Realization of a spin glass in a two-dimensional van der Waals material.

Recent advances in van der Waals materials have sparked renewed interest in the impact of dimensionality on magnetic phase transitions. Although ordered magnetic phases have been demonstrated to survive in the two-dimensional (2D) limit, the quest for a spin glass with quenched magnetic disorder in lower dimensions has proven elusive. Here, we provide evidence of a spin glass emerging from randomly distributed Fe atoms in Fe3GeTe2 (FGT). ac magnetic susceptibility displays a strong frequency dependence indicative of slow spin dynamics. Additional distinctive phenomena, including aging, chaos, and memory effects, further substantiate the existence of a glassy state. Notably, we found that this state persists even in single-cell-thick FGT, thereby confirming the existence of a 2D spin glass.