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Local dynamics of topological magnetic defects in the itinerant helimagnet FeGe.
Swiss Fed Inst Technol, Dept Phys, Otto Stern Weg 1, CH-8093 Zurich, Switzerland.
Swiss Fed Inst Technol, Dept Mat, Vladimir Prelog Weg 4, CH-8093 Zurich, Switzerland.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
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2016 (English)In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 7, 12430Article in journal (Refereed) Published
Abstract [en]

Chiral magnetic interactions induce complex spin textures including helical and conical spin spirals, as well as particle-like objects such as magnetic skyrmions and merons. These spin textures are the basis for innovative device paradigms and give rise to exotic topological phenomena, thus being of interest for both applied and fundamental sciences. Present key questions address the dynamics of the spin system and emergent topological defects. Here we analyse the micromagnetic dynamics in the helimagnetic phase of FeGe. By combining magnetic force microscopy, single-spin magnetometry and Landau-Lifschitz-Gilbert simulations we show that the nanoscale dynamics are governed by the depinning and subsequent motion of magnetic edge dislocations. The motion of these topologically stable objects triggers perturbations that can propagate over mesoscopic length scales. The observation of stochastic instabilities in the micromagnetic structure provides insight to the spatio-temporal dynamics of itinerant helimagnets and topological defects, and discloses open challenges regarding their technological usage.

Place, publisher, year, edition, pages
2016. Vol. 7, 12430
National Category
Condensed Matter Physics
Identifiers
URN: urn:nbn:se:uu:diva-291374DOI: 10.1038/ncomms12430ISI: 000381773100001PubMedID: 27535899OAI: oai:DiVA.org:uu-291374DiVA: diva2:925377
Funder
Swedish Research CouncileSSENCE - An eScience Collaboration
Available from: 2016-05-02 Created: 2016-05-02 Last updated: 2017-01-10Bibliographically approved
In thesis
1. Atomistic spin dynamics and relativistic effects in chiral nanomagnets
Open this publication in new window or tab >>Atomistic spin dynamics and relativistic effects in chiral nanomagnets
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis, studies based on magnetization dynamics on atomic length scales are presented for a number of magnetic systems, where Dzyaloshinskii-Moriya (DM) interaction is present. First-principle methods, based on density functional theory (DFT), have been used to study the pairwise magnetic interactions, such as Heisenberg exchange and DM interaction, which are the crucial parameters for the helimagnetic systems. The first part of this thesis concerns the theoretical background: basics of DFT, atomistic spin dynamics and magnetic skyrmions. The second part concerns the ground state and dynamical properties of helimagnets.

Magnetic interaction parameters have been calculated for heterostructures, such as Co/Ni/Co on heavy metal non-magnetic substrates. These parameters are strongly dependent on the material of the substrate. Furthermore, the magnetization dynamics of domain wall and skyrmion are studied and our results show that motion is influenced by the spin-Hall effect (SHE) which arises from the non-magnetic substrate. Similar studies of magnetic interaction parameters have been made for several half-Heusler compounds MnZSn (Z=Tc, Ru, Rh, Os, Ir and Pt) and the phase diagram of the MnPt0.99Ir0.01Sn alloy proves the existence of skyrmions in a wide range of temperature and external magnetic field. 

The manipulation of low-dimensional magnetic structures (skyrmions and solitons) with spin transfer torques have been investigated. The nucleation and annihilation processes of skyrmion, by the use of spin polarised current, are essential and the impact of different edges (antiferromagnetic, magnetically softer and stiffer) on both processes is studied. When the edge is magnetically softer, less current is required for skyrmion nucleation and annihilation. Furthermore, one-dimensional magnetic solitons are used to explore concepts of logical operations in a prototype majority gate device, since they are stable and can be easily created and manipulated by spin currents.

Lastly, edge dislocations in FeGe helimagnet have been studied. These dislocations described in terms of thermally driven dynamics by the use of atomistic spin dynamics approach and possibly explain some unusual jumps of the spiral wavelength observed by time-dependent experiments.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. 97 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1467
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-312462 (URN)978-91-554-9791-0 (ISBN)
Public defence
2017-02-27, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:00 (English)
Opponent
Supervisors
Available from: 2017-02-07 Created: 2017-01-10 Last updated: 2017-02-07

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