Vapor transport growth of MnBi2Te4 and related compounds

Abstract

Motivated by fine tuning of the magnetic and topological properties of MnBi2Te4 via defect engineering, in this work, we report the crystal growth of MnBi2Te4 and related compounds using vapor transport method and crystal characterization by measuring elemental ratio, magnetic and transport properties, and scanning tunneling microscopy. For the growth of MnBi2Te4 single crystals, I2, MnI2 , MnCl2, TeCl4, and MoCl5 are all effective transport agents; chemical transportation occurs faster in the presence of iodides than chlorides. MnBi2Te4 crystals can be obtained in the temperature range 500 • C-590 • C using I2 as the transport agent. We further successfully grow MnSb2Te4, MnBi2−xSbxTe4, and Sb-doped MnBi4Te7 crystals. A small temperature gradient <20 • C between the hot and cold ends of the growth cmpoule is critical for the successful crystal growth of MnBi2Te4 and related compounds. Compared to flux grown crystals, vapor transported crystals tend to be Mn stoichiometric, and Sb-bearing compositions have more Mn/Sb site mixing. The vapor transport growth provides a new materials synthesis approach to fine tuning the magnetic and topological properties of these intrinsic magnetic topological insulators.

The elusive quantum anomalous Hall effect in MnBi2Te4: a materials perspective

“…Defect engineering: The presence and abundance of lattice defects make possible the fine tuning of the magnetism and the electronic band structure of MnBi 2 Te 4 and related compounds by controlling the type, concentration, and distribution of lattice defects. At this time, it is known that MnBi 2 Te 4 crystals with the least or no Bi M n facilitates the observation of Chern insulator state under high magnetic fields [21]. The transport results in Ref.…”

“…Ge and Pb substitutions are expected to play a similar role. Vapor transport [21] and solid state syntheses of Cr-and V-doped MnBi 2 Te 4 efforts were in vain.…”

“…Currently available MnBi 2 Te 4 crystals grown out of Bi 2 Te 3 flux [23] and those by chemical vapor transport technique [21,24] have comparable amount of Mn Bi because in both syntheses the crystallization occurs in a narrow temperature window of 500-600 • C. This indicates the importance of thermodynamics over the kinetics for the formation of Mn Bi in this temperature range. Further advancements in crystal growth are needed to vary the growth temperature in a wider range or the growth mechanism thus to control the population and distribution of Mn Bi .…”