Magnetization of Gd diffused Yba₂Cu₃O_7-x superconductor：Experiment and theory

The magnetization of Gd diffused YBa₂Cu₃O_7-x is measured by a vibrating sample magnetometer (VSM) at selected temperatures (5, 25, 50, 77 K). The experimental results for the magnetization are analyzed in the critical state framework involving Kim-Anderson field dependence J_c(H) = J_c0/(1+|H>|/H₀)ⁿ of critical current density and equilibrium magnetization M_eq. It is found that the inclusion of the equilibrium magnetization becomes more important at higher temperatures. At 77 K, the shape of the isothermal M-H hysteresis curve is governed by the equilibrium magnetization. Some superconducting parameters are determined by fitting the calculated curves to the experimental data.