Scanned probe imaging of nanoscale magnetism at cryogenic temperatures with a single-spin quantum sensor

TL;DR

This paper demonstrates cryogenic temperature magnetic imaging at the nanoscale using nitrogen-vacancy centers in diamond, achieving high spatial resolution and sensitivity, enabling new insights into condensed matter systems.

Contribution

It extends NV-based magnetic imaging to cryogenic temperatures, allowing nanoscale magnetic studies of materials with non-trivial magnetic order.

Findings

Achieved 6 nm spatial resolution at 6 K

Demonstrated imaging of vortices in a superconductor

Benchmarking with magnetic hard disk sample

Abstract

High spatial resolution magnetic imaging has driven important developments in fields ranging from materials science to biology. However, to uncover finer details approaching the nanoscale with greater sensitivity requires the development of a radically new sensor technology. The nitrogen-vacancy (NV) defect in diamond has emerged as a promising candidate for such a sensor based on its atomic size and quantum-limited sensing capabilities afforded by long spin coherence times. Although the NV center has been successfully implemented as a nanoscale scanning magnetic probe at room temperature, it has remained an outstanding challenge to extend this capability to cryogenic temperatures, where many solid-state systems exhibit non-trivial magnetic order. Here we present NV magnetic imaging down to 6 K with 6 nm spatial resolution and 3 {\mu}T/$\sqrt{\mbox{Hz}}$ field sensitivity, first benchmarking the technique with a magnetic hard disk sample, then utilizing the technique to image vortices in the iron pnictide superconductor BaFe$_2$(As$_{0.7}$P$_{0.3}$)$_2$ with $T_c$ = 30 K. The expansion of NV-based magnetic imaging to cryogenic temperatures represents an important advance in state-of-the-art magnetometry, which will enable future studies of heretofore inaccessible nanoscale magnetism in condensed matter systems.