Plastic Vortex Motion
Strong, sparse pinning

The movie shows the initial penetration of a flux front into a sample with a low density of strong 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 randomly placed parabolic pins in this sample are at a density of n_p = 0.64 (Pinning site density) and are all of strength f_p = 3.0 (Pinning site strength) Since the pinning is strong, vortices that fall into pinning sites remain trapped for the remainder of the movie, and repel the other vortices moving through the sample. As a result, the vortices quickly form channels that wind between the pinning sites. These channels are easily distinguished by the high density of vortex trails within them. Vortices moving inside the channels never interact with pinning sites, but instead are guided by the repulsion from the pinned vortices.

Parameters and Notes

• A_p = 3.0 (Pinning strength)
• r_pin = 0.15 (Pinning radius)
• N_pin = 400 (Number of pinning sites)
• Parabolic random pinning
• Vortices dropped every 40 md steps.
• Up to 600 vortices dropped, total.
• Movie was written every 20 md steps.

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