Analysis of the remanent state after full flux penetration in high-T_c single crystals

Using the high-resolution Faraday technique (HRF) and pulsed magnetic fields, domain patterns of the remanent state have been studied in high-T_c single crystals at T = 5 K. All domain patterns at fields higher than 300 mT show the appearance of inverse domains consisting of flux lines with opposite sign at the sample edges. These domains of opposite polarisation are separated by a so-called annihilation zone. The maximum intensity of the Shubnikov phase is reached at the full penetration field, H_ext = H_sc. Further enhancement of the external magnetic field causes a decay of the measured intensity due to the dependence of the pinning forces on the external field. From the obtained domain patterns we calculate the acting local volume pinning forces up to 1.3 T for YBaCuO, DyBaCuO, and Gd-BaCuO single cristals. Applying external fields larger than 300 mT shows also the influence of different microstructures on the pinning forces. The influence of the different magnetic moments of the rare earth atoms on the penetration field, H_en, and on the full-penetration field is shown. The influence of the sample geometry on the resulting domain patterns is also studied.