Maarten A. Brems, Mathias Kläui, and Peter Virnau
Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudingerweg 7, 55128 Mainz, Germany
Magnetic skyrmions are two-dimensional magnetic quasi-particles with interesting properties for possible future applications in memory storage devices and nonconventional computing. We have shown that skyrmions in thin film magnetic multilayers exhibit thermal diffusion [1]. These properties make skyrmions promising candidates for signal carriers (tokens) in Brownian computing, which exploits thermal fluctuation for computations. We design a crossing-free layout (Fig. 1) for a composite half-adder module to overcome the problem that crossings generate for the fabrication of circuits [2]. To address the key issue of slow computation based on thermal excitations, we propose to combine artificial diffusion induced by an external excitation mechanism [2,3]. For magnetic skyrmions, induced diffusion by spin-orbit torques or other mechanisms can increase the computation speed by several orders of magnitude. This method can be employed to accelerate conventional Brownian computing as necessary and thereby greatly enhance the application scenarios of token-based computing for instance for low power devices such as autonomous sensors.
Fig. 1. Crossing-free Brownian half-adder containing hubs (gray circles) and ratchets (lines with triangles, and the triangle tip indicates the preferred direction of motion). The tokens (bold dots) are placed for the input 0 + 0. C-join-halves (colored squares) with same color/number can only be passed together. The colored arrows show the relevant directions for induced diffusion.
References
[1] J. Zázvorka et al., Nat. Nanotechnol. 14, 658 (2019).
[2] M. A. Brems, P. Virnau and M. Kläui, Appl. Phys. Lett. 119, 132405 (2021).
[3] M. A. Brems, P. Virnau and M. Kläui, European patent disclosure, EP21164676.5 (2021)