Microwave vortex dissipation of superconducting Nd-Ce-Cu-O epitaxial films in high magnetic fields

The microwave vortex dissipation of superconducting Nd1.85Ce0.15CuOx epitaxial films is investigated by use of a sapphire dielectric-ring resonator in the whispering gallery modes, and in dc magnetic fields ranging from 0 to 25 kG. By extending the Coffey-Clem model to the thin-film and finite-grain-size limit, we infer important material parameters, including the irreversibility line, vortex pinning potential, pinning force constant and viscosity, through a direct least-squares fit to the microwave-absorption data. © 1993 The American Physical Society.