Flux-reorientation in irradiated YBa2Cu3O7 and Bi2Sr2CaCu2O8 crystals

Pinning by columnar defects in irradiated YBa 2 Cu 3 O 7 (YBCO) and Bi 2 Sr 2 CaCu 2 O 8 (BSCCO) crystals is most efficient when the field is parallel to the defect. However, in the low field limit the remanent magnetization is independent of the direction of the field, indicating that the fluxons flop towards the columnar defect. The flux-flop is almost temperature independent in YBCO and strongly temperature dependent in BSCCO due to the different nature of the vortices