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Physics of Nanomagnets
Published in Klaus D. Sattler, 21st Century Nanoscience – A Handbook, 2020
Ralph Skomski, Balamurugan Balasubramanian, D. J. Sellmyer
A research area of renewed interest is magnetic skyrmions. By definition, skyrmions are solitonic solutions of nonlinear field equations originally used to describe nuclear matter [53]. Much of the interest in magnetic skyrmions comes from potential applications in date storage and processing, where miniaturization is a major consideration. An early example of magnetic skyrmions is magnetic bubbles, first described in 1967 [17]. Bubble skyrmions are stabilized by magnetic anisotropy and magnetostatic interactions, and DM interactions (Section 18.3.3) can be used to modify skyrmions, add functionality, and further improve stability [54]. The micro-magnetic description of skyrmions continues to be a challenge, aside from simple thin-film geometries [55,56], and often the DM vector is approximated by a scalar.
Magnetic Skyrmions on Discrete Lattices
Published in Evgeny Y. Tsymbal, Igor Žutić, Spintronics Handbook: Spin Transport and Magnetism, Second Edition, 2019
Elena Y. Vedmedenko, Roland Wiesendanger
Magnetic skyrmions have recently been in the focus of intense worldwide research activities, because they exhibit intriguing properties such as small lateral size and expected high stability due to their topological protection and the Dzyaloshinskii–Moriya (DM) interaction energy involved. A broad range of theoretical investigations on magnetic skyrmionic systems have been conducted in the framework of field theory, micromagnetics, or other theoretical approaches based on continuum media. There is also a considerable body of publications on magnetic skyrmions using discrete atomistic simulations or analytical calculations for atomistic models. While both theoretical approaches agree on the basic properties of the skyrmionic systems, there are certain subtleties that make one or another model more preferable for a certain problem. Particularly, the discrete treatment is very important for the interfacial skyrmionic systems in ultrathin magnetic films and for the confined geometries at the nanoscale.
Precessional Magnetization Dynamics and Spin Waves in 3D Ferromagnetic Nanostructures
Published in Gianluca Gubbiotti, Three-Dimensional Magnonics, 2019
Sucheta Mondal, Sourav Sahoo, Anjan Barman
Magnetic skyrmions are topologically protected magnetic solitons with a whirling spin texture [136]. This texture allows spins to align along all three dimensions. The topology is described by a winding number W: (
Skyrmions in blue phases of chiral liquid crystals
Published in Liquid Crystals, 2023
J. Pišljar, M. Marinčič, S. Ghosh, S. Turlapati, Rao Nandiraju, A. Nych, M. Škarabot, A. Mertelj, A. Petelin, A. Pusovnik, M. Ravnik, I. Muševič
Skyrmions were originally proposed to describe the stability of a nucleon as topological solitons of a pion field [33] by Tony Skyrme in 1962. In later years, it has been realised that these vortex-like field configurations could exist in other continuous field systems as well [34]. Skyrmions have been observed as 2D spin textures of a quantum Hall effect [35], as coreless vortex formations in spinor Bose–Einstein condensates [36] and as configurations of the velocity field in a superfluid phase [37]. Skyrmions in solid state materials are most prominent in chiral magnetic systems [38–40], where the often called ‘baby’ – skyrmions are tube-like localised swirls of magnetisation vector stabilised by the Dzyaloshinskii–Moriya interaction (DMI) between the magnetic spins [41,42]. Magnetic skyrmions are interesting for application in memory devices thanks to their fast responsiveness to external electrical current, small size and compactness and most importantly their energetic stability [43]. The latter is a consequence of topology of their structure, which cannot be disentangled into a homogeneous structure by any smooth transformation. A skyrmion can only be disentangled by applying an energetically costly discontinuity of the magnetisation field. In this sense, it is often said that skyrmions are topologically protected structures [44].
Theory of elastic interaction between axially symmetric 3D skyrmions in confined chiral nematic liquid crystals and in skyrmion bags
Published in Liquid Crystals, 2023
S. B. Chernyshuk, E. G. Rudnikov
Skyrmions were predicted and observed in quantum Hall systems [5–7]. Later, Bose–Einstein condensates with spin degrees of freedom were shown to accommodate Skyrmions [8–11]. As well, great attention has been paid to Skyrmions in noncentrosymmetric ferromagnets [12–18] with the presence of Dzyaloshinskii-Moriya spin-orbit interaction, such as MnSi [7,13,14] and [15,16]. Chiral magnetic skyrmions are now considered as promising objects for applications in magnetic data storage technologies and in the emerging spin transport electronics (spintronics), because local twisted magnetic structures coupled to electric or spin currents could be used to manipulate electrons and their spins [17,18]. Theoretical aspects of skyrmions in chiral magnets were investigated in [19–30].
Symmetry guide to chiroaxial transitions
Published in Phase Transitions, 2018
Recently, a lot of attention has been paid to materials that can host magnetic skyrmion lattices and individual soliton-like topological defects called skyrmions. The known phenomenological analysis [1,2] implies that the parent paramagnetic structures of materials hosting these peculiar magnetic textures should belong to certain crystal classes. Specifically, Bloch-skyrmion host parent structures belong to 3, 4, 6, 32, 422, and 622 crystal classes or their subclasses, while Néel-skyrmion host parent structures belong to 3m, 4mm, 6mm or their subclasses.