T. Dohi1, M. Weißenhofer2, N. Kerber1,3, F. Kammerbauer1, Y. Ge1, K. Raab1, J. Zázvorka4, M.-A. Syskaki1,5, A. Shahee1, M. Ruhwedel6, T. Böttcher6, P. Pirro6, G. Jakob1,3, U. Nowak2, and M. Kläui1,3
1 Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudingerweg 7, 55128 Mainz, Germany
2 Fachbereich Physik, Universität Konstanz, DE-78457 Konstanz, Germany
3 Graduate School of Excellence Materials Science in Mainz, Staudingerweg 9, 55128 Mainz, Germany
4 Institute of Physics, Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, Prague 12116, Czech Republic
5 Singulus Technologies AG, 63796 Kahl am Main, Germany
6 Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, Gottlieb-Daimler-Straße 46, 67663 Kaiserslautern, Germany
Magnetic skyrmions, topologically stabilized quasi-particles, are attractive for the intriguing responses governed by their topology [1]. However, some of the topologydependent features of magnetic skyrmions are recognized as an obstacle to device applications, e.g. the skyrmion Hall effect [2,3], which describes a perpendicular motion component to the current flow direction that can lead to the annihilation of skyrmions encoding information at a wire edge. Likewise, theory predicts that the gyrotropic force originating from the finite topology gives rise to a drastic decrease of the diffusion coefficient [4–6]. While being advantageous for deterministic devices, this diffusion suppression is a key obstacle for unconventional devices that are actively making use of stochasticity [7]. Here we demonstrate that a synthetic antiferromagnetic (SyAFM) system [8] with low pinning enables us to observe thermally-activated diffusive motion of antiferromagneticallycoupled skyrmions as shown in Fig. 1. The systematic investigation varying the compensation ratio of magnetic moments in the magnetic sub-lattices with our analysis accounting for pinning effects allows for disentangling the influence of the topology on the diffusive motion. Our analysis reveals an at least 10 times larger diffusion coefficient for highly compensated antiferromagnetically-coupled skyrmions that is a direct consequence of the reduction of the effective topological charge, which enables ultimately energy-efficient unconventional computing leveraging the enhanced stochasticity in antiferromagnetic systems.
Fig. 1: Temperature dependence of the diffusion coefficient for samples with various compensation ratio
References
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