A SIMPLE TECHNIQUE FOR MEASURING THE TRANSITION-TEMPERATURE AT MICROWAVE-FREQUENCIES

A technique is described which enables contactless measurements at mic rowave frequencies of the superconducting transition. The approach emp loys an electrically small microwave loop antenna to sense the change in the reflected microwave signal as flux is expelled, due to the Meis sner effect, from the superconductor. Advantages of this technique inc lude the ability to measure small areas of a superconducting thin film after photolithographic patterning into a device geometry. This appro ach is very sensitive in the frequency range from 0.05 GHz to 5 GHz an d for some YBCO films a dependence of the transition temperature width on frequency has been observed. Such frequency-dependent signatures m ay provide valuable information regarding improvements in film deposit ion and device processing.