NONLOCAL EFFECTS IN THE CRITICAL-STATE OF TYPE-II SUPERCONDUCTORS

The shapes of the vortex Lines and of the magnetic-induction lines, as well as the distribution of current densities in a superconducting sl ab with bulk pinning in tilted magnetic fields, are calculated from a macroscopic theory that takes into account the nonlocal relationship b etween vortex field and induction. The theory reproduces the main resu lts of usual critical-state models; however, differences appear at len gth scales of the order of the magnetic penetration depth. In particul ar at the front of the critical state the vortex field has a sharp ste p.