FREQUENCY-DEPENDENCE OF AC MAGNETIC RESPONSE IN TYPE-II SUPERCONDUCTORS

The ac magnetic response in type-II superconductors was analyzed on th e basis of flux creep theory. A modified model was proposed to describ e the variation of current density in a sample immersed in an alternat ing field, which simultaneously took into account the sweeping applied field and the flux creep inside the sample. The frequency dependent a c susceptibility of a textured YBa2Cu3O7 bulk sample was measured and explained in this model, Also discussed was the relation between our m odel and other models that appeared in literature.