Flux Dynamics and Electronics Anisotropy in High Temperature Superconductors.

The dissipation below T sub c in external fields up to 12T has been studied in five groups of high temperature cuprates. The dissipation is due to Lorentz-force driven flux motion and is least pronounced in the compound with the smallest electronic anisotropy (Ba sub 2 YCu sub 3 O sub 7). A crossover temperature T sub x is defined at which the effective activation energy for flux motion is ~kT. This T sub x is material specific. An H-T phase diagram is presented for Ba sub 2 YCu sub 3 O sub 7 and Bi sub 2 Sr sub 2 CaCu sub 2 O sub 8 demonstrating the qualitative similarities and quantitative differences in the dissipation behavior in these two compounds.