Crystal Growth and Characterization of Possible New Magnetic Topological Insulators FeBi₂Te₄

Here, we report successful single crystal growth of new possible magnetic topological insulator (MTI) FeBi₂Te₄ by a self-flux method via a vacuum encapsulation process. The detailed Rietveld analysis of powder XRD data shows the as-grown MTI crystal to be mainly dominated by the FeBi₂Te₄ phase along with minority phases of Bi₂Te₃ and FeTe. Scanning electron microscope (SEM) image shows the morphology of as-grown MTI single crystal to be of layered type laminar structure. Raman spectroscopy of the crystal exhibited three distinct phonon modes at 65, 110, and 132 cm⁻¹ along with two split secondary modes at 90, and 144 cm⁻¹. The secondary split modes are the result of FeTe intercalation in the Bi₂Te₃ unit cell. Magnetoresistance (MR%) measurement has been performed at different temperatures, i.e., 200 K, 20 K, and 2 K in applied magnetic fields up to ± 12 Tesla, which showed very low MR in comparison with pure Bi₂Te₃ crystal. Temperature dependence of DC magnetization measurements shows the FeBi₂Te₄ crystal to be mainly of ferromagnetic (FM) or ferrimagnetic nature above 295 K, albeit a secondary weak magnetic transition is seen at 54–46 K as well. Detailed isothermal magnetization (MH) results showed that the FM saturation moment at 295 K is 0.00213 emu/g, which is nearly invariant until 400 K. In summary, we had grown an MTI FeBi₂Te₄ single crystal, which may be a possible entrant for the quantum anomalous Hall (QAH) effect at room temperature or above.