cm8b05017_si_001.pdf (2.85 MB)
Chemical Aspects of the Candidate Antiferromagnetic Topological Insulator MnBi2Te4
journal contribution
posted on 2019-04-02, 17:48 authored by Alexander Zeugner, Frederik Nietschke, Anja U. B. Wolter, Sebastian Gaß, Raphael C. Vidal, Thiago R. F. Peixoto, Darius Pohl, Christine Damm, Axel Lubk, Richard Hentrich, Simon K. Moser, Celso Fornari, Chul Hee Min, Sonja Schatz, Katharina Kißner, Maximilian Ünzelmann, Martin Kaiser, Francesco Scaravaggi, Bernd Rellinghaus, Kornelius Nielsch, Christian Hess, Bernd Büchner, Friedrich Reinert, Hendrik Bentmann, Oliver Oeckler, Thomas Doert, Michael Ruck, Anna IsaevaHigh-quality single
crystals of MnBi2Te4 are
grown for the first time by slow cooling within a narrow range between
the melting points of Bi2Te3 (586 °C) and
MnBi2Te4 (600 °C). Single-crystal X-ray
diffraction and electron microscopy reveal ubiquitous antisite defects
in both cation sites and, possibly, Mn vacancies (Mn0.85(3)Bi2.10(3)Te4). Thermochemical studies complemented
with high-temperature X-ray diffraction establish a limited high-temperature
range of phase stability and metastability at room temperature. Nevertheless,
the synthesis of MnBi2Te4 can be scaled-up as
powders can be obtained at subsolidus temperatures and quenched at
room temperature. Bulk samples exhibit long-range antiferromagnetic
ordering below 24 K. The Mn(II) out-of-plane magnetic state is confirmed
by the magnetization, X-ray photoemission, X-ray absorption, and linear
dichroism measurements. The compound shows a metallic type of resistivity
in the range 4.5–300 K and is an n-type conductor that reaches
a thermoelectric figure of merit up to ZT = 0.17.
Angle-resolved photoemission experiments show a surface state forming
a gapped Dirac cone, thus strengthening MnBi2Te4 as a promising candidate for the intrinsic magnetic topological
insulator, in accordance with theoretical predictions. The developed
synthetic protocols enable further experimental studies of a crossover
between magnetic ordering and nontrivial topology in bulk MnBi2Te4.