HIGH-FIELD BEHAVIOR OF THE MAGNETIC RESPONSE OF A HARD SUPERCONDUCTING THIN DISC AND APPLICATION TO HYSTERESIS LOOPS OF YBA2CU3O7-DELTA THIN-FILMS

The theoretical models of Sun et al, Mikheenko and Kuzovlev and Zhu et al, for the magnetic response of a type II superconducting thin disc with an applied field normal to its surface, are discussed and correla ted. It is shown that at the high-field limit H much greater than H-c, where H-c is the characteristic field for the disc, the virgin magnet ic moment, hysteresis loops and current distribution in the disc that come from the above models (with the exception of the 'reverse legs' o f the hysteresis loops) have the same functional dependences. It is sh own that the assumptions of Sun's model successfully describe the crit ical state of a thin disc in this case and the Sun model with applied field dependence of the critical current density through a Kim-like ex pression J(c)(H-a) = J(c)(0)/(1 + \H-a\/B-0) successfully reproduces t he experimental hysteresis loops for epitaxial YBCO thin films.