Pinning and hysteresis in the field dependent diameter evolution of skyrmions in Pt/Co/Ir superlattice stacks

Zeissler, Katharina; Mruczkiewicz, M.; Finizio, Simone; Raabe, Jörg; Shepley, Philippa M.; Садовников, А. В.; Никитов, С. А.; Fallon, Kayla; McFadzean, S.; McVitie, S.; Moore, T. A.; Burnell, Gavin; Marrows, C. H.

doi:10.1038/s41598-017-15262-3

Cited by 73 publications

(78 citation statements)

References 33 publications

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“…However, the symmetry in the preferential positions is not perfect, suggesting that local variations in material parameters also influence the preferential positions. In earlier works it was found that such local variations in material parameters were dominant in determining the equilibrium positions of skyrmions 17,18 , but our results clearly indicate that the shape of the structures is the dominant influence for the magnetic structures investigated here. Last, Fig.…”

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confidence: 45%

Controlling skyrmion bubble confinement by dipolar interactions

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Lichtenberg

Swagten

et al. 2019

Applied Physics Letters

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Large skyrmion bubbles in confined geometries of various sizes and shapes are investigated, typically in the range of several micrometers. Two fundamentally different cases are studied to address the role of dipole-dipole interactions: (I) when there is no magnetic material present outside the small geometries and (II) when the geometries are embedded in films with a uniform magnetization. It is found that the preferential position of the skyrmion bubbles can be controlled by the geometrical shape, which turns out to be a stronger influence than local variations in material parameters. In addition, independent switching of the direction of the magnetization outside the small geometries can be used to further manipulate these preferential positions, in particular with respect to the edges. We show by numerical calculations that the observed interactions between the skyrmion bubbles and structure edge including the overall positioning of the bubbles are fully controlled by dipole-dipole interactions. a) Electronic mail: t.lichtenberg@tue.nl 1 arXiv:1905.10304v1 [cond-mat.mes-hall] 24 May 2019Magnetic skyrmions are whirls in the magnetization in which neighbouring spins are rotated with respect to each other with a specific chirality. They cannot be removed by continuous deformation of the magnetization without creating a singularity, which provides a topological barrier that makes them robust against annihilation. They are less hindered by pinning sites or defects than magnetic domain walls (DWs), and their size can be in the order of nanometers. These properties make them suitable for data storage. For the envisioned skyrmion racetrack memory 1-3 , the skyrmions are required to be present in small geometrically confined structures, instead of infinite sheets of material. Therefore, the interaction between skyrmions and the edge of the magnetic structure is crucial. In fact, this interaction is necessary to prevent skyrmions from being expelled from the track, it can stabilize skyrmions in absence of an external magnetic field 4,5 , assist in their formation 6,7 , and by reducing the width of the track it could be possible to reduce the size of the skyrmion and hence to achieve larger data storage densities 8 .In the research field on skyrmions, usually a distinction is made between a 'compact skyrmion' and a 'skyrmion bubble'. These objects share many properties, but the latter has typically a much larger size and has a constant magnetization at its core 8 . Numerical and experimental work on compact skyrmion confinement show that there is indeed a repulsive interaction between skyrmions and sample edges that is a result of tilting of the magnetic moments at the edge, which is caused by the Dzyaloshinskii-Moriya interaction (DMI) 9,10 . For skyrmion bubbles, dipolar interactions are paramount in their stabilization, and because near the sample edge these stray fields will change, it is intuitively expected that the edges will influence the skyrmion bubbles via this mechanism. Though this has been realized before 1...

