Vapor transport growth of MnBi2Te4 and related compounds

TL;DR

This study demonstrates vapor transport methods for growing MnBi2Te4 and related compounds, enabling fine control over their magnetic and topological properties through defect engineering and compositional tuning.

Contribution

It introduces a vapor transport growth technique for MnBi2Te4 and related compounds, offering an alternative to flux growth with better stoichiometry control and potential for property tuning.

Findings

Vapor transport effectively grows MnBi2Te4 crystals within 500-590°C.

Iodides accelerate chemical transport compared to chlorides.

Vapor transported crystals are more Mn-stoichiometric and show more site mixing in Sb-doped variants.

Abstract

Motivated by fine tuning of the magnetic and topological properties of MnBi$_2$Te$_4$ via defect engineering, in this work, we report the crystal growth of MnBi$_2$Te$_4$ and related compounds using vapor transport method and characterization of vapor transported crystals by measuring elemental analysis, magnetic and transport properties, and scanning tunneling microscopy. For the growth of MnBi$_2$Te$_4$ single crystals, I$_2$, MnI$_2$ , MnCl$_2$, TeCl$_4$, or MoCl$_5$ are all effective transport agents; chemical transportation occurs faster in the presence of iodides than chlorides. MnBi$_2$Te$_4$ crystals can be obtained in the temperature range 500$^\circ$C-590$^\circ$C using I$_2$ as the transport agent. We further successfully grow MnSb$_2$Te$_4$, MnBi$_{2-x}$Sb$_x$Te$_4$, and Sb-doped MnBi$_4$Te$_7$ crystals. A small temperature gradient $<$20$^\circ$C between the hot and cold ends of the growth cmpoule is critical for the successful crystal growth of MnBi$_2$Te$_4$ 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.