SQUID Magnetometer Based on Grooved Dayem Nanobridges and a Flux Transformer

We report noise measurements performed on a superconducting quantum interference devices (SQUID) magnetometer implementing YBa
₂
Cu
₃
O
_7-δ
grooved Dayem nanobridges as weak links. The magnetometer is realized by coupling the SQUID to a flux transformer with a two-level coupling scheme using a flip-chip approach to improve the effective area of the SQUID. The measured magnetic flux noise of the SQUID is as low as 10 μΦ
₀
/√Hz, which corresponds to an equivalent magnetic field white noise of 60 fT/√Hz above 100 Hz at T = 77 K.