Properties of Grooved Dayem Bridge based YBa${}_2$Cu${}_3$O${}_{7-\delta }$ Superconducting Quantum Interference Devices and Magnetometers

The transport properties of a YBa${}_2$Cu${}_3$O${}_{7-\delta }$ superconducting quantum interference device (SQUID) based on grooved Dayem bridge weak links are studied as a function of temperature: at high temperatures ($60$K$<T<T_{\mathrm{c}}=89$~K) the weak links show properties similar to SNS 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 pick-up loops: at $T=77$~K, magnetic field white noise levels as low as $63$~fT/$\sqrt{\mathrm{H}\mathrm{z}}$ have been achieved.