Investigation of electrical and magnetic properties of high temperature superconductors with experimental and modeling

Investigation of Electrical and Magnetic Properties of High Temperature Superconductors with Experimental and Modeling In this study, electrical and magnetic properties of high temperature superconductors have been investigated by means of both experimental measurements and modeling calculations of magnetization, critical current density and AC susceptibility. Three different groups of YBCO high temperature superconductors, namely group A, B and C, have been used in this study. Group A was produced by solid state reaction technique. Group B was fabricated by Flame-Quench-Melt-Growth (FQMG) method. Group C was prepared by solid state reaction method, where sample CI and C2 are for 0 wt% ZnO added (pure) YBCO and 1 wt% ZnO added YBCO, respectively. Experimental isothermal magnetization curves (M-H loops) at 77 K for sample A and B were measured by a commercial VSM. Some superconducting parameters were determined from the comparison of the experimental curves and the best fit curves from the calculations using the critical state model (CSM) including Meissner surface current. E-J characteristics for sample CI and C2 were measured by four probe technique at 77 K in the presence of various magnetic fields. The flux creep parameter was obtained from the comparison of the experimental E-J curves and calculated best fit curves. Upon zero field cooling (ZFC) process, the field dependence of the critical current density was measured at 77 K in first field increasing and subsequently field decreasing case. Hence Jc- B hysteresis curves were obtained and discussed in the framework of the CSM. AC susceptibility measurements for sample CI and C2 were performed as a function of temperatures at constant frequency and various AC field amplitudes in the absence and presence of DC field. In the presence of DC field, AC loss peaks traces interesting valley behavior. Theoretical calculations based on the CSM reproduced successfully the observed measurements in both samples. Key Words: High Temperature Superconductors, Magnetization Curves, Critical State Model, Critical Current Density, AC Susceptibility, AC Loss Valley VII