BROADENING OF RESISTIVE TRANSITION AND IRREVERSIBILITY LINE FOR EPITAXIAL YBa₂Cu₃O_7-\delta THIN FILM

The broadening of resistive transition of c axis oriented epitaxial YBCO thin film has been measured for three configurations: (1) H∥c and H⊥I; (2) H∥ab plane and H⊥I; (3) H∥ab plane and H∥I in magnetic field up to 8 Teala(T), and for different angle \theta of magnetic field relative to the ab plane with H = 4T. The results obtained indicate that the broadening of resistive transition is mainly determined by the angle \theta, but is hardly related to the angle \alpha made between magnetic field and tran sport current in ab plane. This means that the broadening of resistive transition is not determined by flux motion drived by apparent Lorentz force. Au expression of angular dependence of irreveraibility line has been given.