Current-driven skyrmion depinning in magnetic granular films

Salimath, Akshaykumar; Abbout, Adel; Brataas, Arne; Manchon, Aurélien

doi:10.1103/physrevb.99.104416

Cited by 33 publications

(20 citation statements)

References 66 publications

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“…2. Although the critical current densities and skyrmion velocities for which the depinning and flow regimes are reached depend on the choice of disorder parameters [22,23,48], this approach constitutes a good qualitative description of the pinning effect on the current-driven skyrmion dynamics. Qualitatively, the micromagnetic simulations reveal that the disorderfree velocity and SkHA constitute upper bounds for the velocity and SkHA in disordered systems.…”

Section: Micromagnetic Simulationsmentioning

confidence: 99%

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

et al. 2019

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Magnetic skyrmions are chiral spin textures that hold great promise as nanoscale information carriers. Since their first observation at room temperature, progress has been made in their currentinduced manipulation, with fast motion reported in stray-field-coupled multilayers. However, the complex spin textures with hybrid chiralities and large power dissipation in these multilayers limit their practical implementation and the fundamental understanding of their dynamics. Here, we report on the current-driven motion of Néel skyrmions with diameters in the 100-nm range in an ultrathin Pt/Co/MgO trilayer. We find that these skyrmions can be driven at a speed of 100 m s −1 and exhibit a drive-dependent skyrmion Hall effect, which is accounted for by the effect of pinning. Our experiments are well substantiated by an analytical model of the skyrmion dynamics as well as by micromagnetic simulations including material inhomogeneities. This good agreement is enabled by the simple skyrmion spin structure in our system and a thorough characterization of its static and dynamical properties.

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Section: Micromagnetic Simulationsmentioning

confidence: 99%

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

et al. 2019

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“…Previous studies have shown how a threshold current arises due to confining pinning potentials 41,42 , defect scattering 43,44 , polycrystalline structures with crystallites of varying anisotropy axes orientation 45 , disorder originating from M S fluctuations using a granular structure 46 , as well as disorder in the DMI 7,8 and anisotropy constant 7,11 . Imperfections have also been shown to result in a change of the skyrmion Hall angle with skyrmion velocity due to sliding motion along grain boundaries 45 . Another mechanism which results in variation of the skyrmion Hall angle with velocity is due to the field-like SOT component in combination with breathing skyrmion modes 47,48 , or deformations and internal mode excitations 10 .…”

Section: Threshold Currentsmentioning

confidence: 99%

Effect of inter-layer spin diffusion on skyrmion motion in magnetic multilayers

Lepadatu

2019

Sci Rep

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It is well known that skyrmions can be driven using spin-orbit torques due to the spin-Hall effect. Here we show an additional contribution in multilayered stacks arises from vertical spin currents due to inter-layer diffusion of a spin accumulation generated at a skyrmion. This additional interfacial spin torque is similar in form to the in-plane spin transfer torque, but is significantly enhanced in ultra-thin films and acts in the opposite direction to the electron flow. The combination of this diffusive spin torque and the spin-orbit torque results in skyrmion motion which helps to explain the observation of small skyrmion Hall angles even with moderate magnetisation damping values. Further, the effect of material imperfections on threshold currents and skyrmion Hall angle is also investigated. Topographical surface roughness, as small as a single monolayer variation, is shown to be an important contributing factor in ultra-thin films, resulting in good agreement with experimental observations.

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“…In addition, their topological signatures make skyrmion detection in ferromagnets rather simple [35]. Besides these attractive features, ferromagnetic skyrmions also experience current-driven gyroscopic forces that can limit their scalability [31,32,36]. On the other hand, it was recently suggested that such gyroscopic forces could be exploited to enhance the mobility of a train of skyrmions in ferromagnetic nanotracks [37].…”

Section: Introductionmentioning

confidence: 99%

Controlling the deformation of antiferromagnetic skyrmions in the high-velocity regime

et al. 2020

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While antiferromagnetic skyrmions display appealing properties, their lateral expansion in the high-velocity regime hinders their potential for applications. In this work, we study the impact of spin Hall torque, spin transfer torque, and topological torque on the velocity-current relation of antiferromagnetic skyrmions with the aim of reducing this deformation. Using a combination of micromagnetic simulations and analytical derivations, we demonstrate that the lateral expansion of the antiferromagnetic skyrmion is reminiscent of the well-known Lorentz contraction identified in one-dimensional antiferromagnetic domain walls. We also show that in the flow regime the lateral expansion is accompanied by a progressive saturation of the skyrmion velocity when driven by spin Hall and topological torques. This saturation occurs at much smaller velocities when driven by the topological torque, while the lateral expansion is reduced, preventing the skyrmion size from diverging at large current densities. We extend this study toward synthetic antiferromagnets, where the weaker antiferromagnetic exchange leads to much larger lateral expansion at smaller current densities in all cases. This study suggests that a compromise must be made between skyrmion velocity and lateral expansion during the device design. In this respect, exploiting the topological torque could lead to better control of the skyrmion velocity in antiferromagnetic racetracks.

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Current-driven skyrmion depinning in magnetic granular films

Cited by 33 publications

References 66 publications

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

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

Effect of inter-layer spin diffusion on skyrmion motion in magnetic multilayers

Controlling the deformation of antiferromagnetic skyrmions in the high-velocity regime

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