Critical Current of Superconducting ${\rm YBa}_{2}{\rm Cu}_{3}{\rm O}_{7-\delta }$ Films With Different In-Plane Orientations

By using a pulsed-laser deposition (PLD) technique, we grow high quality YBa₂Cu₃O_7-delta films on YSZ (Yt-stabilized Zr) substrates with 0-degree and 45-degree in-plane orientations at 810degC and 690degC respectively. Surprisingly, despite the large difference in growth temperature the qualities of the films are almost the same. To study the subtle differences between these two types of films, we measured both the temperature and magnetic field dependencies of the critical current. Although there is very little difference in their magnetic field dependence, there is a distinct temperature dependence, i. e. J_c(1 - T/T_c) proportional to (1 - T/T_c)^5/4 for 0 degree in-plane orientation and proportional to (1 - T/T_c)^3/2 for 45 degree in-plane orientation at temperatures near T_c. We also studied the critical current densities with different fractions of mixed orientations, and found an empirical formula J_c prop e^5alpha where alpha is the fraction of the majority domain.