Effects of flux dam on low-frequency noise in high-T/sub c/ SQUID magnetometers

We demonstrated that the low-frequency noise in a high-T/sub c/ superconducting quantum interference device (SQUID) magnetometer when an external magnetic field is changed could be reduced by forming slots in a flux dam. We designed and fabricated directly coupled dc SQUID magnetometers having a mesh structure and flux dams. In order to suppress the vortex motion in the flux dams, we formed 5-/spl mu/m-wide strip lines and slots across the grain boundary of the flux dams. The output of the magnetometer in a flux-locked loop (FLL) operation became stable and low-frequency noise was suppressed up to an applied field of 83 /spl mu/T in field cooling and 40 /spl mu/T for field change after zero field cooling. The importance of the structure of the flux dam in controlling the vortex motion is discussed.