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arXiv · 1803.07636

A micro-SQUID with dispersive readout for magnetic scanning microscopy

Farshad Foroughi·Jan-Michael Mol·Tristan Mueller·John R. Kirtley·Kathryn A. Moler·Hendrik Bluhm
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Abstract

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 $80\;\mathrm{n}Φ_0 \mathrm{Hz}^{-1/2}$ 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 $30\;\mathrm{n}Φ_0\mathrm{Hz}^{-1/2}$ at 100 mK, which corresponds to $7.5\;\mathrm{μ_B Hz^{-1/2}}$ for a magnetic moment located at the center of the pickup loop.

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Farshad Foroughi, Jan-Michael Mol, Tristan Mueller, John R. Kirtley, Kathryn A. Moler, Hendrik Bluhm. 2018-03-20. A micro-SQUID with dispersive readout for magnetic scanning microscopy. https://doi.org/10.1063/1.5030489

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