STUDY OF GEOMETRICAL SURFACE-BARRIER IN BI2SR2CACU2OX SINGLE-CRYSTAL BY SCANNING SPIN-PROBE

The field distribution in the Bi2Sr2CaCuzOx rectangular strip, placed into perpendicular magnetic field, was studied. The measurement of loc al field magnitude was made using the ESR microprobe moved over the sa mple surface. Our results confirm the existence of geometrical barrier for vortex motion, which is due to edge shielding current, even at hi gh magnetic fields. Changing the temperature we were able to observe t he crossover of the magnetic field profile from the dome shape, typica l for geometrical barrier (T > 30K), to the steep front penetration pi cture (T < 25K) of the bulk pinning case.