Abstract
The critical currents and activation energies related to the surface (Bean-Livingston) barrier are found for high-temperature superconductors. It is shown that the surface barrier does not undergo a temperature (exponential) suppression which is typical of the bulk pinning. Therefore the surface irreversibility dominates over the bulk one at high temperatures T {all equal to} Tc, where the bulk pinning is suppressed by thermal fluctuations. The dependencies of the surface activation energies Usurf on the external field (Usurf H- 1 2) and transport current (Usurf J- 1 2 for moderate currents) prove to be different from those for Ubulk. This helps to distinguish between the surface and bulk effects on the transport and magnetization properties of HTSC. The interplay between the surface and the bulk contribution is discussed.
| Original language | English |
|---|---|
| Pages (from-to) | 2993-2994 |
| Number of pages | 2 |
| Journal | Physica C: Superconductivity and its Applications |
| Volume | 235-240 |
| Issue number | PART 5 |
| DOIs | |
| State | Published - Dec 1994 |
Bibliographical note
Funding Information:(where 3' is the anisotropy) for AH _= (47r/c)J t~ > rneq. This condition is almost always satisfied at current densities greater than 103A/cm 2 and usual samples with d >_ 0.1 rnm. A more complicate formula in the opposite limit A H < meq we present elsewhere. In the case where a bulk pinning is present altogether with a surface barrier, the vortices should successively surmount the surface and the bulk barriers. Therefore the role of the activation energy U will play the largest of U,~,~\] and Ubulk-If U,~f > Ub~,Ik, then a small applied current jt~ should flow along the surfaces only, thus U depends on the total current Jt~. In the opposite case, where U,~,~.r < Ub~,lk, jt~ is distributed over the bulk, and U depends on the current density, Jt~/d. In the case where samples of different thicknesses d are available from the same batch, this can provide a convenient tool to distinguish between the surface and bulk barriers. L.B. is grateful to the support from the Raschi Foundation and the Israel Academy of Science. V.M.V. acknowledges the support from the Argonne National Laboratory through U.S. Department of Energy, BES-Materials Sciences, under contract No. W-31-109-ENG-38.