Skyrmion Brownian Circuit Implemented in Continuous Ferromagnetic Thin Film

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 SiO$_2$ capping to stabilize the skyrmion formation. The patterned SiO$_2$ 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 SiO$_2$ capping. This technique enables the efficient control of skyrmion-based memory and logic devices, as well as Brownian computers.