UC Berkeley

The skyrmion magnetic bubble in a ferromagnetic disk exhibits hypocycloidal gyrations contrary to the vortex gyration, showing a simple circular trajectory. To describe the hypocycloidal bubble gyration, a mass term is needed in Thiele's equation. In this study, we analytically derived both mass and spring constant term, which are crucial parameters for describing the bubble gyration. Values obtained by these analytic expressions were consistent with those obtained by simulations. We could find the dependences of these two terms on several external parameters, including the bubble radius. Especially using the radius's dependence, we could obtain regular polygonlike trajectories such as a square and a triangle confirmed by the numerical simulations. Based on this effective method to control the bubble gyration, the regular polygonlike trajectories of this skyrmion magnetic bubble make it possible to study the bubble gyration without time-resolved experiments. © 2014 American Physical Society.