Grooved Dayem Nanobridges As Building Blocks Of High-Performance Yba2cu3o7-Delta Squid Magnetometers

We present noise measurements performed on a YBa2Cu3O7-delta nanoscale weak-link-based magnetometer consisting of a superconducting quantum interference device (SQUID) galvanically coupled to a 3.5 x 3.5 mm(2) pick-up loop, reaching white flux noise levels and magnetic noise levels as low as 6 mu Phi(0)/root Hz and 100 fT/root Hz at T = 77 K, respectively. The low noise is achieved by introducing grooved Dayem bridges (GDBs), a new concept of a weak link. A fabrication technique has been developed for the realization of nanoscale grooved bridges, which substitutes standard Dayem bridge weak links. The introduction of these novel key blocks reduces the parasitic inductance of the weak links and increases the differential resistance of the SQUIDs. This greatly improves the device performance, thus resulting in a reduction of the white noise.