Fluxon viscosity in high-Tc superconductors

We present a phenomenological model for the frequency-dependent fluxon complex resistivity in which the fluxon viscosity is a central parameter. We use the high-frequency limit of this model to extract from microwave transmission measurements through thin superconducting films in the presence of a magnetic field. The measured value of allows a critical check of the model at low frequencies. The viscosity is anisotropic and consistent with anisotropic effective mass ratios of =(mc/ma)1/2=58 for Y-Ba-Cu-O and =1215 for Bi-Sr-Ca-Cu-O.