Magnetic-Field Dependence of Radio-Frequency Flux Penetration in Type-II Superconductors

The magnetic-field dependence of the penetration of radio-frequency fields has been measured in type-II superconductors. We discuss information obtained concerning the mixed state, the superconducting surface sheath, and superconducting cylindrical thin films. Some of the results, such as structure near $H_{c2\mathrm{}}$, are interpreted in terms of vortex motion and effects of the sheath. Results pertaining to the sheath are compared with the calculations of Fink and Kessinger and of Maki. Other results in the mixed state are related to surface impedance calculations of Maki and of Caroli and Maki, based on the microscopic theory. Penetration depth measurements in the films agree better with a naive model than with Pincus's theory.