Temperature scaling of the flux pinning force in Bi2Sr2Ca1Cu2O8+x thin films

The electrical transport properties of Bi2Sr2Ca1Cu2O8+x thin films have been measured in the temperature range from 20 to 50 K and in external magnetic fields up to 4 T The dependence of the normalized pinning force f = F-p/F-p,F-max on the reduced magnetic field h = H/H* (H* is the irreversibility field) exhibits a scaling law behavior, indicating that a single pinning mechanism is present in the investigated temperature range. The F-p(H) curves were analyzed within the framework of the classical Anderson-Kim theory of flux creep, taking into consideration the nonlinear current dependence of the pinning energy U and its dependence on the temperature T, the magnetic field H, and the current density J. Under these assumptions a generalized formula for F-p was obtained which, assuming a suitable U(J) dependence, was able to explain the f(h) curve in the observed temperature range. (C) 1996 American Institute of Physics.