Controlled motion of skyrmions in a magnetic antidot lattice

Feilhauer, J.; Saha, Susmita; Tóbik, J.; Zelent, Mateusz; Heyderman, Laura J.; Mruczkiewicz, M.

doi:10.1103/physrevb.102.184425

Cited by 44 publications

(30 citation statements)

References 34 publications

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“…For example, in directional or symmetry locking, the particles preferentially move along certain symmetry directions of the pinning lattice even when the drive is not aligned with those directions, and as a result, for changing drive orientation a series of steps appear in the velocity versus driving angle curves [79][80][81][82][83][84] . Since the skyrmion Hall angle depends on the magnitude of the drive in systems with pinning, when individual skyrmions move over 2D periodic substrates, numerical studies have shown that the skyrmion motion locks to different substrate symmetry directions as the magnitude of the drive increases 48,85,86 . For a square array, such locking directions include 0 • and 45 • from a primary lattice vector.…”

Section: Introductionmentioning

confidence: 99%

Commensuration Effects on Skyrmion Hall Angle and Drag for Manipulation of Skyrmions on Two-Dimensional Periodic Substrates

Reichhardt,

Reichhardt

2022

Preprint

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We examine the dynamics of an individually driven skyrmion moving through a background lattice of skyrmions coupled to a 2D periodic substrate as we vary the ratio of the number of skyrmions to the number of pinning sites across commensurate and incommensurate conditions. As the skyrmion density increases, the skyrmion Hall angle is nonmonotonic, dropping to low or zero values in commensurate states and rising to an enhanced value in incommensurate states. Under commensuration, the driven skyrmion is channeled by a symmetry direction of the pinning array and exhibits an increased velocity. At fillings for which the skyrmion Hall angle is zero, the velocity has a narrow band noise signature, while for incommensurate fillings, the skyrmion motion is disordered and the velocity noise is broad band. Under commensurate conditions, multi-step depinning transitions appear and the skyrmion Hall angle is zero at low drives but becomes finite at higher drives, while at incommensurate fillings there is only a single depinning transition. As the gyrotropic component of the skyrmion dynamics, called the Magnus force, increases, peaks in the velocity that appear in commensurate regimes cross over to dips, and new types of directional locking effects can arise in which the skyrmion travels along other symmetry directions of the background lattice. At large Magnus forces, and particularly at commensurate fillings, the driven skyrmion can experience a velocity boost in which the skyrmion moves faster than the applied drive due to the alignment of the Magnus-induced velocity with the driving direction. In some cases, an increase of the Magnus force can produce regimes of enhanced pinning when the skyrmion is forced to move along a non-symmetry direction of the periodic pinning array. This is in contrast to systems with random pinning, where increasing the Magnus force generally reduces the pinning effect. We demonstrate these dynamics for both square and triangular substrates, and map out the different regimes as a function of filling fraction, pinning force, and the strength of the Magnus force in a series of dynamic phase diagrams.

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Section: Introductionmentioning

confidence: 99%

Commensuration Effects on Skyrmion Hall Angle and Drag for Manipulation of Skyrmions on Two-Dimensional Periodic Substrates

Reichhardt,

Reichhardt

2022

Preprint

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“…Moreover, the interaction of a skyrmion collection with the boundaries of a multilayered track was recently shown to result in a reshaped SkHE [31]. Driving individual skyrmions through a disordered landscape has been extensively studied under the effects of SOT from a HM layer [5,32], spin transfer torque (STT) in the FM layer [33], and more recently ISTT [24,25].…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, skyrmions interacting with neighbouring skyrmions have also been shown to repel each other due to the dipole-dipole and exchange interactions, thus leading to the possibility of skyrmionskyrmion interaction [28,29] and confinement of skyrmion diameter when a layer is saturated by skyrmions [30]; the extreme case being a skyrmion crystal. Driving individual skyrmions through a disordered landscape has been extensively studied under the effects of SOT from a HM layer [5,31], spin transfer torque (STT) in the FM layer [32], and more recently ISTT [24,25].…”

Section: Introductionmentioning

confidence: 99%

Collective skyrmion motion under the influence of an additional interfacial spin-transfer torque

MacKinnon¹,

Zeissler

Finizio

et al. 2022

Preprint

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Here we study the effect of an additional interfacial spin-transfer torque, as well as the well-established spin-orbit torque and bulk spin-transfer torque, on skyrmion collections – group of skyrmions dense enough that they are not isolated from one another – in ultrathin heavy metal / ferromagnetic multilayers, by comparing modelling with experimental results. Using a skyrmion collection with a range of skyrmion diameters and landscape disorder, we study the dependence of the skyrmion Hall angle on diameter and velocity, as well as the velocity as a function of diameter. We show that inclusion of the interfacial spin-transfer torque results in reduced skyrmion Hall angles, with values close to experimental results. We also show that for skyrmion collections the velocity is approximately independent of diameter, in marked contrast to the motion of isolated skyrmions, as the group of skyrmions move together at an average group velocity. Moreover, the calculated skyrmion velocities are comparable to those obtained in experiments when the interfacial spin-transfer torque is included. Our results thus show the significance of the interfacial spin-transfer torque in ultrathin magnetic multilayers, which helps to explain the low skyrmion Hall angles and velocities observed in experiment. We conclude that the interfacial spin-transfer torque should be considered in numerical modelling for reproduction of experimental results.

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“…R-IR transitions can also occur for particles moving over a periodic array of obstacles or a periodic substrate 21 . The dynamics of particles coupled to periodic substrates has been explored for superconducting vortices 26,[30][31][32] , magnetic skyrmions 33,34 , and colloidal systems [35][36][37][38][39][40] . A key aspect of systems with periodic substrates is that the dynamics depend strongly on the direction θ of drive relative to a substrate symmetry direction.…”

Section: Introductionmentioning

confidence: 99%

Reversible to Irreversible Transitions for Cyclically Driven Disks on Periodic Obstacle Arrays

Reichhardt,

Reichhardt

2022

Preprint

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We examine the collective dynamics of disks moving through a square array of obstacles under cyclic square wave driving. Below a critical density we find that system organizes into a reversible state in which the disks return to the same positions at the end of every drive cycle. Above this density, the dynamics are irreversible and the disks do not return to the same positions after each cycle. The critical density depends strongly on the angle θ between the driving direction and a symmetry axis of the obstacle array, with the highest critical densities appearing at commensurate angles such as θ = 0 • and θ = 45 • and the lowest critical densities falling at θ = arctan(0.618), the inverse of the golden ratio, where the flow is the most frustrated. As the density increases, the number of cycles required to reach a reversible state grows as a power law with an exponent near ν = 1.36, similar to what is found in periodically driven colloidal and superconducting vortex systems.

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Controlled motion of skyrmions in a magnetic antidot lattice

Cited by 44 publications

References 34 publications

Commensuration Effects on Skyrmion Hall Angle and Drag for Manipulation of Skyrmions on Two-Dimensional Periodic Substrates

Commensuration Effects on Skyrmion Hall Angle and Drag for Manipulation of Skyrmions on Two-Dimensional Periodic Substrates

Collective skyrmion motion under the influence of an additional interfacial spin-transfer torque

Reversible to Irreversible Transitions for Cyclically Driven Disks on Periodic Obstacle Arrays

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