Micromagnetic understanding of the skyrmion Hall angle current dependence in perpendicularly magnetized ferromagnets

Tomasello, Riccardo; Giordano, A.; Chiappini, Stefano; Zivieri, R.; Siracusano, Giulio; Puliafito, Vito; Medlej, Israa; Corte, Aurelio La; Azzerboni, B.; Carpentieri, Mario; Zeng, Zhongming; Finocchio, G.

doi:10.1103/physrevb.98.224418

Cited by 19 publications

(14 citation statements)

References 61 publications

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“…This is also consistent with LF measurements of the SkL in Cu 2 OSeO 3 [38]. We attribute the enhanced λ to skyrmion excitation modes with frequency ν (such as the low-frequency rotational and breathing modes in the SkL plane [39]) that soften (decreasing in frequency) as T increases towards T c [40,41]. As these modes cross through the frequency window where μSR is sensitive (around the Larmor resonance frequency ω 0 = γ μ B ext ) the relaxation rate increases.…”

supporting

confidence: 89%

Magnetism and Néel skyrmion dynamics in GaV4S8−ySey

Hicken

Holt

Franke

et al. 2020

Phys. Rev. Research

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We present an investigation of the influence of low levels of chemical substitution on the magnetic ground state and Néel skyrmion lattice (SkL) state in GaV 4 S 8-y Se y , where y = 0, 0.1, 7.9, and 8. Muon-spin spectroscopy (μSR) measurements on y = 0 and 0.1 materials reveal the magnetic ground state consists of microscopically coexisting incommensurate cycloidal and ferromagnetic environments, whereas chemical substitution leads to the growth of localized regions of increased spin density. μSR measurements of emergent low-frequency skyrmion dynamics show that the SkL exists under low levels of substitution at both ends of the series. Skyrmionic excitations persist to temperatures below the equilibrium SkL in substituted samples, suggesting the presence of skyrmion precursors over a wide range of temperatures.

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supporting

confidence: 89%

Magnetism and Néel skyrmion dynamics in GaV4S8−ySey

Hicken

Holt

Franke

et al. 2020

Phys. Rev. Research

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“…2). Furthermore, mechanisms involving a sizeable FL-SOT have been put forward to explain the drive-dependence of the SkHA of slightly deformed skyrmions [16] or breathing skyrmions [44]. However, our micromagnetic simulations including both SOTs with realistic relative amplitudes (up to C F L = C DL ) show no significant effect of the FL-SOT (see Sec.…”

Section: Micromagnetic Simulationsmentioning

confidence: 82%

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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“…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 . The field-like SOT in Eq.…”

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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Micromagnetic understanding of the skyrmion Hall angle current dependence in perpendicularly magnetized ferromagnets

Cited by 19 publications

References 61 publications

Magnetism and Néel skyrmion dynamics in GaV4S8−ySey

Magnetism and Néel skyrmion dynamics in GaV4S8−ySey

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

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