Skyrmion Brownian circuit implemented in continuous ferromagnetic thin film

Abstract

The fabrication of a skyrmion circuit which stabilizes skyrmions is important to realize micro-to nano-sized skyrmion devices. One example of promising skyrmion-based device is Brownian computers, which have been theoretically proposed, but not realized. It would require a skyrmion circuit in which the skyrmion is stabilized and easily movable. However, the usual skyrmion circuits fabricated by etching of the ferromagnetic film decrease the demagnetization field stabilizing the skyrmions, and thus prevent their formation. In this study, a skyrmion Brownian circuit implemented in a continuous ferromagnetic film with patterned SiO2 capping to stabilize the skyrmion formation. The patterned SiO2 capping controls the saturation field of the ferromagnetic layer and forms a wire-shaped skyrmion potential well, which stabilizes skyrmion formation in the circuit.Moreover, we implement a hub (Y-junction) circuit without pinning sites at the junction by patterned SiO2 capping. This technique enables the efficient control of skyrmion-based memory and logic devices, as well as Brownian computers.

Anisotropic Skyrmion Diffusion Controlled by Magnetic-Field-Induced Symmetry Breaking

“…This provides a means to steer thermal skyrmion motion. This is interesting, not just from a fundamental science perspective, but also for potential applications, where, in previous studies, the authors have patterned a skyrmion circuit geometrically to steer diffusive skyrmion motion [22,24].…”

“…This is frequently based on the common view that thermal * klaeui@uni-mainz.de diffusion is strongly suppressed in magnetic systems in which damping is typically small [20]. It has been shown recently that, in specially tailored low-pinning multilayers, pure isotropic skyrmion diffusion at room temperature can be achieved [6,[21][22][23]. By changing the sample temperature, one obtains control over the diffusion strength, since the diffusion coefficient depends exponentially on the temperature, in the case of a nonflat energy landscape, as present in the experimental samples [6].…”

Skyrmion Dynamics at Finite Temperatures: Beyond Thiele’s Equation

“…The directions of the magnetic moments S span the whole unit sphere, giving rise to a finite topological charge Q ¼ 1=ð4πÞ R d 2 rS • ð∂ x S × ∂ y SÞ [1][2][3]. As they can easily be manipulated by magnetic, optical, and electrical means, skyrmions are promising candidates as elements in conventional [4] and unconventional computing [5,6] architectures. Since the first detection of isolated skyrmions [7], they have attracted considerable research interest, resulting in experimental measurements of their current-driven dynamics [8][9][10][11] and temperature-induced Brownian motion [12][13][14].…”

Physical Limitations on Fundamental Efficiency of SET-Based Brownian Circuits

“…Brownian circuit technology is designed to efficiently and reliably perform primitive logic operations in the presence of noise and fluctuations, and Single-Electron Transistor (SET) technology is proposed as an appropriate technology-base to realize these circuits, as it has been studied extensively and meets the conditions needed to process token-based signals that are subject to fluctuations [ 9 ]. Other technology bases, such as nanophotonics or skyrmions, are proposed as suitable alternatives [ 11 ]. The foundations of Brownian circuits, along with their potential realization via SET technology, is studied in a wider context in the existing literature.…”