion Hall angle is still zero. As the drive increases further, the flow becomes disordered and the skyrmion Hall angle increases with drive until saturating at the highest drives when the system transitions into a moving crystal phase. The different dynamic phases are associated with velocity and density gradients across the pinning boundaries. We map out the dynamic phases as a function of pinning strength, skyrmion density, and Magnus force strength, and correlate the phase boundaries with features in the velocity-force curves and changes in the local and global ordering of the skyrmion structure. For large Magnus forces, the shear banding instability is replaced by large scale intermittent flow in the pinned region accompanied by simultaneous motion perpendicular to the direction of the drive, which appears as oscillations in the transport curves. We also examine the case of a drive applied perpendicular to the strip, where we find a jamming effect in which the skyrmion flow is blocked by skyrmion-skyrmion interactions until the drive is large enough to induce plastic flow. arXiv:1911.06719v1 [cond-mat.mes-hall]

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“…In principle, skyrmion Hall angles of close to θ sk = 90 • are possible in certain systems. Experimental measurements of θ sk give values ranging from just a few degrees up to θ sk = 55 • [61][62][63][64][65]. These experiments are generally performed on larger skyrmions that can be observed directly, but much larger skyrmion Hall angles could be present in systems with smaller skyrmions.…”

mentioning

confidence: 99%

“…The skyrmion Hall angle is known to have a strong drive dependence in the presence of pinning. At low drives, the skyrmion Hall angle is small or zero, but θ sk increases with increasing drive before saturating at a value close to the pin-free limiting value for high drives [61][62][63][64][65][66][67][68][69][70]. This drive dependence can arise due to a side jump or swirling motion of the skyrmions that occurs when they interact with pinning sites, where faster moving skyrmions undergo a smaller side jump [71,72].…”

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confidence: 99%

Skyrmion dynamics and topological sorting on periodic obstacle arrays

2020

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We examine skyrmions under a dc drive interacting with a square array of obstacles for varied obstacle size and damping. When the drive is applied in a fixed direction, we find that the skyrmions are initially guided in the drive direction but also move transverse to the drive due to the Magnus force. The skyrmion Hall angle, which indicates the difference between the skyrmion direction of motion and the drive direction, increases with drive in a series of quantized steps as a result of the locking of the skyrmion motion to specific symmetry directions of the obstacle array. On these steps, the skyrmions collide with an integer number of obstacles to create a periodic motion. The transitions between the different locking steps are associated with jumps or dips in the velocity-force curves. In some regimes, the skyrmion Hall angle is actually higher than the intrinsic skyrmion Hall angle that would appear in the absence of obstacles. In the limit of zero damping, the skyrmion Hall angle is 90 • , and we find that it decreases as the damping increases. For multiple interacting skyrmion species in the collective regime, we find jammed behavior at low drives where the different skyrmion species are strongly coupled and move in the same direction. As the drive increases, the species decouple and each can lock to a different symmetry direction of the obstacle lattice, making it possible to perform topological sorting in analogy to the particle sorting methods used to fractionate different species of colloidal particles moving over two-dimensional obstacle arrays. © 2020 The Author(s). Published by IOP Publishing Ltd on behalf of the Institute of Physics and Deutsche Physikalische GesellschaftNew J. Phys. 22 (2020) 053025 N P Vizarim et alfrequency of the oscillations generated by the motion of the particle over the periodic substrate locks or comes into resonance with the ac drive frequency and its higher harmonics for a fixed range of drive intervals, producing steps in the velocity-force curves of the type found in Josephson junctions (which are known as Shapiro steps) [15,16], incommensurate sliding charge density waves [17], driven Frenkel-Kontorova systems [18], vortices in type-II superconductors moving over a periodic pinning substrate [19][20][21], and colloidal particles driven over periodic substrates [22,23]. In the case of the directional locking, there is no ac driving; however, two frequencies are still present, where one is associated with motion in the direction parallel to the drive and the other is associated with motion in the direction perpendicular to the drive. Directional locking can also arise in a system with a quasiperiodic substrate, where there are five or seven symmetry locking directions [24,25]. The locking can be harnessed for applications such as the sorting of different species of particles which have different sizes, charges, or damping, where a spatial separation of the species is achieved over time when one species locks to one angle while the other species locks to a different angl...

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Current-Driven Skyrmion Dynamics and Drive-Dependent Skyrmion Hall Effect in an Ultrathin Film

Cited by 152 publications

References 50 publications

Anisotropic critical behavior of current-driven skyrmion dynamics in chiral magnets with disorder

Anisotropic critical behavior of current-driven skyrmion dynamics in chiral magnets with disorder

Shear banding, intermittency, jamming, and dynamic phases for skyrmions in inhomogeneous pinning arrays

Skyrmion dynamics and topological sorting on periodic obstacle arrays

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