ANALYSIS OF THE CURRENT-VOLTAGE CHARACTERISTICS AND TRANSPORT CRITICAL-CURRENT DENSITY OF SUPERCONDUCTING YBA2CU3O7-DELTA IN THE SELF-FIELD APPROXIMATION

The temperature and sample size (width, thickness, and cross-sectional area) dependences of the zero-field current-voltage characteristics and transport critical current density J(c) of YBa2Cu3O7-delta have been studied by using the motion of the flux lines which depends on the pinning force F-p and the Lorentz forces F-L. We have obtained analytical expressions for the sample size and temperature dependences of the critical current density and current-voltage characteristics, which are in reasonable agreement with most of the experimental data published previously. It has been shown that the viscous drag coefficient eta Of the medium changes with temperature as eta = eta(0)[1 - (T/T-c)(2)]. We have also found that the pinning force F-p is proportional to [B(T)](3/2) which implies that the diameter of the spherical pinning centres is larger than the coherence length as in the case of conventional hard superconductors.