FIELD SWEEP RATE DEPENDENCE OF DC AND AC MAGNETIZATION - COMPARISONS WITH FLUX-CREEP AND DYNAMIC MAGNETIZATION MODELS

The effect of Dc field sweep rate on Dc and Ac magnetizations has been studied in melt-textured YBCO superconductors. Comparisons of results are made with the flux creep and dynamic magnetization models, and it is shown that both the anisotropy in the rate dependence of Dc magnet ization, and the absence of history dependence in Ac susceptibility (w ith Dc sweeps) is consistent with the dynamic magnetization models. Fo r low fields, however, the flux creep contribution to rate dependence may still be very significant, as demonstrated by comparisons of norma lized retaxation rate (d In m/d In t) and (1/m)(dm/d In H).