Optimal Pinning of Vortices with Controlled Splay Configurations of Columnar Defects
Abstract
We report orders-of-magnitude enhancements of persistent currents J in Y Ba2 Cu3 O_7-δ with columnar defects arranged in a variety of splayed configurations. The largest J is obtained for a planar distribution of splay angles, P_pl(Θ), with an optimal splay angle Θ_opt = ± 5 ^circ. A comparison of P_pl(Θ) and a gaussian distribution, P_G(Θ), suggests that pinning by the latter is controlled by large-angle tails of the gaussian, which appear to enhance thermal creep rate by generating numerous intersections of splayed defects (tracks). The track crossings allow for easier vortex jumps from one track to another, giving rise to "zig-zag" configurations promoting vortex motion. Numerical simulations confirm the existence of the regimes where vortex motion is promoted rather than suppressed by splay.
- Publication:
-
APS March Meeting Abstracts
- Pub Date:
- March 1996
- Bibcode:
- 1996APS..MAR.Q2403K