Pinning potentials of the vortex lattice in YBCO crystals in the peak effect region

Abstract

Memory effects in the dynamic response of the vortex lattice (VL) in type II superconductors and its relationship with the controversial peak effect, have attracted great interest for a long time. In the last years, these features have been observed in YBCO single crystals, with the DC magnetic field tilted away from the twin planes and were related with robust dynamical states characterized by different degrees of mobility. Recently, we reported that the previous dynamical history of the VL can modify not only its dynamic response, but can even modify its static properties as well. In the present work, we try to understand the nature of the peak effect in YBCO crystals by sensing the effective AC penetration depth in the linear Campbell regime. We report history dependent effective pinning potential well curvatures and study the stability of the different static configurations. Interestingly, we observe that the more pinned VL configuration is not the more stable. Results agree with a dynamic scenario undergoing the Peak Effect. © 2004 Elsevier B.V. All rights reserved.