The Bloch point 3D topological charge induced by the magnetostatic interaction

Tejo, Felipe; Heredero, Rafael Hernández; Chubykalo‐Fesenko, O.; Guslienko, K. Yu.

doi:10.1038/s41598-021-01175-9

Cited by 21 publications

(23 citation statements)

References 41 publications

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“…we have calculated the value of the 2D topological charges for different cross-sections across the nanodot height. Although, in the literature different approaches have been proposed to describe the topology of three-dimensional magnetization configurations, such as the calculation of the Hopf index 31 – 33 or the integration of the gyrovector over a closed surface (which is quite relevant for the description of magnetization dynamics under the application of magnetic fields or currents 34 ), its proper notion is still a subject of debate. In our case, we have chosen to represent the 2D topological charge across the dot height as this allows direct comparison 23 with cylindrical thin nanodots.…”

Section: Resultsmentioning

confidence: 99%

3D quasi-skyrmions in thick cylindrical and dome-shape soft nanodots

Berganza

Fernández-Roldán

Jaafar

et al. 2022

Sci Rep

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Magnetic skyrmions are widely attracting researchers due to fascinating physics and novel applications related to their non-trivial topology. Néel skyrmions have been extensively investigated in magnetic systems with Dzyaloshinskii–Moriya interaction (DMI) and/or perpendicular magnetic anisotropy. Here, by means of micromagnetic simulations and analytical calculations, we show that 3D quasi-skyrmions of Néel type, with topological charge close to 1, can exist as metastable states in soft magnetic nanostructures with no DMI, such as in Permalloy thick cylindrical and dome-shaped nanodots. The key factor responsible for the stabilization of DMI-free is the interplay of the exchange and magnetostatic energies in the nanodots. The range of geometrical parameters where the skyrmions are found is wider in magnetic dome-shape nanodots than in their cylindrical counterparts. Our results open the door for a new research line related to the nucleation and stabilization of magnetic skyrmions in a broad class of nanostructured soft magnetic materials.

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Section: Resultsmentioning

confidence: 99%

3D quasi-skyrmions in thick cylindrical and dome-shape soft nanodots

Berganza

Fernández-Roldán

Jaafar

et al. 2022

Sci Rep

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“…In an ideal system the emergent field created by a monopole is simply B e ¼ Q 4πr 3 r with a Coulomb-like spherical configuration 47 but theoretical models suggest significant distortions in confined geometries 19,20 . In our case, a plot of B e Á dS; the density of emergent flux, on a 50 nm diameter spherical shell surrounding B6 (Fig.…”

Section: Bloch Points In the Magnetic Tomogrammentioning

confidence: 99%

“…However, direct experimental characterization of Bloch points has been elusive, since they are singular points with zero magnetization that must be observed by the surrounding 3D magnetization texture with the best possible resolution. This also implies that micromagnetic analysis of Bloch points is a challenging multiscale problem 18 particularly in the presence of magnetostatic confinement 19,20 .…”

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confidence: 99%

Bloch points and topological dipoles observed by X-ray vector magnetic tomography in a ferromagnetic microstructure

et al. 2023

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Bloch points are small 3D magnetic textures with unit topological charge that require the use of advanced vector imaging techniques for their direct experimental characterization. Here we show results from the reconstruction of the magnetization field $${{{{{\bf{m}}}}}}\left({{{{{\bf{r}}}}}}\right)$$ m r of an elongated permalloy microstructure by X-ray vector magnetic tomography. A central asymmetric Bloch domain wall is observed, decorated by Bloch points arranged in several dipoles and a triplet. The analysis of the $${{{{{\bf{m}}}}}}\left({{{{{\bf{r}}}}}}\right)$$ m r map in terms of topological concepts provides a quantitative description of the Bloch points as topological monopoles connected by bundles of emergent magnetic field lines carrying a fractional topological flux. It also reveals the topological constraints that determine chirality transitions of the central domain wall in the vicinity of Bloch points, independent of specific material properties. This approach could be readily extended to the study of magnetic microstructures in arbitrary remanent configurations.

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“…In this regard, if the complete magnetostatic interaction is considered for determining the BP profile, the twist angle of a BP hosted in a sphere is approximately 48 . This swirling effect originated from the magnetostatic energy leads to a non-zero 3D topological charge, which does not occur for radial BPs 49 .…”

Section: Introductionmentioning

confidence: 97%

Magnetostatic interaction between Bloch point nanospheres

Zambrano-Rabanal

Valderrama

Tejo

et al. 2023

Sci Rep

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Three-dimensional topological textures have become a topic of intense interest in recent years. This work uses analytical and numerical calculations to determine the magnetostatic field produced by a Bloch point (BP) singularity confined in a magnetic nanosphere. It is observed that BPs hosted in a nanosphere generate magnetic fields with quadrupolar nature. This finding is interesting because it shows the possibility of obtaining quadrupole magnetic fields with just one magnetic particle, unlike other propositions considering arrays of magnetic elements to generate this kind of field. The obtained magnetostatic field allows us to determine the interaction between two BPs as a function of the relative orientation of their polarities and the distance between them. It is shown that depending on the rotation of one BP related to the other, the magnetostatic interaction varies in strength and character, being attractive or repulsive. The obtained results reveal that the BP interaction has a complex behavior beyond topological charge-mediated interaction.

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The Bloch point 3D topological charge induced by the magnetostatic interaction

Cited by 21 publications

References 41 publications

3D quasi-skyrmions in thick cylindrical and dome-shape soft nanodots

3D quasi-skyrmions in thick cylindrical and dome-shape soft nanodots

Bloch points and topological dipoles observed by X-ray vector magnetic tomography in a ferromagnetic microstructure

Magnetostatic interaction between Bloch point nanospheres

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