Magnetic irreversibility in superconductors characterised by shielding current density

Abstract The irreversibility line (IL) is an important characteristic of superconducting materials. We compare in this paper the IL's obtained from AC 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 flowing in the sample. In addition to these currents, those ones depending on the rate of magnetic field change contribute to the magnetic response of a sample. We observed satisfying agreement when comparing IL's from SQUID and AC susceptometer experiments.