Visualizing the strongly reshaped skyrmion Hall effect in multilayer wire devices

Tan, Ai-Girl; Ho, P.‐T.; Lourembam, James; Huang, Lisen; Tan, Hang Khume; Reichhardt, C.; Soumyanarayanan, Anjan

doi:10.1038/s41467-021-24114-8

Cited by 28 publications

(33 citation statements)

References 45 publications

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“…Pinning effects due to local changes in the material parameters compete with magnetic interactions and have a strong impact on the static and dynamic skyrmion properties 4 such as the shape and profile of skyrmions in the static ground state and during motion 23 , 24 . In particular also properties of skyrmion motion and dynamic effects such as the skyrmion Hall effect 24 , 25 are strongly affected by the distribution of pinning sites leading potentially to different skyrmion Hall angle dependences on the skyrmion size 26 , 27 . The local material inhomogeneities leading to local variations of the magnetic parameters define an energy landscape 23 which can qualitatively impact the dynamics depending on the details of the pinning 14 , 24 , 26 .…”

Section: Introductionmentioning

confidence: 99%

Skyrmion pinning energetics in thin film systems

et al. 2022

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A key issue for skyrmion dynamics and devices are pinning effects present in real systems. While posing a challenge for the realization of conventional skyrmionics devices, exploiting pinning effects can enable non-conventional computing approaches if the details of the pinning in real samples are quantified and understood. We demonstrate that using thermal skyrmion dynamics, we can characterize the pinning of a sample and we ascertain the spatially resolved energy landscape. To understand the mechanism of the pinning, we probe the strong skyrmion size and shape dependence of the pinning. Magnetic microscopy imaging demonstrates that in contrast to findings in previous investigations, for large skyrmions the pinning originates at the skyrmion boundary and not at its core. The boundary pinning is strongly influenced by the very complex pinning energy landscape that goes beyond the conventional effective rigid quasi-particle description. This gives rise to complex skyrmion shape distortions and allows for dynamic switching of pinning sites and flexible tuning of the pinning.

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Section: Introductionmentioning

confidence: 99%

Skyrmion pinning energetics in thin film systems

et al. 2022

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“…In a recent work the SkHA was investigated in Pt(3 nm)/Co(1.2 nm)/MgO(1.5 nm) multilayered tracks, also as a function of skyrmion diameter, and using skyrmion collections 31 . The experimental results are remarkably similar to those shown here, also showing small SkHA values, nearly-independent of skyrmion diameter, and small velocities under 10/ms.…”

Section: Results and Discussionmentioning

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 skyrmion–skyrmion interaction 28 , 29 , and constraint of skyrmion diameter when a layer is saturated by skyrmions 30 ; the extreme case being a skyrmion crystal. 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%

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

MacKinnon

Zeissler

Finizio

et al. 2022

Sci Rep

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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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“…Such a feature may lead to some unique dynamics compared to common particles. For example, a particlelike skyrmion driven by the spin current may move at an angle with respect to the driving force direction, which is called the skyrmion Hall effect [8,[40][41][42][43][44][45]. The skyrmion Hall effect originates from the topological Magnus force acting on the skyrmion, of which the direction is perpendicular to the skyrmion velocity, and the sign depends on the topological charge [8,[40][41][42][43][44][45].…”

Section: Introductionmentioning

confidence: 99%

“…For example, a particlelike skyrmion driven by the spin current may move at an angle with respect to the driving force direction, which is called the skyrmion Hall effect [8,[40][41][42][43][44][45]. The skyrmion Hall effect originates from the topological Magnus force acting on the skyrmion, of which the direction is perpendicular to the skyrmion velocity, and the sign depends on the topological charge [8,[40][41][42][43][44][45]. Therefore, a system containing massive interacting skyrmions driven by an external force may show very different dynamic properties compared to that of other particles or quasiparticles.…”

Section: Introductionmentioning

confidence: 99%

Structural transition of skyrmion quasiparticles under compression

Zhang,

Xia,

Liu

2022

Preprint

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The competition between external drives and interparticle interactions are important for the static and dynamic properties of topological quasiparticles in confined geometries. Here, we study the dynamics of particlelike skyrmions under a current-induced compression, where skyrmions are stabilized in a confined space and form a skyrmion solid. We find that a lattice structural transition of nanoscale skyrmions could be induced by the compression, which depends on the initial lattice configuration and the compression level. The compression effect in the skyrmion solid with strong skyrmion-skyrmion repulsion could produce a wave front showing an abrupt change of the skyrmion density, which may propagate through the skyrmion solid depending on the compression level. Besides, a chain of skyrmions on the surface of the compressed skyrmion solid could show a fast and stable motion along the surface as long as it remains within the driving region. Some skyrmions may collapse during the compression due to the destructive skyrmion-skyrmion collision, which mainly happens in the area around the skyrmion injection boundary between the driving and compressive regions. Our results are useful for understanding the compression physics of quasiparticles carrying nontrivial topology.

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Visualizing the strongly reshaped skyrmion Hall effect in multilayer wire devices

Cited by 28 publications

References 45 publications

Skyrmion pinning energetics in thin film systems

Skyrmion pinning energetics in thin film systems

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

Structural transition of skyrmion quasiparticles under compression

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