Comparison between conventional flux creep in constant magnetic field and the effect of creep on the shape of magnetic hysteresis loops in high-Tcsuperconductors

The effect of the magnetic induction sweep rate B= delta B ext / delta t on the shape of magnetic hysteresis loops, in particular on the induced magnetic moment m ( implies/implied by critical current j c ) was calculated directly from the basic mechanism of thermally activated flux creep introduced by Anderson taking j c constant through the sample. It was found (a) that m changes linearly with ln mod B mod , and (b) that delta m/ delta ln mod B mod is equal to - delta m/ delta ln t in conventional relaxation at B ext =constant. Similar results were obtained recently from a phenomenological model using differential susceptibility chi to characterize the effect of sweeping B ext .