Properties of grooved Dayem bridge based YBa2Cu3 O 7 - δ superconducting quantum interference devices and magnetometers

The transport properties of a YBa2Cu3 O 7 - δ superconducting quantum interference device (SQUID) based on grooved Dayem bridge weak links are studied as a function of temperature: at high temperatures (60 K < T < T c = 89 K), the weak links show properties similar to superconductor-normal conductor-superconductor junctions, while at temperatures below 60 K, the weak links behave like short Dayem bridges. Using these devices, we have fabricated SQUID magnetometers with galvanically coupled in-plane pickup loops: at T = 77 K, magnetic field white noise levels as low as 63 fT/ Hz have been achieved