HYSTERESIS IN MAGNETIC-FIELD AND FIELD-DIRECTION DEPENDENCE OF CRITICAL CURRENT IN BI2SRCACU2O8+Y

We measured the dependence of the critical current density J(c)(T, H) on angles phi and theta, the magnetic field H and the temperature T for Bi2Sr2CaCu2O8+y films with the preferred c-axis orientation prepared by a laser ablation technique, where phi is an angle between H and the basal plane for the current density J perpendicular-to H, and theta an angle between H and J in the plane comprising the c-axis and J. Characteristic features were as follows. (1) J(c)(T, H) versus phi and J(c)(T, H) versus theta had a characteristic hysteresis due to a characteristic pinning of the flux lines parallel to the c-axis. (2) When J(c)(T, H) versus phi, J(c)(T, H) versus theta and J(c)(T, H) versus T were replotted with J(c)(T, H) versus the c-axis component of the magnetic fields, these dependences were almost identical. (3) This hysteresis was reduced if the magnetic field was applied by a special procedure.