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Sensitive Method of Measuring Microwave Surface Impedance of Superconducting Films

Published online by Cambridge University Press:  26 February 2011

H. Jiang
Affiliation:
Northeastern University, Boston, Massachusetts 02115
H. How
Affiliation:
Northeastern University, Boston, Massachusetts 02115
A. Widom
Affiliation:
Northeastern University, Boston, Massachusetts 02115
C. Vittoria
Affiliation:
Northeastern University, Boston, Massachusetts 02115
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Abstract

We used a microwave technique in which a small strip of YBCO film is induced to self-resonant in order to measure the surface impedance at 21 GHz. Both the amplitude and phase of the transmission coefficient, S21, as a function of frequency was measured at different temperatures. The surface resistance, Rs, was obtained from at resonant frequency, where Z0is the waveguide impedance. The surface reactance, Xa was obtained from the measurement of frequency shift with temperature. We found that Ra changed about 3 orders of magnitude as T decreased from 90K to 80K reaching a low value of 4.9 × 10−4μ. From Ra and Xa we deduced the London penetration depth to be λ ∼ 1800Å at 4K and 8000Å at 86.5K.

Type
Research Article
Copyright
Copyright © Materials Research Society 1992

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References

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