MAGNETIC IRREVERSIBILITY IN SUPERCONDUCTORS CHARACTERIZED BY SHIELDING CURRENT-DENSITY

The irreversibility line (IL) is an important characteristic of superc onducting materials. We compare in this paper the IL's obtained from A C susceptibility with those determined from quasistatic magnetisation loops recorded on a SQUID susceptometer. The basis for the comparison is in calculating the equivalent density of persistent currents flowin g in the sample. In addition to these currents, those ones depending o n the rate of magnetic field change contribute to the magnetic respons e of a sample. We observed satisfying agreement when comparing II's fr om SQUID and AC susceptometer experiments.