Controllable Chemical Vapor Deposition Synthesis and Second-Harmonic Generation of Rhombohedral Cr₂S₃

Non-layered two-dimensional (2D) chromium-based chalcogenides have garnered significant attention due to their distinctive magnetic, electronic, and optical properties. In this work, we report the controllable synthesis of high-quality rhombohedral Cr₂S₃ nanosheets on mica substrates via an atmospheric pressure chemical vapor deposition (CVD) strategy. The as-grown rhombohedral Cr₂S₃ nanosheets exhibit pronounced optical second-harmonic generation (SHG) signals, which show thickness-dependent enhancement and a strong dependence on both the linear excitation and detection polarization configurations. Most notably, temperature-dependent SHG measurements reveal a distinct inflection point near the Néel temperature (T_N ≈ 120 K), where the SHG intensity exhibits a sharp enhancement upon cooling below T_N. This behavior arises from the additional magnetic dipole contributions activated by magnetic ordering, establishing SHG as a sensitive probe of magnetic phase transitions in non-layered 2D magnetic materials. Furthermore, circularly polarized SHG signals exhibit nearly 100% circular polarization at low temperatures. This work systematically elucidates the nonlinear optical response characteristics of rhombohedral Cr₂S₃ and their correlation with magnetic ordering transitions, laying an experimental foundation for the application of 2D non-van der Waals magnetic materials in nonlinear optoelectronics and spin-optoelectronic devices.