Flux-motion related AC losses in high T/sub c/ superconductors

The AC losses of high-temperature superconductors in the flux-depinned mixed-state have been treated using the classical magnetic diffusion equation in conjunction with various models of flux-motion. With the imaginary part representing the AC losses, the field- and frequency-dependent AC susceptibilities were investigated. The imaginary component was found to obey a scaling rule with a characteristic frequency, estimated to be approximately 10/sup 5/-10/sup 9/ Hz, that depended on the sample size and normal state resistivity. This frequency range agrees with earlier experimental results, which could not be accounted for previously based upon the notion of thermally activated hopping of vortices. The frequency scaling behaviors using flux-creep and flux-flow models are presented.>