Magnetisation and critical currents in high Tc powders

Magnetization curves have been measured on powders of various sizes. The hysteresis decreases with size for articles smaller than 20 microns, showing that barriers to current flow are at least this far apart. The current density is 6 x 10 to the 6th amps/sq cm at 1.5T and this is consistent with theoretical calculations of Jc. Inductive transitions are consistent with a penetration depth of about 0.5 micron at 78 K. The results of hot isostatic pressing are also discussed. 5 references