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Aspects of Complex Magnetism: Vortex Phases, Skyrmion Dynamics, and Chaotic Nano-Oscillators

Wolba, Benjamin Berthold

Abstract (englisch):

Project I Vortex Phase in Spiral Antiferromagnets
Spiral antiferromagnets are characterized by a Dzyaloshinskii-Moriya interaction that stabilizes spatially modulated phases of the staggered order parameter. In the framework of a Ginzburg-Landau theory, it is shown that a magnetic field leads to the formation of a topological phase constituting a square lattice of vortices and antivortices. An orthogonal alignment of the antiferromagnetic staggered order parameter with an external magnetic field is energetically favorable since both sublattices of a spiral antiferromagnet cannot minimize their Zeeman energy simultaneously, and energy can be gained from spin canting. This spin-flop mechanism has the same effect as easy-plane anisotropy, which leads the vortices to form topological defects with vanishing core. Thus, the vortex phase is only stable close to the Néel temperature.
At lower temperatures, the square-lattice vortex phase undergoes spontaneous symme- try breaking into a rectangular phase. We investigate the stability of this rectangular phase with respect to mixed DMI and in-plane magnetic fields. Since any modulated magnetic texture induces a ferroelectric polarization, the vortices of both the vortex and the rectangular phase carry an electrical charge which makes them amenable to the ma- nipulation with in-plane electric fields. ... mehr

Volltext §
DOI: 10.5445/IR/1000140854
Veröffentlicht am 10.12.2021
Cover der Publikation
Zugehörige Institution(en) am KIT Institut für Theoretische Festkörperphysik (TFP)
Publikationstyp Hochschulschrift
Publikationsdatum 10.12.2021
Sprache Englisch
Identifikator KITopen-ID: 1000140854
Verlag Karlsruher Institut für Technologie (KIT)
Umfang v, 204 S.
Art der Arbeit Dissertation
Fakultät Fakultät für Physik (PHYSIK)
Institut Institut für Theoretische Festkörperphysik (TFP)
Prüfungsdatum 29.10.2021
Referent/Betreuer Garst, M.
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