Generation and stability of dynamical skyrmions and droplet solitons

Statuto, Nahuel; Hernández, J. M.; Kent, Andrew D.; Maciá, Ferran

doi:10.1088/1361-6528/aac411

Cited by 10 publications

(8 citation statements)

References 44 publications

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“…2(c). 2,[22][23][24][25] Micromagnetic modeling has shown that the formation of topological droplets can be favored for certain initial magnetization states and current pulse rise times. 25 In these types of solitons, the boundary spins oscillate between Bloch and Néel configurations while maintaining a fixed topological charge.…”

Section: (B)mentioning

confidence: 99%

Magnetic droplet solitons

Maciá

Kent

2020

Journal of Applied Physics

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Magnetic droplet solitons are dynamical magnetic textures that form due to an attractive interaction between spin waves in thin films with perpendicular magnetic anisotropy. Spin currents and the spin torques associated with these currents enable their formation as they provide a means to excite non-equilibrium spin-wave populations and compensate their decay. Recent years have seen rapid advances in experiments that realize and study magnetic droplets. Important advances include the first direct x-ray images of droplets, determination of their threshold and sustaining currents, measurement of their generation and annihilation time, and evidence for drift instabilities, which can limit their lifetime. This perspective discusses these studies and contrasts these solitons to other types of spin-current excitations, such as spin-wave bullets, and static magnetic textures, including magnetic vortices and skyrmions. Magnetic droplet solitons can also serve as current controlled microwave frequency oscillators with potential applications in neuromorphic chips as nonlinear oscillators with memory.

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Section: (B)mentioning

confidence: 99%

Magnetic droplet solitons

Maciá

Kent

2020

Journal of Applied Physics

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“…Droplets have been experimentally created using the STT effect in electric nanocontacts to PMA films 9,10,24,25 . Here the Oersted fields also provide one more degree of complexity and could promote the existence of topological droplets [26][27][28] .…”

Section: Free Mange�c Layermentioning

confidence: 99%

Effects of the Zhang-Li Torque on Spin Torque nano Oscillators

Albert,

Macià,

Hernàndez

2020

Preprint

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Spin-torque nano-oscillators (STNO) are microwave auto-oscillators based on magnetic resonances having a nonlinear response with the oscillating amplitude, which provides them with a large frequency tunability including the possibility of mutual synchronization. The magnetization dynamics in STNO are induced by spin transfer torque (STT) from spin currents and can be detected by changes in electrical resistance due to giant magnetoresistance or tunneling magnetoresistance. The STT effect is usually treated as a damping-like term that reduces magnetic dissipation and promotes excitation of magnetic modes. However, an additional term, known as Zhang-Li term has an effect on magnetization gradients such as domain walls, and could have an effect on localized magnetic modes in STNO. Here we study the effect of Zhang-Li torques in magnetic excitations produced in STNO with a nanocontact geometry. Using micromagnetic simulations we find that Zhang-Li torque modify threshold currents of magnetic modes and their effective sizes. Additionally we show that effects can be controlled by changing the ratio between nanocontact size and layer thickness.

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“…This was mainly due to the large precession angle of the magnetic droplet mode [7,18,19]. However, all experimental work on magnetic droplets has, until now, focused on spin-valve (SV) structures [18,19,[21][22][23] and spin-hall nano-oscillators (SHNOs) [24,25]. The very low magnetoresistance (MR) (approximately 1%) in SVs and SHNOs limits power emission and any further use in STNO-based applications.…”

Section: Introductionmentioning

confidence: 99%

“…In contrast to our previous work on an SFL MTJ 29 , the magnetic droplets are successfully observed in a DFL MTJ here. To clarify the essential difference, we 6 perform the micromagnetic simulations 23,24 to further analyze the stability of magnetic droplets. Usually, the size of the droplet is determined by a combination of factors, such as the external magnetic field, the Zhang-Li torque induced by realistic lateral current spreading 22 , and the pinning field of the free layer.…”

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confidence: 99%

Observation of magnetic droplets in magnetic tunnel junctions

Shi

Cai

Jiang

et al. 2021

Sci. China Phys. Mech. Astron.

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Magnetic droplets, a class of highly nonlinear magnetodynamic solitons, can be nucleated and stabilized in nanocontact spin-torque nano-oscillators. Here we experimentally demonstrate magnetic droplets in magnetic tunnel junctions (MTJs). The droplet nucleation is accompanied by power enhancement compared with its ferromagnetic resonance modes. The nucleation and stabilization of droplets are ascribed to the double-CoFeB free-layer structure in the all-perpendicular MTJ, which provides a low Zhang-Li torque and a high pinning field. Our results enable better electrical sensitivity in fundamental studies of droplets and show that the droplets can be utilized in MTJ-based applications and materials science.

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Generation and stability of dynamical skyrmions and droplet solitons

Cited by 10 publications

References 44 publications

Magnetic droplet solitons

Magnetic droplet solitons

Effects of the Zhang-Li Torque on Spin Torque nano Oscillators

Observation of magnetic droplets in magnetic tunnel junctions

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