STUDY OF THE LINEAR MICROWAVE-ABSORPTION IN YBA2CU3O7-DELTA CERAMIC SAMPLES FOR LOW-LEVEL OF INCIDENT POWER

The temperature dependence (35 K less than or equal to T less than or equal to 105 K) of direct microwave absorption is studied as a functio n of incident microwave power up to 30 mW, for highly compacted cerami c samples of YBa2Cu3O7-delta. It is observed that the microwave absorp tion, under zero de field, reveals a strong cavity resonance frequency shift as a function of the incident power for temperatures in the sup erconducting transition region. The absorption presents a linear behav ior with the incident microwave power in both normal and superconducti ng states. From these measurements the temperature dependence of surfa ce resistance is also obtained.