Occupancy disorder in the magnetic topological insulator candidate Mn1-xSb2+xTe4

Abstract

MnSb2Te4 is a candidate magnetic topological insulator exhibiting more pronounced cation intermixing than its predecessor MnBi2Te4. Investigating the cation intermixing and its possible implications on the magnetic order in MnSb2Te4 are currently hot topics in research on quantum materials for spintronics and energy-saving applications. Two single-crystal X-ray diffraction measurements of Mn1-x Sb2+x Te4 (x = 0.06 and x =-0.1) are presented alongside a detailed discussion of its crystal structure with a spotlight on the apparent occupancy disorder between the two cations. This disorder has been noted by other groups as well, yet never been analyzed in-depth with single-crystal X-ray diffraction. The latter is the tool of choice to receive a meaningful quantification of antisite disorder. Between the two synthesis procedures we find subtle differences in phases and/or alternation of the cation content which has implications on the magnetic order, as illustrated by bulk magnetometry. Understanding and assessing this disorder in magnetic topological insulators of the MnX2Te4 (X = Bi, Sb) type is crucial to gauge their applicability for modern spintronics. Furthermore, it opens new ways to tune the "chemical composition-physical property"relationship in these compounds, creating an alluring aspect also for fundamental science.