Low-frequency AC susceptibility due to the interplay of loss mechanisms in HTS

The analysis of low-frequency ac susceptibility is complicated because the hysteretic losses due to pinning and the eddy-current losses are not simply additive. We show that the electromagnetic response of both ideal and nonideal type-II superconductors can be well described with a common nonlinear response function. This function makes a consistent description of the crossover from the power-law E(J) of flux-creep to the ohmic flux-flow regime. We interpret the scaling behavior of ac susceptibility with this nonlinear equation.