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Communication Dans Un Congrès Année : 2023

Contribution of the antiferromagnetic coupling on the skyrmion dynamics in ferrimagnets and synthetic antiferromagnets

Stanislas Rohart
Sujit Panigrahy
Léo Berges
Joao Sampaio
Alexandra Mougin

Résumé

Skyrmions are magnetic solitons for which thetopology plays an essential role. Their spintexture entirely covers the spin unit sphere,hence a non-trivial topology. As a consequence,they cannot be destroyed, by a continoustransformation towards the uniform state,which contributes to their stability. Lessintuitive, such a topology gives specificcontributions to the dynamics, leading to anexcess of dissipation at smallest sizes and agyrotropic force that deviate them from theapplied force direction. Antiferromagneticsystems, whether they are realantiferromagnets, ferrimagnets or syntheticantiferromagnets have been predicted to enablea control of the gyrotropic effects, impossiblein simple ferromagnets, while keeping theskyrmion topology [1]. By coupling twoskyrmions with cores that are alignedantiparallel, the skyrmions have oppositegyrovectors that compensate each other, when abound state is formed. Expected deflectionlessand faster dynamics strongly motivatesinvestigations in those materials. In this talk, we will first focus on thedescription of the skyrmion dynamics inantiferromagnetic situations. We show a simpleanalytical formalism that enable to accuratelydescribe the dynamics in bound states formedby two skyrmions with opposite gyrovectors.Beyond the compensation of the gyrotropicdeflection, this formalism predicts thatskyrmions in antiferromagnets have an intrinsicmass or inertia related to the oppositegyrovectors, and that scales inverselyproportional to the antiferromagnetic couplingenergy [2]. In a second part, we show our recent results onrare-earth/transition metal ferrimagnets and Co-based synthetic antiferromagnets. These twotypes of material enable to investigate thedynamics over a large range of parameters(momentum compensation, couplingstrength...). In ferrimagnets, the ability to tunethe relative magnetization of the two chemicalspecies (by temperature or composition) 02/06/2023 13:51 Contribution of the antiferromagnetic coupling on the skyrmion dynamics in ferrimagnets and synthetic antiferromagnets https://srv3.key4events.com/key4register/AbstractList.aspx?e=42&g=e4ab0758-efd2-4b9c-835e-bf57155e5449&preview=1&print=1&aig=-1&ai=7… 2/2 enables to vary the magnitude of the twogyrovectors. We demonstrate an efficientskyrmion motion induced by spin-orbit torques[3] and show that the gyrotropic deflection canbe reversed when considering temperaturesbelow (rare-earth dominated momentum) andabove (transition metal momentum) themagnetic compensation temperature [3]. Insynthetic antiferromagnets, we show that whenthe two layers have exactly the samemagnetization, gyrotropic deflection iscancelled: skyrmions move along the appliedcurrent direction and with large velocities, upto 250 m/s [4]. These results prove thepromises of antiferromagnetic materials forskyrmionics and could serve are basis for thefuture developments . [1] Barker and Tretiakov Phys. Rev. Lett. 116,147203 (2016); Zhang et al. Nat. Commun. 7,10293 (2016) [2] Panigrahy et al. Phys. Rev. B 106, 144405(2022) [3] Berges et al. Phys. Rev. B 106,144408(2022) [4] Berges et al. In preparation [5] Panigrahy et al. In preparation
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hal-04295835 , version 1 (20-11-2023)

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  • HAL Id : hal-04295835 , version 1

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Stanislas Rohart, Sujit Panigrahy, Léo Berges, Joao Sampaio, Alexandra Mougin. Contribution of the antiferromagnetic coupling on the skyrmion dynamics in ferrimagnets and synthetic antiferromagnets. EMRS Fall Meeting, EMRS, Sep 2023, Varsovie, Poland. ⟨hal-04295835⟩
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