Hysteretic and ac dynamic losses of high Tc superconductors by numerical solution of the nonlinear magnetic diffusion equation

The complex ac susceptibility (chi) of high T-c superconducting materials has been described in terms of hysteretic and dynamic losses. By including both flux creep and flux flow resistivities in the expression of the flux diffusivity, induction profiles have been numerically calculated from the non linear flux diffusion equation. The imaginary part of chi has been evaluated as function of temperature, frequency and amplitude of the applied magnetic field. The role of pinning and dynamic losses occuring in high T-c materials is discussed.