High-field behaviour of the magnetic response of a hard superconducting thin disc and application to hysteresis loops of YBaSUB2/SUBCuSUB3/SUBOSUB7- delta/SUBthin films

摘要

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 correlated. It is shown that at the high-field limit H>>Hcwhere Hcis the characteristic field for the disc, the virgin magnetic moment, hysteresis loops and current distribution in the disc that come from the above models (with the exception of the 'reverse legs' of the hysteresis loops) have the same functional dependences. It is shown that the assumptions of Sun's model successfully describe the critical 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 expression Jc(Ha)=Jc(0)/(1+ mod Hamod B0) successfully reproduces the experimental hysteresis loops for epitaxial YBCO thin films.