Magnetic Dynamics in van der Waals Magnets Probed by Time-Resolved Magneto-Optics

The recently discovered atomically-thin magnetic crystals provide a unique playground for understanding magnetization in 2D confinement and developing new approaches to manipulating magnetism for novel spintronic devices. In this talk, I focus on our recent works of time-resolved spin dynamics in 2D magnetic crystals, including CrI₃ and FePS₃. Ultrafast optical pulse excitations are used to create non-equilibrium states and launch magnon modes, and we analyze the subsequent magnetization relaxations with sub-picosecond time-resolution. The first half of the talk will focus on the coherent magnons in bilayer CrI₃. The observed magnon frequencies correspond to the antiferromagnetic resonance, and can be further tuned with electrostatic gating. In the second half of the talk, I will discuss the diverging spin dynamics in few-layered FePS₃, which can be attributed to the critical behaviors near the Neel transition temperature.