Evidence of non-collinear spin texture in magnetic moiré superlattices

Moiré magnetism is emerging as a platform to design and control exotic magnetic phases in twisted magnetic two-dimensional crystals. Non-collinear spin texture emerging from twisted two-dimensional magnets with collinear spins is one of the most profound consequences of moiré magnetism and forms the basis for realizing non-trivial magnetic orders and excitations. However, no direct experimental observations of non-collinear spins in moiré magnets have been made, despite recent theoretical and experimental efforts. Here, we report evidence of non-collinear spin texture in two-dimensional twisted double bilayer CrI 3 . We distinguish the non-collinear spins with a gradual spin flop process from the collinear spins with sudden spin flip transitions and identify a net magnetization emerging from the collinear spins. We also demonstrate that both non-collinear spins and net magnetization are present at twist angles from 0.5° to 5° but are most prominent for 1.1°. We resolve a critical temperature of 25 K for the onset of the net magnetization and the softening of the non-collinear spins in the 1.1° samples. This is substantially lower than the Néel temperature of 45 K for natural few layers. Our results provide a platform to explore non-trivial magnetism with non-collinear spins.