Optically active spin defects hosted in hexagonal boron nitride ($h$-BN) are promising candidates for the development of a two-dimensional (2D) quantum sensing unit. Here, we demonstrate quantitative magnetic imaging with $h$-BN flakes doped with negatively charged boron-vacancy ($V_{\mathrm{B}}^{-}$) centers through neutron irradiation. As a proof-of-concept, we image the magnetic field produced by ${\mathrm{Cr}\mathrm{Te}}_2$, a van der Waals ferromagnet with a Curie temperature slightly above 300 K. Compared to other quantum sensors embedded in 3D materials, the advantages of the $h$-BN-based magnetic sensor described in this work are its ease of use, high flexibility, and, more importantly, its ability to be placed in close proximity to a target sample. Such a sensing unit will likely find numerous applications in 2D materials research by offering a simple way to probe the physics of van der Waals heterostructures.

• Received 21 July 2022
• Revised 17 October 2022
• Accepted 23 November 2022

DOI:https://doi.org/10.1103/PhysRevApplied.18.L061002