Probing Low Energy Spin-Excitations in Multilayer Chromium Trihalides with Nitrogen-Vacancy Centers in Diamond

Chromium trihalides are Van der Waals magnets that can be exfoliated down to monolayer. They therefore serve as a model system to study magnetism in low dimensions. However, given the small sample volume of multilayers and their weak signal strength, the dynamical properties are hard to explore experimentally. Here we report the use of nitrogen-vacancy (NV) centers in diamond, which are highly sensitive, local magnetic sensors, to probe the low energy excitations in these systems.