Low-frequency flux noise and visualization of vortices in a YBa2Cu3O7 dc SQUID washer with an integrated input coil

Abstract

We used low-temperature scanning electron microscopy (LTSEM) for imaging quantized magnetic flux (vortices) in direct current (dc) superconducting quantum interference devices (SQUIDs) with approximately 1 micron spatial resolution at temperature T=77 K in a controllable magnetic field up to 20 microTesla. We demonstrate that LTSEM allows to image the spatial distribution of vortices in a YBa2Cu3O7/SrTiO3/YBa2Cu3O7 multilayer thin-film structure consisting of a dc SQUID washer with an integrated input coil on top. Simultaneously, we are able to measure the low-frequency noise of the sample under test, which allows to correlate the spatial distribution of vortices with low-frequency noise in the SQUID.

3 pages, 3 figures, to be published in Appl. Phys. Lett. 06/04/2001; a pdf-file is also available at http://www.pit.physik.uni-tuebingen.de/Kleiner/papers/2001/straub01_apl.pdf