Chemical Vapor Deposition and Raman Spectroscopy of Two-Dimensional Antiferromagnetic FeOCl Crystals

Chemical vapor deposition (CVD) and probing magnetic properties of atomically thin two-dimensional (2D) materials are of great interest for future information devices. Here, we report a CVD growth of 2D FeOCl crystals and a Raman spectroscopic study of the magnetic phase transition. 2D FeOCl crystals with different thicknesses have been grown on mechanically exfoliated h-BN by using KMnO4 and FeCl3 as precursors. Raman scattering has been conducted on the chemically grown FeOCl thin crystals, which can probe the magnetic orderings in various ways, such as quasi-particle scattering, quasi-elastic scattering (QES), magneto-optical effect, and so on. Under an external magnetic field, the Ag phonon modes have shown a linear relationship of B/rho to B2 (B is the external magnetic field and rho is the degree of Raman circular polarization), which supports the calculated magnetic point group of m ' m ' m in FeOCl thin crystals below TN. Other magnetic Raman features, including quasi-elastic scattering and two-magnon scattering, have been observed, which gives information about the magnetic specific heat and magnetic excitations, respectively. At last, temperature-dependent and thickness-dependent Raman spectroscopic measurements have shown a robust paramagnetic-antiferromagnetic (PM-AFM) phase transition in FeOCl thin crystals.