Angular dependence of flux pinning in high-T c superconducting films

Abstract

We have investigated the angular dependence of the dissipative characteristics of YBa 2>Cu 3>O 7−y(>YBCO) and >Bi 2>Sr 2>CaCu 2>O 8−y(>BSCCO) films by measuring the resistivity in a field. The dissipation can be described by the thermal activated flux creep model, > R= R O exp(−U(H,T,θ)/k BT). U depends on the magnetic field as well as the angle, θ, the magnetic field makes with the c-axis. We found that the activation energy of YBCO films decreases by a factor of 2 while that of BSCCO films decreases by a factor of about 10 in > H = 5.5>T and at > T/ T c = 0.93 as one varies θ from 90° to 0°, where θ is the angle between the c axis and the direction of the field.