Logarithmic to Nonlogarithmic Flux Creep Transition and Magnetic Flux Hardening in Bisrcacuo Superconducting Ceramics

Hugo F. Safar, Nokia Bell Labs
C.A. Durán, Lucent
Julio Guimpel, Comisión Nacional de Energía Atómica
L. Civale, Comisión Nacional de Energía Atómica
Javier Luzuriaga, Universidad Nacional de Cordoba
Eduardo E. Rodríguez, Universidad de Buenos Aires
Francisco de la Cruz, Centro Atmico Bariloche
Carlos Fainstein, Centro Atomico Bariloche
Lynn Schneemeyer, Montclair State University
Joseph V. Waszczak, University of Washington

Abstract

A sharp temperature and field dependent transition from a logarithmic to a non-logarithmic flux creep behavior has been found in BiSrCaCuO superconductors. The transition is not followed by any noticeable change in the magnetization. However, vibrating reed measurements show that it coincides with a strong hardening of the magnetic structure. The transition occurs at fields and temperatures well below the reversibility line. The possible relation to the recently proposed flux lattice melting is discussed.