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Meron-antimeron Crystals with Spin Scalar Chiral Stripes

Jeudi 2 juillet 2015 14:00 - Duree : 1 heure
Lieu : ESRF, Salle de réunion 401, 4ème, Science Building (SB)

Orateur : Ryo OZAWA (Motone Group, Department of Applied Physics, University of Tokyo)

Skyrmion, a topologically-nontrivial magnetic structure with a noncoplanar spin configuration, has been extensively studied not only for the intriguing transport phenomena but also potential applications to electronic devices. The spin-orbit coupling plays an important role in stabilizing the noncoplanar spin textures and also in determining the size of skyrmions through the competition between the Dzyaloshinskii-Moriya interaction and the exchange interaction. As the spin-orbit coupling is an intrinsic parameter in each material, it is rather difficult to control the stability of skyrmions and to manipulate their sizes. For more variety and flexibility, it is desired to explore another class of nontrivial spin textures arising from different origins.

In this study, we propose a new mechanism for stabilizing the topologically-nontrivial magnetic order, in which the size of noncoplanar spin texture is flexibly varied. Instead of the spin-orbit coupling, we utilize the instability originating in the Fermi surface structure, which exists ubiquitously in itinerant electron systems. In this mechanism, the ordering vector is determined by the size and shape of the Fermi surface. We demonstrate this in simple spin-charge coupled systems, a family of square-lattice Kondo lattice models. Performing an efficient numerical simulation based on the Langevin dynamics, we find that a meron-antimeron crystal with spin scalar chiral stripes can have lower energy than the helical order that is inferred from the Ruderman-Kittel-Kasuya-Yosida interaction. We also investigate the stabilizing mechanism by the variational calculation, the truncation of the spin scattering processes, and the perturbation theory in terms of the spin-charge coupling and the degree of noncoplanarity. Our results show that the formation of meron-antimeron crystals is a dominant instability in the spin-charge coupled systems in a wide range of electron filling fractions.

Contact : taffut@ill.fr

Discipline évènement : (Physique)
Entité organisatrice : (ILL)
Nature évènement : (Séminaire)
Site de l'évènement : Polygone scientifique

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