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confidence: 45%

Controlling skyrmion bubble confinement by dipolar interactions

Ummelen

Lichtenberg

Swagten

et al. 2019

Applied Physics Letters

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“…The skyrmion Hall angles below diameters of 150 nm do not follow the predicted trend of growing rapidly as the skyrmion diameter decreases. Skyrmion motion is known to be affected by the grain-to-grain variation in the magnetic properties of polycrystalline metallic films 24 . Modelling predicts that the skyrmion Hall angle approaches the pristine film value as the velocity increases 22,23 .…”

Section: Imaging Current-driven Skyrmion Motionmentioning

confidence: 99%

“…It has become more and more apparent that sputtered multilayer systems are prone to imperfections. While it is clear that nanoscale variations in the magnetic parameters of devices lead to skyrmion deformation and a wide range of stable diameters 23,24 , their influence on motion and the skyrmion Hall angle remains an active field of debate 20,22,23,[25][26][27] . On the one hand, skyrmion Hall angle deviations are attributed to dynamic deformation of the skyrmion during the motion 21 and on the other hand deviations are attributed to magnetic grains within the material 22,23,27 and defects 25,26 .…”

Section: Introductionmentioning

confidence: 99%

Diameter-independent skyrmion Hall angle observed in chiral magnetic multilayers

et al. 2020

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wordsMagnetic skyrmions are topologically non-trivial nanoscale objects. Their topology, which originates in their chiral domain wall winding, governs their unique response to a motion-inducing force. When subjected to an electrical current, the chiral winding of the spin texture leads to a deflection of the skyrmion trajectory, characterized by an angle with respect to the applied force direction. This skyrmion Hall angle was believed to be skyrmion diameter-dependent. In contrast, our experimental study finds that within the plastic flow regime the skyrmion Hall angle is diameter-independent. At an average velocity of 6 ± 1 m/s the average skyrmion Hall angle was measured to be 9° ± 2°. In fact, in the plastic flow regime, the skyrmion dynamics is dominated by the local energy landscape such as materials defects and the local magnetic configuration.

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“…The interfacial DM interaction has attracted much interest [5,8,9,[11][12][13][14][15] and has been investigated using different techniques [5,7,[15][16][17][18]. A commonly used method, particularly for ultrathin trilayer films with perpendicular magnetic anisotropy, is the expansion of reverse domains in the creep regime under in-plane bias fields, introduced by Je et al [7].…”

Section: Introductionmentioning

confidence: 99%

“…This method has been applied in a range of cases, sometimes giving results that fit well to the modified creep model [7,13,14], sometimes giving results that are more difficult to interpret [12,15,16] or that do not give the same value for the DM energy as other methods [16]. Where it fits well to experimental data and gives a clear result, the creep model can provide a value for the DM energy over a localized area (for example, close to a defect acting as a nucleation center) in which other phenomena are being observed, or provide a lower limit for a thin film [18].…”

Section: Introductionmentioning

confidence: 99%

Magnetic properties, domain-wall creep motion, and the Dzyaloshinskii-Moriya interaction in Pt/Co/Ir thin films

et al. 2018

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We study the magnetic properties of perpendicularly magnetized Pt/Co/Ir thin films and investigate the domain-wall creep method of determining the interfacial Dzyaloshinskii-Moriya (DM) interaction in ultrathin films. Measurements of the Co layer thickness dependence of saturation magnetization, perpendicular magnetic anisotropy, and symmetric and antisymmetric (i.e., DM) exchange energies in Pt/Co/Ir thin films have been made to determine the relationship between these properties. We discuss the measurement of the DM interaction by the expansion of a reverse domain in the domain-wall creep regime. We show how the creep parameters behave as a function of in-plane bias field and discuss the effects of domain-wall roughness on the measurement of the DM interaction by domain expansion. Whereas modifications to the creep law with DM field and in-plane bias fields have taken into account changes in the energy barrier scaling parameter α, we find that both α and the velocity scaling parameter v 0 change as a function of in-plane bias field.

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Pinning and hysteresis in the field dependent diameter evolution of skyrmions in Pt/Co/Ir superlattice stacks

Cited by 73 publications

References 33 publications

Controlling skyrmion bubble confinement by dipolar interactions

Controlling skyrmion bubble confinement by dipolar interactions

Diameter-independent skyrmion Hall angle observed in chiral magnetic multilayers

Magnetic properties, domain-wall creep motion, and the Dzyaloshinskii-Moriya interaction in Pt/Co/Ir thin films

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