300-times-increased diffusive skyrmion dynamics and effective pinning reduction by periodic field excitation
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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, periodic field excitations
are employed to realize an increase of the skyrmion diffusion by more than two
orders of magnitude. Amplifying the excitation, a drastic reduction of the effec tive skyrmion pinning, is reported, and a transition from pinning-dominated dif fusive hopping to dynamics approaching free diffusion is observed. By tailoring
the field oscillation frequency and amplitude, a continuous tuning of the effec tive pinning and skyrmion dynamics is demonstrated, which is a key asset and
enabler for non-conventional computing applications. It is found that the peri odic excitations additionally allow stabilization of skyrmions at different sizes for
field values that are inaccessible in static systems, opening up new approaches
to ultrafast skyrmion motion by transiently exciting moving skyrmions.