Suppression of field-induced low-frequency noise in high-Tc SQUID magnetometers using slotted flux dams

Abstract

We fabricated directly coupled dc SQUID magnetometers which had a mesh structure from YBa2Cu3O7-x thin films deposited on SrTiO3 bicrystal substrates. A pickup coil had two flux dams of grain boundary junction (GBJ) near the SQUID. In order to suppress the flux motion in the flux dams, we formed 5 μm wide strip lines and slots across the GB of the flux dams. The flux noise was measured after applying static magnetic field in a magnetically shielded room. The flux-locked-loop output was stable and the increase of low-frequency noise was suppressed up to an applied field of 40 μT. It is suggested that slotted flux dams are useful to suppress the low-frequency noise in the change of applied field. © 2001 Elsevier Science B.V. All rights reserved.