Surface influence on flux penetration into HTS bulks

The influence of surface treatment on AC loss in melt-processed quasi-singl e crystal HTS was investigated with resonance oscillations technique. We ha ve found that amplitude dependencies of AC loss on magnetic field amplitude become rather complicated after surface polishing. The experimental data s how well-distinguished dynamic crossover from absence of barrier at low rat es of field variation to its appearence at higher rates. An explanation of such a dynamic surface barrier appearance based on consideration of along s urface vortex propagation was suggested. (C) 2000 Elsevier Science B.V. All rights reserved.