Non-destructive measurement of the critical current and the current carrying length scale in superconducting crystals and films

In superconductors having a plate-like geometry, valuable information can be obtained detailed examination of the magnetic hysteresis loop. The length scale Λ on which screening currents flow, and the sheet critical current density Kc can be evaluated independently. Because of internal weak-links, Λ may be less than the sample dimension, and will change with field and temperature. Experimental results on crystals and films confirming the validity of the analysis are presented. (orig.)