Magnetic Phase Transition in Two-Dimensional CrBr_3 Probed by a Quantum Sensor

Recently, magnetism in two-dimensional (2D) van der Waals (vdW) materials has attracted wide interests. It is anticipated that these materials will stimulate discovery of new physical phenomena and novel applications. The capability to quantitatively measure the magnetism of 2D magnetic vdW materials is essential to understand these materials. Here we report on quantitative measurements of ferromagnetic-to-paramagnetic phase transition of an atomically thin (down to 11 nm) vdW magnet, namely CrBr_3, with a Curie point of 37.5 K. This experiment demonstrates that surface magnetism can be quantitatively investigated, which is useful for a wide variety of potential applications.