Phase-Controlled Growth of Two-Dimensional Magnetic Chromium Tellurides

The discovery of ferromagnetic ordering in two-dimensional (2D) materials has sparked significant interest in both academic and industrial communities for its great potential in fundamental research and novel application such as spintronics. Recently, chromium tellurides (Cr_xTe_y) with various phases and compositions, are emerging as a promising class of novel 2D ferromagnets, attributed to their tunable magnetic ordering, high Curie temperature (T<i>_C</i>), and desirable stability. It is believed that the rich structural and magnetic variations of Cr_xTe_y should arise from the position and content of the intercalated Cr atoms between adjacent layers. However, the synthesis of ultrathin and high-quality Cr_xTe_y with controlled phases and compositions is challenging, not to mention the in-depth investigation of the effect of intercalated Cr atoms on magnetic ordering. In this work, by carefully tuning the reaction temperature and carrier gas flow rate, controllable growth of various Cr_xTe_y, including CrTe, Cr₂Te₃, Cr₅Te₈, and CrTe₂, is achieved with the facile one-step chemical vapor deposition (CVD) method. Atomic-resolution scanning transmission electron microscopy-annular dark field imaging is adopted to unravel the phases of as-synthesized Cr_xTe_y. Magnetic properties of prepared Cr_xTe_y are probed using both reflective magnetic circular dichroism and magnetotransport measurements. Near-rectangular hysteresis loops not only indicate ferromagnetism with strong magnetic anisotropy in all Cr_xTe_y flakes but also suggest the high quality of the CVD-grown samples. Remarkably, the strong correlation between phase and magnetic ordering of Cr_xTe_y is comprehensively studied and reported for the first time. Density functional theory calculations further reveal the difference in ferromagnetic ordering between various phases, which can be well interpreted by the magnetic anisotropy and Stoner criterion. This work sheds light on the scalable and controllable synthesis of 2D magnetic materials and highlights the great potential of Cr_xTe_y for future spintronic applications.