The response of small SQUID pickup loops to magnetic fields

TL;DR

This paper develops detailed models for small SQUID pickup loops' magnetic response, improving interpretation of high-resolution magnetic images by solving coupled London's and Maxwell's equations for realistic sensor geometries.

Contribution

It introduces a comprehensive modeling approach for sub-micron SQUID pickup loops, enhancing the accuracy of magnetic field interpretation in scanning SQUID microscopy.

Findings

Models agree with experimental data for various magnetic sources.

Improved interpretation of sub-micron spatial resolution data.

Enhanced understanding of sensor response at small scales.

Abstract

In the past, magnetic images acquired using scanning Superconducting Quantum Interference Device (SQUID) microscopy have been interpreted using simple models for the sensor point spread function. However, more complicated modeling is needed when the characteristic dimensions of the field sensitive areas in these sensors become comparable to the London penetration depth. In this paper we calculate the response of SQUIDs with deep sub-micron pickup loops to different sources of magnetic fields by solving coupled London's and Maxwell's equations using the full sensor geometry. Tests of these calculations using various field sources are in reasonable agreement with experiments. These calculations allow us to more accurately interpret sub-micron spatial resolution data obtained using scanning SQUID microscopy.