Consistent estimation of the critical current density of a   superconductor from hysteresis loops
  It has been noticed that the critical current density Jc of some of the superconducting samples, calculated on the basis of Bean model, increases with increasing magnetic field H up to a significant range above H=0. This is an inconsistent behavior of Jc since the theory of Kim and the theories based on vortex dynamics, all, lead to decreasing Jc with increasing H for H > 0. It has been argued that a realistic variation of Jc for low H may be obtained within Bean framework by redefining the width of the hysteresis loop. The new definition of the loop width is guided by the requirement that Jc stays as close to the Jc of the theory of Kim as possible. Illustrative calculations of Jc show its considerable enhancement over the Bean values. 
Ratan Lal