300‐Times‐Increased Diffusive Skyrmion Dynamics and Effective Pinning Reduction by Periodic Field Excitation

Abstract

Thermally induced skyrmion dynamics as well as skyrmion pinning effects in thin films have attracted significant interest. While pinning poses challenges in deterministic skyrmion devices and slows down skyrmion diffusion, for applications in non-conventional computing, both pinning of an appropriate strength and skyrmion diffusion speed are key. Here, we employ periodic field excitations to realize an increase of the skyrmion diffusion by more than two orders of magnitude. Amplifying the excitation, we report a drastic reduction of the effective skyrmion pinning and observe a transition from pinning-dominated diffusive hopping to dynamics approaching free diffusion. By tailoring the field oscillation frequency and amplitude, we demonstrate continuous tuning of the effective pinning and skyrmion dynamics, which is a key asset and enabler for nonconventional computing applications. We find that the periodic excitations additionally allow us to stabilize skyrmions at different sizes for field values that are inaccessible in static systems, opening up new approaches to ultra-fast skyrmion motion by transiently exciting moving skyrmions.Received: ((will be filled in by the editorial staff))Revised: ((will be filled in by the editorial staff))

Chiral Skyrmions Interacting with Chiral Flowers

“…The skyrmion dynamics is essential for skyrmionic devices. The dynamics of chiral skyrmions stabilized by chiral exchange interactions , in ferromagnets include two aspects, i.e., the motion driven by applied forces − , and the spontaneous diffusion induced by thermal fluctuations. − For example, a skyrmion driven by the spin–orbit torques may show the skyrmion Hall effect, ,,, where the skyrmion moves at an angle with respect to the applied current direction. On the other hand, a skyrmion driven by thermal effects may show the Brownian gyromotion, − ,,,,− , where the skyrmion tends to move in circular trajectories during the random walk.…”