Physical Vapor Transport Growth of Antiferromagnetic CrCl$_3$ Flakes Down to Monolayer Thickness

Abstract

The van der Waals magnets CrX$_3$ (X = I, Br, and Cl) exhibit highly tunable magnetic properties and are promising candidates for developing novel two-dimensional (2D) magnetic devices such as magnetic tunnel junctions and spin tunneling transistors. Previous studies of CrCl$_3$ have mainly focused on mechanically exfoliated samples. Controlled synthesis of high quality atomically thin flakes is critical for their technological implementation but has not been achieved to date. Here, we report the growth of large CrCl$_3$ flakes with well-defined facets down to monolayer thickness (~0.6 nm) via the physical vapor transport technique. Both isolated flakes with well-defined facets and long stripe samples with the trilayer portion exceeding 60 $\mu$m have been obtained. High-resolution transmission electron microscopy studies show that the CrCl$_3$ flakes are single crystalline in the monoclinic structure, consistent with the Raman results. The room temperature stability of the CrCl$_3$ flakes decreases with decreasing thickness. The tunneling magnetoresistance of graphite/CrCl$_3$/graphite tunnel junctions confirms that few-layer CrCl$_3$ possesses in-plane magnetic anisotropy and N\'eel temperature of 17 K. Our study paves the path for developing CrCl$_3$-based scalable 2D spintronic applications.