Quantum Sensing of Magnetic Materials by Spin Defects in Hexagonal Boron Nitride*

Optically active quantum spin defects contained in wide band-gap semiconductors have been demonstrated as a sensitive probe to investigate local electromagnetic property of condensed matter systems. Novel spin defects in van der Waals two-dimensional (2D) crystals are naturally relevant in this context due to their significantly improved compatibility with nanodevice integration and atomic length scale proximity readily established between the spin sensors and objects of interest. Taking advantage of boron vacancy spin defects in hexagonal boron nitride (hBN), we report nanoscale quantum sensing and imaging of static and dynamic magnetic field environment of low-dimensional magnetic materials under a broad range of experimental conditions. Our results highlight the appreciable capability of 2D spin defects of evaluating local magnetic properties of solid-state materials in an accessible and precise way, which can be extended readily to a broad family of quantum materials and devices.