Constricted diamagnetic hysteresis loops observed for the high T/sub c/ superconductors

Magnetic hysteresis loops, ac susceptibility, and resistivity measurements have been made on a Ba2 YCu3 O/sub 7-//sub x/-type high- T/sub c/ superconductor. The shape of the hysteresis loops well below T/sub c/ are reminiscent of constricted hysteresis loops observed in certain ferromagnetic materials which are usually associated with magnetic aftereffects. Similar dynamic effects, with a time constant on the order of 10 s at 40 K, are shown to be present in the superconducting material. This dynamic magnetic viscosity effect is in addition to the flux creep observed for longer time periods