Skyrmion relaxation dynamics in the presence of quenched disorder

Brown, Barton L.; Täuber, Uwe C.; Pleimling, Michel

doi:10.1103/physrevb.100.024410

Cited by 33 publications

(32 citation statements)

References 44 publications

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“…It should also be noted that the simulations employ a Langevin dynamics thermostat with a time step of 10 −3 and could be further improved by including additional specific terms to account for gyrotropic dynamics. [ 33–35 ] It is not expected that the current static equilibrium results are affected because such terms do not contribute to the energy of the system and thus do not break detailed balance. [ 35 ] However, to analyze the dynamics of the system evolution in the future, such terms need to be considered.…”

Section: Methodsmentioning

confidence: 99%

Skyrmion Lattice Phases in Thin Film Multilayer

Zázvorka

Dittrich

et al. 2020

Adv Funct Materials

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Phases of matter are ubiquitous with everyday examples including solids and liquids. In reduced dimensions, particular phases, such as the 2D hexatic phase and corresponding phase transitions occur. A particularly exciting example of 2D ordered systems are skyrmion lattices, where in contrast to previously studied 2D colloid systems, the skyrmion size and density can be tuned by temperature and magnetic fields. This allows for the system to be driven from a liquid phase to the onset of a hexatic phase as deduced from the analysis of the hexagonal order. Using coarse-grained molecular dynamics simulations of soft disks, the skyrmion interaction potentials are determined, and it is found that the simulations are able to reproduce the phase behavior. This shows that not only the static behavior of skyrmions is qualitatively well described in terms of a simple 2D model system but skyrmion lattices are versatile and tunable 2D model systems that allow for studying phases and phase transitions in reduced dimensions.

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Section: Methodsmentioning

confidence: 99%

Skyrmion Lattice Phases in Thin Film Multilayer

Zázvorka

Dittrich

et al. 2020

Adv Funct Materials

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“…In tandem to the few available experiments, scarce ab-initio simulations addressed the case of point-defects 34 , 36 , 39 , 40 while several phenomenological-based studies were dedicated to various defects assuming local changes in the magnetic properties of the material 3 , 28 , 29 , 33 , 35 , 41 – 48 . Yet, the energy-landscape impacting skyrmions as induced by complex defects remains weakly explored.…”

Section: Introductionmentioning

confidence: 99%

Sub-nanoscale atom-by-atom crafting of skyrmion-defect interaction profiles

Arjana

Fernandes

Chico

et al. 2020

Sci Rep

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Magnetic skyrmions are prime candidates as information carriers for spintronic devices due to their topological nature and nanometric size. However, unavoidable inhomogeneities inherent to any material leads to pinning or repulsion of skyrmions that, in analogy to biology concepts, define the phenotype of the skyrmion-defect interaction, generating complexity in their motion and challenging their application as future bits of information. Here, we demonstrate that atomby-atom manufacturing of multi-atomic defects, being antiferromagnetic or ferromagnetic, permits the breeding of their energy profiles, for which we build schematically a Punnet-square. As established from first-principles for skyrmions generated in PdFe bilayer on Ir(111) surface, the resulting interaction phenotype is rich. it can be opposite to the original one and eventually be of dual pinning-repulsive nature yielding energy landscapes hosting multi-domains. this is dictated by the stacking site, geometry, size and chemical nature of the adsorbed defects, which control the involved magnetic interactions. this work provides new insights towards the development of disruptive device architectures incorporating defects into their design aiming to control and guide skyrmions. Magnetic skyrmions 1,2 , i.e. non-collinear spin textures with particle-like properties, are promising future magnetic bits for future data storage technologies based on topological concepts 3-11. Of great technological relevance are skyrmions in thin films and magnetic multilayers 12-22 , which can be stabilized as a result of the competition among the Heisenberg exchange interaction (HEI), Dzyaloshinskii-Moriya interaction (DMI) 23,24 and the perpendicular magnetic anisotropy. The low spin polarized current thresholds required to manipulate skyrmions compared to typical ferromagnetic domain walls 3,25 along with their high mobility, high stability and small sizes make them ideal for achieving efficient and functional devices. However, defects that are ineluctable in any device and materials are often seen as inhibitors for applications. The dynamical behavior of the skyrmion motion as function of applied currents hinges on the presence of defects, which define the three motion regimes: pinning, creep-and steady-flow-motion as demonstrated experimentally in ultrathin heavy metal/ferromagnetic bilayers and multilayers 15,26,27. Considerable effort has been performed to explore the dynamics pertaining to current-induced skyrmion motion 3,4,15,28-32 , with a particular attention to the role of defects 33-36. In particular, simulations using realistic parameters extracted from ab-initio showed that by controlling the mutual distance of the pinning defects, one may engineer a double track to guide the skyrmion motion and enhance its velocity 36. Atomic-scale imaging based on scanning tunneling microscopy demonstrated that skyrmions in PdFe bilayer on Ir(111) are inert to the presence of a single Co adatom, in accordance to recent ab-initio simulations 34 , but react to the presence...

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“…Grains, together with point defects, can be considered as pinning sites, and have been shown to play an important role in the skyrmion dynamics [152,153,154]. Furthermore, by assuming skyrmions as rigid particles, molecular dynamics (MD) simulations have demonstrated the effect of point defects [155] on pinning and depinning [156,157], as well as altering skyrmion behavior under driving currents [151,158,159]. Theoretical and numerical studies of single skyrmions do not account for the possible interactions between skyrmions.…”

Section: Thermally-induced Motion Of Dense Skyrmion Arraysmentioning

confidence: 99%

Voltage control of skyrmions: Creation, annihilation, and zero-magnetic field stabilization

Zhou

Mansell

Dijken

2021

Applied Physics Letters

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Voltage manipulation of skyrmions is a promising path toward low-energy spintronic devices. Here, voltage effects on skyrmions in a GdOx/Gd/Co/Pt heterostructure are observed experimentally. The results show that the skyrmion density can be both enhanced and depleted by the application of an electric field, along with the ability, at certain magnetic fields to completely switch the skyrmion state on and off. Further, a zero magnetic field skyrmion state can be stabilized at a negative bias voltage using a defined voltage and magnetic field sequence. The voltage effects measured here occur on a few-second timescale, suggesting an origin in voltage-controlled magnetic anisotropy rather than ionic effects. By investigating the skyrmion nucleation rate as a function of temperature, we extract the energy barrier to skyrmion nucleation in our sample. Further, micromagnetic simulations are used to explore the effect of changing the anisotropy and Dzyaloshinskii–Moriya interaction on skyrmion density. Our work demonstrates the control of skyrmions by voltages, showing functionalities desirable for commercial devices.

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Skyrmion relaxation dynamics in the presence of quenched disorder

Cited by 33 publications

References 44 publications

Skyrmion Lattice Phases in Thin Film Multilayer

Skyrmion Lattice Phases in Thin Film Multilayer

Sub-nanoscale atom-by-atom crafting of skyrmion-defect interaction profiles

Voltage control of skyrmions: Creation, annihilation, and zero-magnetic field stabilization

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