Microscopic analysis of low-frequency flux noise in YBa2Cu3O7 direct current superconducting quantum interference devices

Doenitz, D.; Straub, R.; Kleiner, R.; Koelle, D.
December 2004
Applied Physics Letters;12/13/2004, Vol. 85 Issue 24, p5938
Academic Journal
We use low-temperature scanning electron microscopy combined with superconducting quantum interference device (SQUID) detection of magnetic flux to image vortices and to investigate low-frequency flux noise in YBa2Cu3O7 thin film SQUIDs. The low-frequency flux noise shows a nonlinear increase with magnetic cooling field up to 60 μT. This effect is explained by the surface potential barrier at the SQUID hole. By correlating flux noise data with the spatial distribution of vortices, we obtain information on spatial fluctuations of vortices on a microscopic scale, e.g., an average vortex hopping length of ∼10 nm.


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