Magnetic, thermal, and topographic imaging with a nanometer-scale SQUID-on-cantilever scanning probe

TL;DR

This paper introduces a nanometer-scale SQUID-on-cantilever probe that combines magnetic, thermal, and topographic imaging capabilities, enabling high-resolution, sensitive scans in magnetic fields up to 1 Tesla.

Contribution

It presents a novel fabrication of a SQUID-on-cantilever with integrated thermal and magnetic sensing, enhancing nanoscale imaging techniques beyond existing methods.

Findings

Achieved a sensor with 365 nm effective diameter.

Demonstrated field sensitivity of 9.5 nT/√Hz.

Achieved thermal sensitivity of 620 nK/√Hz.

Abstract

Scanning superconducting quantum interference device (SQUID) microscopy is a magnetic imaging technique combining high-field sensitivity with nanometer-scale spatial resolution. State-of-the-art SQUID-on-tip probes are now playing an important role in mapping correlation phenomena, such as superconductivity and magnetism, which have recently been observed in two-dimensional van der Waals materials. Here, we demonstrate a scanning probe that combines the magnetic and thermal imaging provided by an on-tip SQUID with the tip-sample distance control and topographic contrast of a non-contact atomic force microscope (AFM). We pattern the nanometer-scale SQUID, including its weak-link Josephson junctions, via focused ion beam milling at the apex of a cantilever coated with Nb, yielding a sensor with an effective diameter of 365 nm, field sensitivity of 9.5 $\text{nT}/\sqrt{\text{Hz}}$ and thermal sensitivity of 620 $\text{nK}/\sqrt{\text{Hz}}$, operating in magnetic fields up to 1.0 T. The resulting SQUID-on-lever is a robust AFM-like scanning probe that expands the reach of sensitive nanometer-scale magnetic and thermal imaging beyond what is currently possible.