# Precision determination of a fluxoid quantum's magnetic moment in a superconducting micro-ring

## TL;DR

This study precisely measures the magnetic moment of a superconducting Nb micro-ring using cantilever magnetometry, providing insights into fluxoid behavior and validating theoretical models at cryogenic temperatures.

## Contribution

It introduces a method for high-precision measurement of fluxoid magnetic moments in superconducting micro-rings, advancing the understanding of their magnetic properties.

## Key findings

- Magnetic moments of fluxoids and diamagnetic response measured with subfemtoampere-square-meter resolution.
- Results agree with the Brandt and Clem theoretical model within measurement accuracy.
- Demonstrates the potential for using micro-rings in quantum and metrological applications.

## Abstract

Using dynamic cantilever magnetometry and experimentally determining the cantilever's vibrational mode shape, we precisely measured the magnetic moment of a lithographically defined micron-sized superconducting Nb ring, a key element for the previously proposed subpiconewton force standard. The magnetic moments due to individual magnetic fluxoids and a diamagnetic response were independently determined at T = 4.3 K, with a subfemtoampere-square-meter resolution. The results show good agreement with the theoretical estimation yielded by the Brandt and Clem model within the spring constant determination accuracy.