Observation of magnetic skyrmions in unpatterned symmetric multilayers at room temperature and zero magnetic field

Brandão, J.; Dugato, Danian Alexandre; Seeger, R. L.; Denardin, Juliano C.; Mori, T. J. A.; Cezar, J. C.

doi:10.1038/s41598-019-40705-4

Cited by 50 publications

(54 citation statements)

References 43 publications

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“…Figures 5(a) showing skyrmions in magnetic materials with uniaxial magnetic anisotropy. [31][32][33] Each "worm" (band domain) and each spherical domain correspond to one Hall-effect quantum, and the formation of these domains is likely to involve branching from the middle of the relatively thick ribbons. 34 An excessive applied field leads to the disappearance of skyrmions in NiMnGa, and a nearly uniform magnetization distribution results, Fig.…”

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confidence: 99%

Comparative study of topological Hall effect and skyrmions in NiMnIn and NiMnGa

Zhang

Balamurugan

Ullah

et al. 2019

Applied Physics Letters

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A nonequilibrium rapid-quenching method has been used to fabricate NiMnIn and NiMnGa alloys that are chemically and morphologically similar but crystallographically and physically very different. NiMnGa crystallizes in a Ni 2 In-type hexagonal structure, whereas NiMnIn is a cubic Heusler alloy. Both alloys yield a topological Hall effect contribution corresponding to bubble-type skyrmion spin structures, but it occurs in much lower magnetic fields in NiMnIn as compared to NiMnGa. The effect is unrelated to net Dzyaloshinskii-Moriya interactions, which are absent in both alloys due to their inversion-symmetric crystal structures. Based on magnetic-force microscopy, we explain the difference between the two alloys by magnetocrystalline anisotropy and uniaxial and cubic anisotropies yielding full-fledged and reduced topological Hall effects, respectively. Since NiMnIn involves small magnetic fields (0.02-0.3 kOe) at and above room temperature, it is of potential interest in spin electronics.

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confidence: 99%

Comparative study of topological Hall effect and skyrmions in NiMnIn and NiMnGa

Zhang

Balamurugan

Ullah

et al. 2019

Applied Physics Letters

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“…We know that the challenge for using magnetic skyrmions in applications is to find room temperature-stabled skyrmions without external force. Recently, several experiments have demonstrated that ultrathin ferromagnetic/heavy metal multilayers are good structures that can host skyrmions at zero magnetic field and room temperature 42 – 44 , and its size and density also can be controlled by the shape and size of the nanostructure 44 . Our above results show an evidence that curvature is also a method to reduce the magnetic field to stabilize skyrmions.…”

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confidence: 99%

Nucleation and stability of skyrmions in three-dimensional chiral nanostructures

Liu

Cai

et al. 2020

Sci Rep

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We studied the magnetization evolution in three-dimensional chiral nanostructures, including nanotubes and circularly curved thin films, by micromagnetic simulations. We found that in a nanotube skyrmions can be formed by broken of the helical stripes on the left and right sides of the nanotube, and the formation of skyrmions doesn’t correspond to any abrupt change of topological number. Skyrmions can exist in a large range of magnetic field, and the thinner nanotube has a larger field range for skyrmion existence. The configuration of a skyrmion in nanotubes is different from the one in thin film. From the outer to the inner circular layer, the size of the skyrmion becomes larger, and the deformation becomes more obvious. In circularly curved magnetic films with fixed arc length, there are three kinds of hysteresis processes are found. For the curved films with a large radius, the magnetization evolution behavior is similar to the case in two-dimensional thin films. For the curved films with a small radius, the skyrmions are created by broken of the helical stripes on the left and right sides of the curved film. For the curved film with a medium radius, no skyrmion is formed in the hysteresis process.

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“…If all multiple intersections of each set curve occur at one quarter, but the central part has single intersections, we obtain double loops as inFigure 4. This result takes place at low temperatures (T ≤ 300[K]), see also[31].…”

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Ferromagnetic Hysteresis by Heisenberg Partition Function and Its Processing Methods in Nanoparticle Magnetization Modeling

Chychkalo¹,

Leble²

2021

Preprint

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The Heisenberg {\it ab initio} theory of magnetization is developed to apply for multilayer nanoparticles. The theory is based on distribution and partition functions modification with account the difference between exchange integral and closest neighbour numbers, that change the system of resulting transcendental equation for magnetization and its reversal to form either a paramagnetic type curve or hysteresis loops patterns. The equations are obtained within the Heisenberg partition function construction by Heitler diagonalization of energy matrix via irreducible representations of permutation symmetry group. A combination with the Gauss distribution gives the explicit expression for the partition function in the asymptotic limit] at large spin range in terms of transcendent function. The exchange integral, as a parameter of the equation of state (material equation) is evaluated from Curie temperature value by means of a formula derived within the presented theory. Methods of data processing from the simultaneous solution of the material equation system are proposed. The multi-valued function of hysteresis loop is found by combination of graphical approach and special procedure for elimination of mistaken peaks and prolapses of the patterns. The theory and computation methods are applied to spherical particles with separate surface layers consideration. The contribution of the surface layers, that are specified by number of closest neighbors and exchange integrals into overall magnetization, is studied for two-layer and three-layer models, that are discussed and compared graphically.

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Observation of magnetic skyrmions in unpatterned symmetric multilayers at room temperature and zero magnetic field

Cited by 50 publications

References 43 publications

Comparative study of topological Hall effect and skyrmions in NiMnIn and NiMnGa

Comparative study of topological Hall effect and skyrmions in NiMnIn and NiMnGa

Nucleation and stability of skyrmions in three-dimensional chiral nanostructures

Ferromagnetic Hysteresis by Heisenberg Partition Function and Its Processing Methods in Nanoparticle Magnetization Modeling

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