Microwave measurements of the absorbed power in granular Y-Ba-Cu-O samples for temperatures in the range 1–50 K are reported. The hysteretic behaviors observed are attributed to the fluxon motion in the flux-creep regime. A calculation of the surface resistance, based on the hypothesis of validity of the Bean model and which qualitatively explains the experimental results, is given. The potential of the surface-resistance measurement technique at microwave frequencies to detect various types of losses (flux creep, flux flow, and Josephson-junction dephasing) is discussed.

• Received 11 November 1991

DOI:https://doi.org/10.1103/PhysRevB.45.7387