High-Tc superconducting detector for highly-sensitive microwave magnetometry

We have fabricated arrays of High-T\(_c\) Superconducting Quantum Interference Devices (SQUIDs) with randomly distributed loop sizes as sensitive antennas for Radio-Frequency (RF) waves. These sub-wavelength size devices known as Superconducting Quantum Interference Filters (SQIFs) detect the magnetic component of the electromagnetic field. We use a scalable ion irradiation technique to pattern the circuits and engineer the Josephson junctions needed to make SQUIDs. Here we report on a 300 SQUIDs series array with loops area ranging from \(6\) to \(60\ \mu m^{2}\), folded in a meander line covering a \(3.5\ mm\times 8\ mm\) substrate area, made out of a \(150\)-nm-thick \(\mathrm{YBa}_2\mathrm{Cu}_3\mathrm{O}_7\) film. Operating at a temperature \(T=66\ K\) in a un-shielded magnetic environment, under low DC bias current (\(I=60\ \mu A\)) and DC magnetic field (\(B=3\ \mu T\)), this SQIF can detect a magnetic field of a few \(pT\) at a frequency of \(1.125\ GHz\), which corresponds to a sensitivity of a few hundreds of \(fT/\sqrt{Hz}\), and shows linear response over 7 decades in RF power. This work is a promising approach for the realization of low dissipative sub-wavelength GHz magnetometers.