Spin fluctuations and magneto-elastic coupling in the ferromagnetic van der Waals semiconductor CrSiTe3

The transition metal trichalcogenide CrSiTe3 is a layered van der Waals semiconductor that has recently been proposed to retain its long-range ferromagnetic order even in the atomically thin limit. Here we examine the nature of the bulk ferromagnetic phase transition using a suite of static and time-resolved optical probes including second harmonic generation, magneto-optical Kerr rotation and optical reflectivity. We show that strong magnetic fluctuations persist far above the Curie temperature, attesting to the strong two-dimensional character of ferromagnetism even in bulk crystals. We also identify strong coupling between the ferromagnetism and specific phonon modes.