Plastic Vortex Motion
Clustered pinning

The movie shows the initial penetration of a flux front into a sample with clustered pinning sites. We add vortices at a constant rate to an unpinned region at the left edge of the sample, creating a gradient in vortex density that drives the vortices into the pinned region. Circles represent vortices, and lines are drawn tracing the path each vortex follows through the sample.

The parabolic pins in this sample are placed in randomly located clusters. The density of an equal number of uniformly placed pins is n_p = 0.80 (Pinning site density) and the pins are all of strength f_p = 3.0 (Pinning site strength) Vortices that fall into the very strong pinning sites remain pinned for the rest of the movie and repel the other vortices moving through the sample. Vortices fill the pinning sites on the outer edges of the clusters of pins and prevent other vortices from reaching the pinning sites in the center of the pinning clusters. As a result, a large number of the pinning sites are ineffective and empty. The large spaces between pinning clusters offer routes of unimpeded vortex motion, and all moving vortices follow these broad channels, guided by the repulsion from the vortices pinned at the edges of the clusters.

Parameters and Notes

• A_p = 3.0 (Pinning strength)
• r_pin = 0.15 (Pinning radius)
• N_pin = 500 (Number of pinning sites)
• Parabolic clustered pinning
• All the pinning sites are the same strength.
• Vortices dropped every 40 md steps.
• Up to 600 vortices dropped.
• Movie was written every 20 md steps.

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Created by: Cynthia Olson and Jared Groth
Last modified: 12/18/96