Complex inductance, excess noise, and surface magnetism in dc SQUIDs.
We have characterized the complex inductance of dc SQUIDs cooled to millikelvin temperatures. The SQUID inductance displays a rich, history-dependent structure as a function of temperature, with fluctuations of order 1 fH. At a fixed temperature, the SQUID inductance fluctuates with a 1/f power spectrum; the inductance noise is highly correlated with the conventional 1/f flux noise. The data are interpreted in terms of the reconfiguration of clusters of surface spins, with correlated fluctuations of effective magnetic moments and relaxation times.
Sendelbach
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Department of Physics, University of Wisconsin, Madison, Wisconsin 53706, USA.
Hover
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Mück
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McDermott
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