A three-junction SQUID-on-tip with tunable in-plane and out-of-plane magnetic field sensitivity

TL;DR

This paper introduces a nanoscale three-junction SQUID-on-tip capable of independently measuring in-plane and out-of-plane magnetic fields with high sensitivity, advancing nanoscale magnetic imaging techniques.

Contribution

The development of a three-dimensional, tunable SQUID-on-tip that can detect magnetic field components in multiple directions with high sensitivity.

Findings

Demonstrated tunable sensitivity to in-plane and out-of-plane magnetic fields.

Achieved spin sensitivity better than 5 μ_B/Hz^{1/2}.

Analyzed interference patterns both numerically and experimentally.

Abstract

Nanoscale superconducting quantum interference devices (SQUIDs) demonstrate record sensitivities to small magnetic moments, but are typically sensitive only to the field component that is normal to the plane of the SQUID and out-of-plane with respect to the scanned surface. We report on a nanoscale three-junction Pb SQUID which is fabricated on the apex of a sharp tip. Because of its three-dimensional structure, it exhibits a unique tunable sensitivity to both in-plane and out-of-plane fields. We analyze the two-dimensional interference pattern from both numerical and experimental points of view. This device is integrated into a scanning microscope and its ability to independently measure the different components of the magnetic field with outstanding spin sensitivity better than $5\ \frac{\mu_B}{\mathrm{Hz}^{1/2}}$ is demonstrated. This highlights its potential as a local probe of nanoscale magnetic structures.