A new technique for the determination of the critical current density in   superconducting films and flat samples
  The determination of their critical current density in the whole range of the temperature below Tc is of first importance to understand the physical processes occurring in superconducting films. We describe here a technique suitable for square films based on the measurement of the magnetic moment due to the currents persisting in the superconductor after the application of a perpendicular high magnetic field. Typically, with a SQUID magnetometer, the measurement time in the whole range of temperature with a 1K interval is of 2 hours only by this technique. An intriguing aspect of the obtained results is that they are much more accurate if the current lines are supposed to be circular than if we suppose, as suggested by theoretical considerations and magneto-optical observations that they have the sample symmetry. 
Conor McLoughlin, Pierre Bernstein, Yohann Thimont and J. Siejka
cond-mat.supr-con physics.ins-det