Two-dimensional air-stable non-layered ferrimagnetic FeCr2 S4 crystals synthesized via chemical vapor deposition.

The discovery of intrinsic two-dimensional (2D) magnetic materials has opened up new opportunities for exploring magnetic properties at atomic layer thicknesses, presenting potential applications in spintronic devices. Here we have synthesized a new 2D ferrimagnetic crystal of non-layered FeCr2 S4 with high phase purity using chemical vapor deposition. The obtained 2D FeCr2 S4 exhibited perpendicular magnetic anisotropy, as evidenced by the out-of-plane/in-plane Hall effect and anisotropic magnetoresistance. Theoretical calculations further elucidated that the observed magnetic anisotropy can be attributed to its surface termination structure. By combining temperature-dependent magneto-transport and polarized Raman spectroscopy characterizations, we also discovered that both the measured Curie temperature and the critical temperature at which a low energy magnon peak disappeared remained constant, regardless of its thickness. Magnetic force microscopy measurements showed the flipping process of magnetic domains. The exceptional air-stability of the 2D FeCr2 S4 was also confirmed via Raman spectroscopy and Hall hysteresis loops. The robust anisotropic ferrimagnetism, the thickness-independent of Curie temperature, coupled with excellent air-stability, make 2D FeCr2 S4 crystals highly attractive for future spintronic devices. This article is protected by copyright. All rights reserved.