MECHANISM OF MODULATED MICROWAVE-ABSORPTION AND FLUX DISTRIBUTION IN GRANULAR YBA2CU3OX UNDER HIGH-FIELD SWEEP

The mechanism of modulated microwave absorption (MMA) is suggested fro m the modulation (H-m) dependence in granular YBa(2)Cu(3)Ox supercondu ctor under high-field sweep. It is proposed that the MMA signal S be d ecomposed into three shape factors to interpret the experimental resul t. The VN factor arises from the difference in the number of vortices between the add (A) mode and the subtract (S) mode corresponding to th e alternating field. The CT factor arises from the appearance of the t ransition region of the shielding current in the S-mode where the abso rption is less. The SS factor arises from the difference in the surfac e slope of the flux distribution between the two modes. With increasin g H-m, the positive VN increases linearly. The positive CT increases i nitially and then decreases. The slope for the A-mode is very gentle, so that SS is negative, and it initially increases rapidly and then sa turates. These factors can reproduce the complex behavior of the H-m d ependence of S fairly well.