Interplay between bulk and edge-bound topological defects in a square micromagnet

Slöetjes, Samuel Dingeman; Digernes, Einar; Olsen, Fredrik Kjemperud; Chopdekar, Rajesh V.; Retterer, Scott T.; Folven, Erik; Grepstad, J. K.

doi:10.1063/1.5010166

Cited by 4 publications

(1 citation statement)

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“…1(a). We have previously demonstrated [11] that excitation with an external magnetic field oriented at 45 • with the edges leads to a vortex core displacement along the square diagonal [Fig. 1(b)], followed by creation of edge topological defects with a fractional winding number [12] upon increasing the applied field, cf.…”

Section: Introductionmentioning

confidence: 99%

Exchange explosions of topological edge defects in a square micromagnet

2020

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The magnetodynamic properties of a square thin-film micromagnet (2 μm × 2 μm × 16 nm) with a fluxclosure magnetic ground state were investigated by micromagnetic simulations. The system was excited with an applied magnetic field, displacing the vortex core sufficiently far from its equilibrium position to result in a nonlinear relaxation upon removal of the field. We find that creation of edge topological defects leads to exchange explosions and periodic emission of short-wavelength spin waves emanating from these defects. The exchange explosions of the edge topological defects are investigated and explained in terms of vortex/antivortex creation and the formation of a Bloch point. This finding could prove useful to the development of nanoscale devices for periodic generation of high-frequency microwave radiation.

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Section: Introductionmentioning

confidence: 99%

Exchange explosions of topological edge defects in a square micromagnet

2020

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General Micromagnetic Theory and Applications

Kronmüller

2019

Materials Science and Technology

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The objective of this contribution is to review the principles of the continuum theory of micromagnetism and to show its applications to the main static and dynamic problems of ferromagnetic materials. Micromagnetism as a continuum theory closes the gap between quantum theory, dealing with atomic scales, and the Maxwell theory, dealing with macroscopic dimensions. Micromagnetism therefore corresponds to the tool to deal with nano‐ and microscales. Micromagnetism has become an indispensible theory for a fundamental understanding of magnetic domain configurations, magnetization processes, and the interaction between magnetization and microstructures. After Landau–Lifshitz's wall calculations in 1935 and Brown's publication of the so‐called Brown's micromagnetic equations in 1940/41, micromagnetism became the standard method to analyze the basic magnetic properties of ferromagnetic materials in the range of nano‐ and microscales. The following review gives a brief presentation of the different energy terms involved in the magnetic Gibbs free energy and a derivation of the micromagnetic equilibrium conditions and of the effective field. Some characteristic applications illustrate the effectiveness of micromagnetism in the case of domain walls, nucleation problems, interaction with microstructures, domain patterns, and the dynamics of magnetization processes. This contribution also gives a definition of the different exchange lengths related to dipolar fields, magnetocrystalline anisotropy energy, magnetostatic energy of external fields, and the magnetoelastic coupling energy. Whereas only a few cases exist where analytical solutions of the highly nonlinear micromagnetic equations are available, the progress in computational micromagnetism allowed the numerical solution of many open problems treated in the contributions by Miltat et al., Schrefl et al., and D. Goll in the Handbook of Magnetism and Advanced Magnetic Materials ed. by Kronmüller and Parkin Kronmüller and Parkin (2007).

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