Controlled Synthesis of a Two-Dimensional Non-van der Waals Ferromagnet toward a Magnetic Moiré Superlattice.

ABSTRACT

Two-dimensional (2D) magnetic materials provide an ideal platform for spintronics, magnetoelectrics, and numerous intriguing physical phenomena in 2D limits. Moiré superlattices based on 2D magnets offer an avenue for controlling the spin degree of freedom and engineering magnetic properties. However, the synthesis of high-quality, large-grain, and stable 2D magnets, much less obtaining a magnetic moiré superlattice, is still challenging. We synthesize 2D ferromagnets (trigonal Cr5Te8) with controlled thickness and robust stability through chemical vapor deposition. Single-unit-cell-thick flakes with lateral sizes of tens of micrometers are obtained. We observe the layer-by-layer growth mode for the crystal formation in non-van der Waals Cr5Te8. The robust anomalous Hall signal confirms that Cr5Te8 of varying thickness have a long-range ferromagnetic order with an out-of-plane easy axis. There is no obvious change of the Curie temperature when the thickness of Cr5Te8 decreases from 52.1 to 7.2 nm. Here, we construct diverse 2D non-van der Waals/van der Waals vertical heterostructures (Cr5Te8/graphene, Cr5Te8/h-BN, Cr5Te8/MoS2). A uniform moiré superlattice is formed in the heterostructure through a lattice mismatch. The successful growth of 2D Cr5Te8 and a related moiré superlattice introduces 2D non-van der Waals ferromagnets into moiré superlattice research, thus highlighting prospects for property investigation of a non-van der Waals magnetic moiré superlattice and massive applications which require a scalable approach to magnetic moiré superlattices.