Epitaxial Growth and Structural Characterizations of MnBi 2 Te 4 Thin Films in Nanoscale.

The intrinsic magnetic topological insulator MnBi 2 Te 4 has attracted much attention due to its special magnetic and topological properties. To date, most reports have focused on bulk or flake samples. For material integration and device applications, the epitaxial growth of MnBi 2 Te 4 film in nanoscale is more important but challenging. Here, we report the growth of self-regulated MnBi 2 Te 4 films by the molecular beam epitaxy. By tuning the substrate temperature to the optimal temperature for the growth surface, the stoichiometry of MnBi 2 Te 4 becomes sensitive to the Mn/Bi flux ratio. Excessive and deficient Mn resulted in the formation of a MnTe and Bi 2 Te 3 phase, respectively. The magnetic measurement of the 7 SL MnBi 2 Te 4 film probed by the superconducting quantum interference device (SQUID) shows that the antiferromagnetic order occurring at the Néel temperature 22 K is accompanied by an anomalous magnetic hysteresis loop along the c -axis. The band structure measured by angle-resolved photoemission spectroscopy (ARPES) at 80 K reveals a Dirac-like surface state, which indicates that MnBi 2 Te 4 has topological insulator properties in the paramagnetic phase. Our work demonstrates the key growth parameters for the design and optimization of the synthesis of nanoscale MnBi 2 Te 4 films, which are of great significance for fundamental research and device applications involving antiferromagnetic topological insulators.