Phase-pure two-dimensional Fe_xGeTe₂ magnets with near-room- temperature T_C

Two-dimensional (2D) ferromagnets with out-of-plane (OOP) magnetic anisotropy are potential candidates for realizing the next-generation memory devices with ultra-low power consumption and high storage density. However, a scalable approach to synthesize 2D magnets with OOP anisotropy directly on the complimentary metal-oxide semiconductor (CMOS) compatible substrates has not yet been mainly explored, which hinders the practical application of 2D magnets. This work demonstrates a cascaded space confined chemical vapor deposition (CS-CVD) technique to synthesize 2D Fe_xGeTe₂ ferromagnets. The weight fraction of iron (Fe) in the precursor controls the phase purity of the as-grown Fe_xGeTe₂. As a result, high-quality Fe₃GeTe₂ and Fe₅GeTe₂ flakes have been grown selectively using the CS-CVD technique. Curie temperature (T_C) of the as-grown Fe_xGeTe₂ can be up to ~ 280 K, nearly room temperature. The thickness and temperature-dependent magnetic studies on the Fe₅GeTe₂ reveal a 2D Ising to 3D XY behavior. Also, Terahertz spectroscopy experiments on Fe₅GeTe₂ display the highest conductivity among other Fe_xGeTe₂ 2D magnets. The results of this work indicate a scalable pathway for the direct growth and integration of 2D ternary magnets on CMOS-based substrates to develop spintronic memory devices.