Rich behaviors of magnetic excitations in a two-dimensional honeycomb Ising magnet CrI₃

Two-dimensional (2D) magnetism has been long sought-after, and only very recently realized in atomic crystals of magnetic van der Waals materials. So far, a comprehensive understanding of the magnetic excitations in such 2D magnets remain to be fully explored and comprehensively understood. In this talk, we report polarized micro-Raman spectroscopy studies on a 2D honeycomb magnet CrI3. We will show the presence of two types of magnetic excitations in 2D CrI3, one being the spin waves (i.e., magnons) and the other being a static-magnetism-phonon coupled entity. By exploring their symmetry properties and temperature dependence, we confirm the magnetic nature of both types of excitations. By performing layer number and magnetic field dependent Raman measurements, we show the rich behaviors of both excitations across the phase transition from the layered antiferromagnetic to ferromagnetic order. These results of two types of magnetic excitations demonstrate the intriguing magnetic properties and intricate interplay between spin and lattice in 2D magnets, thus opening up opportunities for spintronics incorporating 2D magnets.