Calculation of magnetic flux profiles and deduction of critical current densities for type II superconductors

The critical state concept for the calculation of internal flux profiles in type II superconductors is used to model the magnetization behavior of high-T_c materials. In this application of the model, the field-dependent reversible magnetization and critical current density are incorporated flexibly into numerical solutions of the basic equations. The solutions are compared to results obtained by using the Bean (constant J_c) and Kim (field dependent J_c) approximations. The authors use theoretically calculated magnetization curves to analyze experimental magnetization data for bulk, textured Y/ErBaCuO samples obtained from their own work and from recently published work. Pitfalls and guidelines when using such measurements to obtain intrinsic material critical current densities are discussed