Vortex Activation Energy and Normalized Magnetization Relaxation Rate in the YBa2Cu3O7−δ /YSZ Quasi-multilayer

Abstract

The quasi-multilayer films of YBa2Cu3O7−δ/YSZ are prepared by means of pulsed laser deposition (PLD) and a systematic study of I–V characteristic curves for the YBCO/YSZ quasi-multilayer film are presented, with magnetic fields up to 7 T and 15 K<T<80 K. The activation energy E(H,T) for flux line depinning is determined by fitting the nonlinear of the curves up to the flux flow region. And magnetization relaxation rate S(T) is also approximately obtained by a convenient way. The results show the S(T) plateau-like domain for the YBa2Cu3O7−δ/YSZ quasi-multilayer film develops at high H (∼ 7 T) at intermediate temperatures 25 K<T<55 K, while the S(T) plateau-like domain for the optimally doped YBa2Cu3O7−δ films disappears at H=2 T, which implies the defects introduced in the quasi-multilayer serve as strong pinning centers and influence the thermal activated state of the system at low bias current values.