Fishtail effect and magnetic relaxation in anisotropic flat superconductors

The magnetic moment M and the normalized creep rate S of an anisotropic thi n superconducting disk in a transverse magnetic field H are calculated. The dependence of the critical current density j(c) on the direction of the ma gnetic induction B is assumed to have a peak when B is perpendicular to the plane of the sample. in this case nonmonotonic H dependences of M (fishtai l effect) and of S can occur even with monotonically decreasing j(c)(\B\) a nd U-u(\B\) where U-u is the effective depth of a flux-pinning well. In the framework of this approach the following two features of the fishtail effe ct in YBaCuO single crystals can be explained: the scaling of M and the cor relation between S(H) and the H dependence of d In\M(H)\/d In H. (C) 2000 E lsevier Science B.V. All rights reserved.