Occupancy disorder in the magnetic topological insulator candidate Mn1−x Sb2+x Te4

Laura C Folkers,Fabian Lukas,Anja U B Wolter,Anna Isaeva,Manaswini Sahoo,Laura Teresa Corredor

doi:10.1515/zkri-2021-2057

Abstract

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.

Highlights

Today’s materials science is driven by the pursuit of novel functional materials to allow for e.g. the ongoing development of computing and energy-saving technologies
Our interest lies in the pursuit of topological materials, which allow for a dissipationless spin transport on their surfaces, that is not disturbed by structural imperfections or inclusions [1,2,3]
The current even hotter than hot topic is to combine longrange magnetic order – a bulk property – with the topologically protected transport – a surface property – and have them influence each other. This has been first achieved in Crx(Bi,Sb)2Te3, which was the artificial heterostructure on which the quantum anomalous hall effect (QAHE) was discovered [5]

Summary

Introduction

Today’s materials science is driven by the pursuit of novel functional materials to allow for e.g. the ongoing development of computing and energy-saving technologies These functional materials encompass for instance multiferroics, high-temperature superconductors and topologically non-trivial materials, i.e. materials exhibiting unconventional combinations of electronic conductivity and magnetism. The current even hotter than hot topic is to combine longrange magnetic order – a bulk property – with the topologically protected transport – a surface property – and have them influence each other. This has been first achieved in Crx(Bi,Sb)2Te3, which was the artificial heterostructure on which the quantum anomalous hall effect (QAHE) was discovered [5]. The present study explores the Mn/Sb intermixing in two distinct Mn1−xSb2+xTe4 crystals and its implications for magnetism

Experimental

Structural studies

Findings

Magnetic studies