ACTIVATION-ENERGIES FOR DEPINNING OF VORTICES FROM INTRINSIC AND EXTRINSIC PINNING CENTERS IN HIGH T-C SUPERCONDUCTORS

The anisotropy of the vortex motion has been studied on textured sampl es of Bi based superconductors. The Hall (transverse) voltage which is even function of the magnetic field has been discussed in terms of th e guided motion of vortices due to the intrinsic pinning thanks to the layered structure of material under study. An increase of the tempera ture suppresses the anisotropy of pinning and the even transverse volt age disappears. The proposed thermal activation mechanism of vortex mo tion has been used for study of the depinning of vortices from intrins ic pinning centres connected with the presence of CuO2 planes and from the other pinning centers present in the sample.