We have designed and characterized a micro-SQUID with dispersive readout for use in low temperature scanning probe microscopy systems. The design features a capacitively shunted RF SQUID with a tunable resonance frequency from 5 to 12 GHz, micrometer spatial resolution and integrated superconducting coils for local application of magnetic fields. The SQUID is operated as a nonlinear oscillator with a flux- and power-dependent resonance frequency. Measurements for device characterization and noise benchmarking were carried out at 4 K. The measured flux noise above 10 kHz at 4 K is 80nΦ0Hz−1/2 at a bandwidth of 200 MHz. Estimations suggest that one can benefit from parametric gain based on inherent nonlinearity of the Josephson junction and reduce the flux noise to 30nΦ0Hz−1/2 at 100 mK, which corresponds to 7.5μBHz−1/2 for a magnetic moment located at the center of the pickup loop.
@article{arxiv.1803.07636,
title = {A micro-SQUID with dispersive readout for magnetic scanning microscopy},
author = {Farshad Foroughi and Jan-Michael Mol and Tristan Mueller and John R. Kirtley and Kathryn A. Moler and Hendrik Bluhm},
journal= {arXiv preprint arXiv:1803.07636},
year = {2018}
}